Instructions for objconv
A utility for cross-platform development of function libraries, for convertingand modifying object files and for dumping and disassembling object andexecutable files for all x86 and x86-64 platforms.
Version 2.54. By Agner Fog © 2006-2022.
GNU General Public License v. 3 or later.

Contents
1 Introduction ....................................................................................................................... 2
1.1 File types .................................................................................................................... 3
2 Command line syntax ........................................................................................................ 4
3 Warning and error control .................................................................................................. 6
4 Converting file formats ...................................................................................................... 6
5 Modifying symbols ............................................................................................................. 7
6 Managing libraries ............................................................................................................. 87 Dumping files .................................................................................................................. 10
8 Disassembling files.......................................................................................................... 10
8.1 How to interpret the disassembly .............................................................................. 11
8.2 Compatibility problems.............................................................................................. 13
8.3 Using the disassembler for checking machine code .................................................. 14
8.4 Assembly syntax for AVX-512 and Knights Corner instructions ................................ 14
9 Converting assembler-generated files ............................................................................. 16
10 Converting compiler-generated files .............................................................................. 18
10.1 Call stubs for 64-bit conversions ............................................................................. 20
11 Frequently asked questions ........................................................................................... 2211.1 Why is there no graphical user interface? ............................................................... 2211.2 What kind of files can objconv convert? .................................................................. 2211.3 Is it possible to convert files for ARM? .................................................................... 23
11.4 Is it possible to convert files for PPC or other architectures?................................... 23
11.5 Is it possible to link converted files into Borland Delphi Pascal? .............................. 23
11.6 Can I convert an executable file from one system to another? ................................ 23
11.7 Can I convert from 32 bit code to 64 bit code? ........................................................ 23
11.8 Can I convert a dynamic link library to another system?.......................................... 23
11.9 Can I build a function library that works in all operating systems? ........................... 24
11.10 Why can't I convert an export library? ................................................................... 24
11.11 Can I convert a static library to a dynamic library? ................................................ 24
11.12 Can I convert a dynamic library to a static library? ................................................ 24
11.13 Can I convert a Windows function library to use it under Linux?............................ 24
11.14 Can I convert a Linux function library to use it under Windows?............................ 24
11.15 I want to know which library contains a particular function .................................... 24
11.16 How do I know if my Linux function uses the red zone? ........................................ 24
11.17 How do I know if my Linux function has position-independent code ...................... 25
11.18 I have problems porting my Windows application to Linux because the Gnu
compiler has a more strict syntax. Can I convert the compiled Windows code instead?.. 25
11.19 Is it possible to extract one or more functions from a binary file or program? ........ 25
11.20 Is it possible to convert mangled function names? ................................................ 25
11.21 Is it possible to convert function calling conventions automatically? ...................... 25
11.22 Does the disassembler have an interactive feature? ............................................. 26
11.23 Is it possible to disassemble an executable file to modify it and then assemble itagain?............................................................................................................................. 26
11.24 Is it possible to disassemble an object file and fix all compatibility problems
manually? ....................................................................................................................... 26
11.25 Is it possible to reconstruct C++ code from a disassembly? .................................. 26
11.26 Why do I get error messages in the disassembly file? ........................................... 26
11.27 How does the disassembler distinguish between code and data? ......................... 26

11.28 Can I disassemble byte code? .............................................................................. 27
11.29 Can I assemble the output of the disassembler? ................................................... 27
11.30 Why does the disassembler not support AT&T syntax? ........................................ 27
11.31 How can I convert assembly syntax? .................................................................... 27
11.32 Why does my disassembly take so long time? ...................................................... 27
11.33 How can I save the output of the dump screen to a file? ....................................... 28
11.34 Can you help me with my problems? .................................................................... 28
11.35 Are there any alternatives to objconv? .................................................................. 28
12 Warning and error messages ........................................................................................ 28
12.1 Linker errors:........................................................................................................... 29
13 Source code .................................................................................................................. 30
13.1 Explanation of the objconv source code .................................................................. 30
13.2 How to add support for new file formats .................................................................. 32
13.3 How to add features to the disassembler ................................................................ 32
13.4 File list .................................................................................................................... 33
13.5 Class list ................................................................................................................. 34
14 Legal notice ................................................................................................................... 37

1 Introduction
Objconv is a utility for facilitating cross-platform development of function libraries, forconverting and disassembling object files, and for other development purposes. The latest
version of objconv is available at www.agner.org/optimize.
Objconv can perform the following tasks:•

Convert object files between different formats used on different x86 and x86-64
platforms.

•

Change symbol names in object files.

•

Build, manage and convert static link libraries in various formats for different x86 andx86-64 platforms.

•

Dump file headers and other contents of object files, static and dynamic library files,
and executable files.

•

Disassemble object files and executable files and check instruction code syntax.

The following platforms are supported:•

Windows, 32 and 64 bit x86.

•

Linux, 32 and 64 bit x86.

•

BSD, 32 and 64 bit x86.

•

Mac OS X, 32 and 64 bit x86 (Darwin, Intel based).

The latter three platforms are all based on the UNIX heritage. I will use "Unix" as a common
name for Linux, BSD and Mac on x86 an x86-64 platforms in this manual.
The source code for objconv can be compiled and run under any of these platforms. The
program is compatible with standard make utilities.
Note that objconv is intended for programming experts. It is far from fool proof, and you
need to have a very good understanding of how compilers and linkers work in order to use
2this program. Please do not send your programming questions to me - you will not get any
answer.

1.1 File types
An executable file is a file containing machine code that can be executed. This can be a
program file or a dynamic link library, also called shared object. The name shared object isused only in Unix-like systems, such as Linux, BSD and Mac OS X.
An object file is an intermediate file used in the building of an executable file. It contains partof the code that will make up the final executable file. An object file usually contains crossreferences to functions in other object files.
A static link library means a collection of object files. This is called a static linking library filein Windows terminology or an archive in Unix terminology. I prefer to use the name librarybecause an archive can also mean a .zip or .tar file.
Objconv cannot modify or convert executable files, including dynamic link libraries or sharedobjects, but it can dump or disassemble such files.
The following table summarizes the type of operations that objconv can do on various filetypes:
File type andformatObject file
COFF/PE
Library file
COFF/PE
DLL, driver
COFF/PE
Executable file
COFF/PE
Object file
OMF
Object file
OMF
Library file
OMF
Library file
OMF
Executable file
16 bitObject file
ELF
Library file
ELF
Shared Object
ELF
Executable file
ELF
Object fileMach-O
Library fileMach-O
Shared object
Mach-O
Executable fileMach-O
Universal

Wordsize, bits
32, 64

Exten- Operatingsion
system.obj
Windows

ModifyDumpxxDisassemblex32, 64.libWindows

x

x

x

x

x

32, 64

Windows

32, 64

.dll,
.sys
.exe

-

-

-

x

x

Windows

-

-

-

x

x

16

.obj

DOS, Windows 3.x
Windows

-

-

-

x

x

32

.obj

x

x

x

x

x

16

.lib

-

-

x

x

x

32

.lib

x

x

x

x

x

16

.exe

32, 64

DOS, Windows 3.x
Windows

Convert Convert
from
to
x
x

-

-

-

-

-

.o

DOS, Windows 3.x
Linux, BSD

x

x

x

x

x

32, 64.aLinux, BSD

x

x

x

x

x

32, 64.soLinux, BSD

-

-

-

x

x

Linux, BSD

-

-

-

x

x

32, 6432, 64.o

Mac OS X

x

x

x

x

x

32, 64.a

Mac OS X

x

x

x

x

x

32, 64.so

Mac OS X

-

-

-

x

x

32, 64

Mac OS X

-

-

-

x

x

32, 64

Mac OS X

-

-

-

x

x

3

binary

2 Command line syntax
If you want to run objconv under one of the Unix systems (Linux, BSD, Mac), then you haveto first build the executable. Unpack source.zip to a temporary directory and run the build
script build.sh. To run objconv under Windows, you can just use the executableobjconv.exe.
Objconv is executed from a command line or from a make utility. The syntax is as follows:
objconv options inputfile [outputfile]
Options start with a dash -. A slash / is accepted instead of - when running underWindows. Options must be separated by spaces. The order of the options is arbitrary, but all
options must come before inputfile. The name of the output file must be different fromthe input file, except when adding object files to a library file. The option letters are caseinsensitive, file names and symbol names are case sensitive.
The return value from objconv is zero on success, and equal to the highest error number incase of error. This will stop a make utility in case of error messages, but not in case of
warning messages.

Summary of options-fXXX

Convert file to format XXX. XXX = coff, omf, elf or mac.
pe is accepted as a synonym for coff. The word size, 32 or 64, may beappended to the name, e.g. elf64.

-fasm

Disassemble file. Variants for different assembly syntax dialects:-fmasm, -ftasm, -fnasm, -fyasm, -fgasm.

-dXXX

Dump contents of file. XXX can be one or more of the following:
f: file header, h: section headers, s: symbol table,
r: relocation table, n: string table (all names).

-xs

Strip exception handling information and other incompatible info. (Default
when converting to a different format).

-xp

Preserve exception handling information and other incompatible info.

-nuChange leading underscores on symbol names to the default for the target
system.

-nu-

Remove leading underscores from symbol names.

-nu+

Add leading underscores to symbol names.

-au-Remove leading underscores from public symbol names and keep old names
as aliases.

-au+

Add leading underscores to public symbol names and keep old names as
aliases.
4

-nd

Replace leading dot or underscore in section names with the default for
the target system.

-nr:N1:N2

Replace name N1 with N2. N1 may be a symbol name, section nameor library member name.

-np:N1:N2

Replace symbol prefix N1 with N2. N1 may be the beginning of a symbolname or section name.

-ns:N1:N2

Replace symbol suffix N1 with N2. N1 may be the end of a symbol name or
section name.

-ar:N1:N2

Give public symbol N1 an alias name N2. The same symbol will beaccessible as N1 as well as N2.

-ap:N1:N2

Replace symbol prefix N1 with N2 and retain the old name as an alias.

-as:N1:N2

Replace symbol suffix N1 with N2 and retain the old name as an alias.

-nw:N1Make public symbol N1 weak. Only possible for ELF files and 64-bit Mach-O
files.

-nl:N1Make public or external symbol N1 local (invisible).

-lx

Extract all members from library inputfile to object files.

-lx:N1:N2

Extract member N1 from library and save it as object file N2. The nameof the object file will be N1 if N2 is omitted. May use | instead of : asseparator.

-la:N1:N2

Add object file N1 to library and give it member name N2. The member
name will be N1 if N2 is omitted. May use | instead of :.

-ld:N1

Delete member N1 from library.

-ls

Shorten long library member names. There are several different ways ofstoring member names longer than 15 characters in a library file. This option
makes sure that no names are longer than 15 characters. This improvescompatibility with all linkers, including BSD systems.

-v0

Silent operation. No output to console other than warning anderror messages.

-v1

Verbose. Output basic information about file names and types (Default).

-v2

More verbose. Tell about conversions and library operations.

-wdXXXDisable warning number XXX.

-weXXX

Treat warning number XXX as an error.

-edXXXDisable error message number XXX.

-ewXXX

Treat error number XXX as warning.

-imagebase=XXX Specify desired image-base as a hexadecimal number. (Only5used if converting incompatible relocation types).
@RFILE

Read additional command line parameters from response file RFILE.

-h

Help. Print list of options.

Command line parameters can be stored in a response file. This can be useful if thecommand line is long and complicated. Just write @ followed by the name of the response
file. The contents of the response file will be inserted at the place of its name.
Response files can be nested, and there can be a maximum of ten response files.
Response files can have multiple lines and can contain comments. A comment starts with #or // and ends with a line break.

3 Warning and error control
Objconv can be called from a make utility. The make process will stop in case of an error
message but not in case of warning messages. It is possible to disable specific error
messages (-edXXX), to convert errors to warnings (-ewXXX) and to convert warnings toerrors (-weXXX).
It is possible to disable error number 2005 is you want the input file and output file to havethe same name. It is possible to disable error number 2505 if you want to mix object files
with different word sizes in the same library.

4 Converting file formats
An object file can be converted from one format to another by specifying the desired format
for the output file. The format of the input file is detected automatically. For example, toconvert the 32-bit COFF file file1.obj to ELF:
objconv -felf32 -nu file1.obj file1.o
The name of the output file will be generated, if it is not specified, by replacing the extensionof the input file with the default extension for the target format. The name of the output file
must be different from the input file.
It is recommended to always use the -nu option. This makes objconv add or remove
leading underscores on symbol names if required.
The output file will always have the same word size as the input file. It is not possible tochange e.g. from 32-bit to 64-bit format.
A library is converted in the same way as an object file:
objconv -felf32 -nu file1.lib file1.a
Debug information and exception handling information is removed from the file, by default, if
the format of the output file is different from the input file. It is recommended to remove thisinformation because it will be incompatible with the target system. Objconv does not include
a facility for converting this information to make it compatible.
6Further instructions on converting assembler-generated and compiler-generated object
code are given below in chapter 9 and 10.

5 Modifying symbols
It is possible to modify the names of public and external symbols in object files and libraries
in order to prevent name clashes, to fix problems with different name mangling systems,
etc.
Note that symbol names must be specified in the way they are represented in object files,
possibly including underscores and name mangling information. All names are treated ascase sensitive. Use the dump or disassembly feature to see the mangled symbol names.
To change the symbol name name1 to name2 in object file file1.obj:
objconv -nr:name1:name2 file1.obj file2.obj
The modified object file will be file2.obj. Objconv will replace name1 with name2
wherever it occurs in public, external and local symbols, as well as section names andlibrary member names. All names are case sensitive.
It is possible to give a function more than one name. This can be useful for supporting
multiple naming conventions with the same object or library file. Only public (exported)
symbol names can have aliases. It is not possible to assign an alias to an external(imported) or local symbol. To give the function named function1 the alias function2:
objconv -ar:function1:function2 file1.obj file2.obj
Some file formats have symbol names prefixed by an underscore ( _ ) while other fileformats have no prefix on symbol names. Use option -nu to change the prefix to thedefault for the target file format when converting from one format to another:objconv -felf -nu file1.obj file2.o
Use option -nu- or -nu+ to explicitly add or remove underscores on all symbol names.
You can specify any prefix to change or remove. For example, to remove prefix _Win_ fromall function names beginning with _Win_:
objconv -np:_Win_: file1.obj file2.obj
Likewise, you can modify all function names with a certain suffix. For example, to remove
suffixes @4, @8 and @12 from all function names:
objconv -ns:@4: -ns:@8: -ns:@12: file1.obj file2.obj
You can keep the old names as aliases when modifying the prefix or suffix of function
names. For example, to make a callable alias for Intel CPU-specific functions with suffix .R:
objconv -as:.R:_AVX: file1.obj file2.obj
No more than one operation can be specified for the same symbol name. For example, you
cannot remove an underscore from a name and make an alias at the same time. You haveto run objconv twice to so. For example, to convert COFF file file1.obj to ELF, remove
underscores, and make an alias:
7

objconv -felf32 -nu file1.obj file1.oobjconv -na:function1:function2 file1.o file2.oLikewise, you have to run objconv twice to make two aliases to the same symbol.
It is possible to make a public symbol weak in ELF and Mach-O files. A weak symbol has
lower priority so that it will not be used if another public symbol with the same name isdefined elsewhere. This can be useful for preventing name clashes if there is a risk that thesame function is supplied in more than one library. Note that only the ELF and Mach-O fileformats supports this feature. To make public symbol function1 weak in ELF file
file1.o:objconv -nw:function1 file1.o file2.o
COFF and OMF files have a different feature called weak external symbols. This is notsupported by objconv.
Objconv can hide public symbols by making them local. A public symbol can be made local
if you want to prevent name clashes or make sure that the symbol is never accessed by anyother module. To hide symbol DontUseMe in COFF file file1.obj:
objconv -nl:DontUseMe file1.obj file2.obj
It is also possible to hide external symbols. This can be used for preventing link errors withunresolved externals. The hidden external symbol will not be relocated. Note that it isdangerous to hide an external symbol unless you are certain that the symbol is never used.
Any attempt to access the hidden symbol from a function in the same module will result in aserious runtime error.
All symbol modification options can be applied to libraries as well as to object files.

6 Managing libraries
A function library (archive) is a collection of object files. Each member (object file) in thelibrary has a name which, by default, is the same as the name of the original object file.
All libraries contain a symbol index in order to make it easier for linkers to find out which
member contains a particular function. Objconv will always remake the symbol index andremove the path from member filenames whenever a library file is modified.
Objconv can add, remove, replace, extract, modify or dump library members.

Rebuilding a library
Rebuilding a library will remove any path from member names, change the member nameextension to .obj for COFF and OMF files, or .o for ELF and Mach-O files, and rebuild thesymbol table. Example rebuilding library mylib.lib:
objconv mylib.lib mylib2.lib

Converting a library
To convert library mylib.lib from COFF to ELF format:
8

objconv -felf mylib.lib mylib.a

Building a library or adding members to a library
To add ELF object files file1.o and file2.o to library mylib.a:objconv -la:file1.o -la:file2.o mylib.aor alternatively:
objconv -lib mylib.a file1.o file2.o
The alternative -lib syntax is intended for make utilities that produce a list of object files
separated by spaces. The library mylib.a will be created if it doesn't exist.
If you want to preserve the original library without the additions then give the new library adifferent name:objconv -la:file1.o -la:file2.o mylib.a mylib2.a
Any members of the old library with the same names as the added object files will be
replaced. Members with different names will be preserved in the library.
Any specified options for format conversion or symbol modification will be applied to theadded members, but not to the old members of the library.

Removing members from a library
To delete member file1.o from library mylib.a:objconv -ld:file1.o mylib.a mylib2.a

Extracting members from a library
To extract object file file1.o from library mylib.a:objconv -lx:file1.o mylib.a
Any path of the original filename is ignored or removed by objconv. To extract library
member C:\some\very\long\path\file1.obj from library mylib.lib and store it as
mypath\file1.obj:
objconv -lx:file1.obj:mypath/file1.obj mylib.lib
You may use | instead of : as separator if the output path contains a colon:
objconv -lx|file1.obj|C:/mypath/file1.obj mylib.lib
To extract all object files from library mylib.lib:
objconv -lx mylib.lib
Any specified options for format conversion or symbol modification will be applied to theextracted members, but the library itself will be unchanged.

9No more than one option can be specified for each library member. For example, you can't
extract and delete the same member in one operation.

Modifying library members
To rename library member file1.o to file2.o in library mylib.a:objconv -nr:file1.o:file2.o mylib.a mylib2.a
To rename symbol function1 to function2 in library mylib.a:objconv -nr:function1:function2 mylib.a mylib2.a
Any symbol modification option specified will be applied to all library members that have asymbol with the specified name.

Dumping library contents
To show all members and their public symbol names in library mylib.a:objconv -d mylib.a
Note that the member names shown are the names before conversion. All other commands
use the member names after any path has been removed. See section 11.16 for how to list
the contents of multiple libraries.
To show the complete symbol list of member file1.o in library mylib.a:objconv -dhs -lx:file1.o mylib.a
To show all symbols in all members of library mylib.a:objconv -dhs -lx mylib.a

7 Dumping files
Objconv can dump file headers, symbol tables, etc. for various types of files. For example,
to dump the file header, section headers and symbol table of file1.obj:
objconv -dfhs file1.obj

8 Disassembling files
Objconv can disassemble object files, executable files, etc. For example, to disassemble thedynamic link library file1.dll to NASM syntax:
objconv -fnasm file1.dll file1.asm
To disassemble a static library file (*.lib, *.a) you must first extract the individual library
members and then disassemble each member separately.
Three different syntax dialects are supported:101. MASM/TASM. Used by Microsoft and Borland assemblers. This is the most common
syntax used in manuals etc. Windows compilers can generate output in this format.
Command line option -fasm or -fmasm or -ftasm.
2. GAS. Used by the Gnu compiler and assembler. Only the Intel syntax sub-version is
supported. Use this for inline assembly with the gcc or g++ compiler. Command line
option -fgasm.
3. NASM/YASM. Used by NASM and YASM. These are free assemblers with support
for multiple platforms. This syntax is more logical and consistent than the otherdialects, but with fewer options. Command line option -fnasm or -fyasm.
The output file is written in such a way that it can be assembled again with the appropriate
assembler. Possible problems with re-assembling the file are discussed below.
The disassembler supports the full instruction set for all 16-, 32- and 64-bit x86 Intel, AMD
and VIA processors, including the Intel SSE, AVX, AVX2, AVX512F/VL/BW/DQ/CD/IFMA/VBMI2/FP16, FMA3, BMI1, BMI2, etc., AMD XOP, FMA4 and TBM instructions, VIA
instructions, privileged instructions, the Intel Knights Corner instruction set, known
undocumented instructions, and preliminary instruction codes that were never implemented
because of changed plans (e.g. SSE5), totaling more than 2000 instructions.
The quality of the disassembly depends on the amount of information contained in the input
file. Object files generally contain more information about symbol names, types, etc. than
executable files do. COFF and ELF files contain more symbol names than OMF and MachO files do.
The disassembler analyzes the code in order to determine the type of each data item, toguess where each function begins and ends, to identify import tables, switch/case jump
tables, virtual function tables, etc. Nevertheless, the disassembler may in difficult cases
misinterpret data as code or fail to determine the type of a data item. When thedisassembler is in doubt whether something is code or data, it will show it as both.
In simple cases, the quality of the disassembly may be good enough for making
modifications in an object file or for extracting a single function from a dynamic link library.
The disassembly of an executable file is unlikely to be good enough for remaking a fully
working executable, but it may be good enough for identifying problems in the code.

8.1 How to interpret the disassembly
The following example shows what a piece of disassembled code may look like (32-bit
Windows, MASM syntax):_text

SEGMENT PARA PUBLIC 'CODE'; section number 1?testb@@YAHH@Z PROC NEAR
moveax, dword ptr [esp + 04H]
; Note: Memory operand is misaligned
movecx, dword ptr [?alpha@@3HA]
add
ecx, eax
push
ecx
call
?testa@@YAHH@Z
add
esp, 4mov
ecx, offset ?list1@@3PAHA; Filling space: 06H; Filler type: lea with same source and destination;
db 8DH, 9BH, 00H, 00H, 00H, 00H
ALIGN
8?_001: add
eax, dword ptr [ecx]addecx, 4cmp
ecx, offset ?list1@@3PAHA + 00001000H
jl
?_001
ret

11

; 0000 _ 8B. 44 24, 04; 0004 _ 8B. 0D, 00000000(d); 000A _ 03. C8; 000C _ 51
; 000D _ E8, 00000000(rel); 0012 _ 83. C4, 04; 0015 _ B9, 00000000(d); 0020 _ 03. 01; 0022 _ 83. C1, 04; 0025 _ 81. F9, 00001000(d); 002B _ 7C, F3; 002D _ C3

?testb@@YAHH@Z ENDP
_text
ENDS

This code can be interpreted as follows:
The name ?testb@@YAHH@Z is the name of the function int testb(int x) as it ismangled by the Microsoft C++ compiler. The disassembler does not translate manglednames to C++ names for you. The MASM assembler allows the characters ? @ $ _ insymbol names.
Line 0000 is the first instruction of the function testb. It reads the parameter x from thestack into register eax. Line 0004 reads a value from a variable in the data segment into
ecx. The name ?alpha@@3HA is a mangled name for int alpha. The note indicatesthat alpha is not optimally aligned. Such notes always apply to the instruction that follows.
Line 000A adds the value of x in eax to the value of alpha in ecx. Line 000C pushes thisvalue on the stack as a parameter to the following function call. Line 000D is a call tofunction int testa(int) with a mangled name. The return value is in eax. Line 0012
cleans up the stack after the function call. Line 0015 loads the address of ?list1@@3PAHA
into ecx. This is the mangled name of an array int list1[].
Next comes a multi-byte nop for aligning the subsequent loop entry. The compiler has used
lea ebx,[ebx+00000000H] instead of 6 nop instructions for filling 6 bytes. The
disassembler has written the exact byte sequence as a comment. This may be
uncommented to recover exactly the same code, but in general it is preferred to use thealign directive instead. The disassembler cannot know whether the desired alignment is 8
or 16 if there are less than 8 bytes up to the next 16-bytes boundary.
Line 0020 is a loop entry with the label ?_001. The input file does not indicate a name forthis label. Therefore the disassembler has assigned the arbitrary name ?_001. Subsequent
nameless code and data labels will be named ?_002, etc.
The first line in the loop reads an integer from the address that ecx points to, i.e. an
element from array list1, and adds it to eax. Line 0022 adds 4, which is the size of eacharray element, to ecx in order to make it point to the next array element.
Line 0025 compares ecx with the address of the end of the array. Line 002B reads theflags from the preceding cmp instruction and jumps back to the top of the loop if the end of
the array has not been reached. Line 002D returns from function testb. The return value isin eax.
This code could be translated back to C++:
int testa(int x);
int list1[1024];
int alpha;
int testb(int x) {int y = testa(x + alpha);for (int i=0; i<1024; i++) y += list1[i];return y;}

The comments to the right of the disassembly code are interpreted as follows. The four
digits after the semicolon is the hexadecimal address of the instruction. This is actually a 32bit value, but in this case the disassembler has saved some space by using only 4hexadecimal digits. It will show 8 hexadecimal digits if necessary, but not more. Addresses
higher than 232 will be shown only as the least significant 8 hexadecimal digits.
12

After the underscore comes the instruction code as hexadecimal bytes. The delimiters : . ,separate the different parts of the instruction code.
The text in parenthesis after the binary code indicates various types of cross-references,using the following abbreviations:
Abbreviationdrelimgrelsegrelrefpoint
indirect
seg
sseg
far
GOT
GOT r
PLT r

Cross reference type
Direct address. The absolute virtual address of target is inserted
Self-relative address
Image-relative address
Address is relative to a segment or group
Address is relative to an arbitrary reference point
To Gnu indirect function dispatcher
A segment address or segment descriptor
Only the segment part of a far target address is inserted
Offset and segment of a far target address
Global offset table entry
Self-relative address of global offset table entry
Self-relative address of procedure linkage table entry

The information about cross-reference types is usually obtained from relocation tables in the
input file. The disassembler will attempt to reconstruct missing cross-reference information,
if possible, in the case of executable files without relocation tables.

8.2 Compatibility problems
Even though the goal has been to make the disassembly output fully compatible with thespecified assembler, there are still some possible compatibility problems. The following
types of problems may occur when re-assembling disassembled code:•

Unsupported relocation types. The original file may contain relocation types notsupported by the assembler. Image-relative relocations are supported only by
MASM. Relocations relative to an arbitrary reference point are supported only by theMacintosh version of the Gnu assembler (which currently doesn't support the Intelsyntax variant). Relocations to a global offset table (GOT), procedure linkage table(PLT) or other import tables are only partially supported by the disassembler. The
type of relocation is indicated in the comment only, not in the instruction. The GOT,
PLT, import tables, etc. are shown as data if contained in the input file.

•

Nonstandard segment names. Most assemblers have little or no support for code
segments with nonstandard names.

•

Nonstandard segment attributes. Most assemblers have little or no support for
specifying segment attributes such as executable, writeable, zerofill, etc.

•

Nonstandard segment alignment. MASM sets the alignment for _text and _data to 16
in 64 bit mode or if .xmm is specified, and 4 if .xmm is not specified. If the defaultalignment does not fit your purpose then append a $-sign and something to thesegment name, e.g. _text$align32 and specify the desired alignment.

•

Special characters in function names. The following special characters are allowed
in identifiers: NASM/YASM: _$@?.~#, Gas: _.$, MASM: _$@?. ('.' only in the
beginning of a name). The disassembler will count names containing illegal
characters and write a notice in the beginning of the file.
13

•

Exception handling information and debugging information. This information isshown only as data. The appropriate directives are not inserted in the code. Use
option -xs to remove exception handling and debugging information.

•

Communal code and data. This will be converted to public when re-assembled. A
comment is inserted in the disassembly file indicating communal code or data.

•

Newer instruction sets. The disassembler supports the newest instruction sets
currently available. The assembler may not support the same instruction sets. The
GAS and NASM assemblers are often the first to support new instruction sets.

•

Executable files. Executable files and dynamic link libraries or shared objects contain
import tables and other information that will not survive a disassembly and reassembly. It may be possible to recover individual functions from an executable file
but not the entire program.

8.3 Using the disassembler for checking machine code
The disassembler does an almost complete syntax check of the code. This can be useful for
debugging purposes and for testing compilers and assemblers during development. For
example, it will write an error message in the output file if there is a memory operand on an
instruction that allows only register operands. Less serious errors, such as redundantprefixes, are written as "Note" rather than "Error".
The disassembler also checks for some cases of suboptimal code, for example unaligned
memory operands, length-changing prefixes, and instructions that could have been coded ina shorter form.
The disassembler does not check for programming errors, such as for example a push that
doesn't have a matching pop.
A note or error message does not necessarily indicate an error in the compiler that built thecode. Compilers may sometimes have good reasons for coding an instruction in an
apparently suboptimal form. Error messages typically occur when the compiler has placed
data in a code segment and the disassembler has failed to identify this as data. Anotherpossible cause of errors is misplaced labels caused by address calculations that thedisassembler has failed to trace correctly. It is very unlikely that the error messages you see
are caused by bugs in the compiler.

8.4 Assembly syntax for AVX-512 and Knights Corner instructions
The disassembler supports the instruction set for the AVX-512 instructions and the
instruction set for now obsolete Intel "Many Integrated Core" (MIC) coprocessor codenamed
Knight's Corner. See Intel manuals. These two instruction sets are very similar, but havedifferent optional instruction attributes. Instructions from these two instruction sets differ by asingle bit in the prefix, even for otherwise identical instructions.
These instruction sets extend the size of vector registers to 512 bits. The number of vector
registers is extended to 32 vector registers named zmm0 - zmm31 in 64-bit mode. Only
zmm0 - zmm7 are available in 32-bit mode. The new instructions have many new attributes
for masked operations, broadcast, rounding mode, suppression of exceptions, typeconversion, permutation, and cache eviction hint. The syntax described below is used in thedisassembler.
512 bit memory operand size specifier: MASM and GAS syntax: zmmword, NASM syntax:
zword.
14

Masked operation: {kn}, where kn = k1, k2, ... k7 is the mask register. This attribute is
written after the destination operand. This may be omitted for {k0}. The disassembler
writes {k0} explicitly only if the k0 register is modified by the instruction. A mask register
used for other purposes is written like a normal operand without curly brackets.
Broadcast for memory operand: {1to8} etc. Written after the memory source operand.
Rounding mode: {rn} etc. Written after a comma after the last SIMD operand.
Suppress all floating point exceptions: {sae}. Written after a comma after the last SIMD
operand.
Rounding mode and sae may optionally be combined: {rn-sae}.
The AVX-512 and Knights Corner instructions apply a multiplier to the address offset ofmemory operands with a pointer register and a one-byte offset. This multiplier is usually thesame as the actual size of the source operand before any broadcast or conversion or thedestination operand after any conversion, with masks ignored. The disassembler writes thetotal offset as the product of the offset byte and the multiplier to show how the value iscalculated, for example:
vaddps zmm1 {k2}, zmm3, dword [rsi+12H*4H] {1to16}
An assembler should accept the total offset as well (e.g. [rsi+48H]) and use a 32-bit
offset without multiplier in case the specified offset is not divisible by the multiplier.
Attributes available only with AVX-512 instructions:Zeroing: {z} written after the destination register and after the mask specifier.
Attributes available only with Knights Corner instructions:
Cache eviction hint: {eh}. Written after the memory operand.
Type conversion: {uint16} etc. Written after the source or destination memory operand.
Note that the specified operand size applies to the actual size of the converted memory
operand with masks ignored.
Broadcast for register operand: {aaaa} etc. Written after the register source operand.
Permutation (swizzle): {cdab} etc. Written after the register source operand.
An extra comma is inserted only between the last operand, and attributes that do not apply
to a specific operand, i.e. rounding mode and suppress-all-exceptions.
Multiple attributes on the same operand are written in separate curly brackets, for example:
vaddpd zmm30 {k3}{z}, zmm10, zmm8

; AVX512 instruction

vmovdqa32 yword [rdi] {k1} {sint16} {eh}, zmm2 ; KNC instr.
Rounding mode and suppress-all-exceptions may be considered separate attributes written
in separate curly brackets, or one combined attribute. For example:
orvaddpszmm10 {k4}, zmm20, zmm30, {rn} {sae}vaddpszmm10 {k4}, zmm20, zmm30, {rn-sae}
15

The disassembler currently uses the combined syntax.

9 Converting assembler-generated files
Objconv makes it possible to develop multi-platform function libraries from a single
development platform. The code can be compiled or assembled on one platform and theresulting object or library files can then be converted to different file formats for different
platforms.
It is preferred to make static libraries (*.lib, *.a) rather than dynamic link libraries orshared objects (*.dll, *.so). Shared objects in Unix systems require positionindependent code that can cause compatibility problems.
It is recommended to use assembly code rather than C or C++ in order to avoid any
platform-specific or compiler-specific constructs. Things that can go wrong when converting
compiler-generated code are summarized on page 18 below.
The differences in calling conventions etc. are described in detail in my manual 5: "Calling
conventions for different C++ compilers and operating systems". www.agner.org/optimize.
My manual 2: "Optimizing subroutines in assembly language" explains how to make function
libraries that are compatible with multiple platforms. (www.agner.org/optimize).

32-bit code
The calling conventions and register usage conventions are the same on all 32-bit x86
platforms. This makes it easy to use the same code on different platforms. Differences thathave to be dealt with are:•Underscore prefixes. Function names and variable names get an underscore prefixin 32-bit COFF, OMF, and MachO files, but not in ELF. Objconv will automatically
add or remove underscores, as required, with the -nu option.

•

Function calling convention. The most common calling convention in 32-bit mode is__cdecl. Windows DLL's also use __stdcall. Some Windows compilers use__thiscall for class member functions. You can override the default __thiscall by
specifying __cdecl in the definition of class member functions. Use __cdecl
everywhere to prevent incompatibilities.

•

Virtual functions, constructors, destructors, dynamic memory allocation, runtime typeidentification, structured exception handling, thread-local storage and otheradvanced C++ constructs should be avoided or tested thoroughly before you rely on
it in converted code.

•

Name mangling. Different compilers use different name mangling schemes forfunction names. This problem is usually dealt with by declaring all functions andshared global variables extern "C". For example:
extern "C" int function1(int x);
extern "C" {int globalvariable1 = 0;}Class member functions, overloaded functions and operators cannot be declared
extern "C". The mangled function names must be converted manually with theobjconv -nr or -ar option. Alternatively, you may provide multiple mangled16names for the same function in the assembly code:
name1 proc nearname2 label nearname3 label nearpublic name1, name2, name3; function bodyret
name1 endp
Another way to avoid name mangling is to define a mangled function that is replaced
inline by a call to an unmangled function. See my manual 2: "Optimizing subroutines
in assembly language" for examples. The different name mangling schemes aredescribed in my manual 5 on calling conventions.

64-bit code
In 64-bit code we must take the same considerations as for 32-bit code. Function names
have an underscore prefix only in 64-bit MachO files, not in COFF and ELF. However, there
are several other issues to take care of when converting 64-bit code.
The calling conventions and register usage conventions in 64-bit Windows are different fromthe conventions in 64-bit Unix systems. You can support both sets of conventions bymaking functions with multiple entries in the assembly code. For example:; C function prototype:; extern "C" int Examplefunction (int a, double b);; Assembly:
Unix_Examplefunction proc
; Unix entry
movecx, edi; Unix: a=edi, Windows: a=ecx
movapd xmm1,xmm0; Unix: b=xmm0, Windows: b=xmm1
Win_Examplefunction label near ; Windows entry; function body (a=ecx, b=xmm1)
ret
Unix_Examplefunction endp

If we put parameter b before a then both systems will have b in xmm0, while a will be in edi
and edx, respectively:; C function prototype:; extern "C" int Examplefunction (double b, int a);; Assembly:
Unix_Examplefunction proc
; Unix entry
movedx, edi; Unix: a=edi, Windows: a=edx
Win_Examplefunction label near ; Windows entry; function body (a=edx, b=xmm0)
ret
Unix_Examplefunction endp

I have chosen to put a Win_ prefix on the Windows function entries and Unix_ on the Unix
function entries. It is easy to make objconv remove the Win_ prefixes for the COFF files andremove the Unix_ prefixes for the ELF and MachO files when converting the object orlibrary file:
objconv -fcof64 -nu -np:Win_::example.lib examplecof.lib
objconv -felf64 -nu -np:Unix_:: example.lib exampleelf.aobjconv -fmac64 -nu -np:Unix_:_: example.lib examplemac.a17

We must take care of the differences in register usage conventions. Registers RAX, RCX,
RDX, R8 - R11 and XMM0 - XMM5 can be used without saving in both systems. Registers
RSI, RDI and XMM6 - XMM15 can be used without saving in Unix, but not in Windows.
Registers RBX, RBP and R12 - R15 must be saved and restored if used in both systems. To
make the code compatible with both systems we must follow the strictest rule, which is the
Windows rule. A function with two entries, as in the example above, must have the Unix
entry before the Windows entry in order to avoid polluting register RSI and RDI with thefunction parameters used by Unix when calling from Windows.
If the function calls any other function which could possibly have the Unix convention, thenwe cannot rely on registers RSI, RDI and XMM6 - XMM15 to be unchanged across the call tothe other function.
Both sets of conventions have the stack aligned by 16 before every CALL instruction. The
Windows convention dictates that 32 bytes of "shadow space" must be allocated on thestack before a function call. This shadow space belongs to the called function. Unix does
not have the shadow space. A function compatible with both sets of conventions should notuse any shadow space, but must allocate a shadow space to any function it calls which
possibly could have the Windows convention.
The Unix convention allows functions to use the "red zone" of 128 bytes above the stack,while Windows does not have a red zone. Avoid using the red zone in multi-platformfunctions.
If the multi-platform function calls another multi-platform function then we can of course relyon the latter function to conform to the strictest convention, but if we are calling a standard
library function, which is available on both platforms, then we must take all of the above
precautions.

10 Converting compiler-generated files
It is always risky to convert compiler-generated object and library files to a different fileformat because the compiler might link to other functions or data that are not available on
the target system. If the source code is available then, by all means, you should prefer torecompile the code on the target platform rather than convert the compiled code. Any
problems you may encounter because of differences in C++ syntax are small compared tothe problems of incompatibilities in the binary interface.
If the source code is not available then you may try to convert the object code. It works in
simple cases, but be prepared for a lot of problems if the function contains incompatible
structures or accesses other incompatible functions or data.
Another possibility is to disassemble the object code, fix all compatibility problems manually,
and then assemble again. This may be the only solution in some cases, but it requires a lotof experience to understand the disassembled code. A disassembly or file dump may also
be helpful for diagnosing conversion problems.
The following table summarizes the main reasons why converted object code may fail.
Reasons why conversion of compiler-generated code may failCompiler-specificlibrary calls

Calls to operating

Most compilers can generate calls to library functions that are specificto that particular compiler or use compiler-specific global variables. It
may be necessary to convert the called functions as well or makereplacements for the missing functions or variables
Operating system calls are not compatible among systems.
18systemCalling conventionsin 32-bit mode

Most compilers support the same calling conventions in 32-bit mode.
You may have to specify a specific calling convention, preferably__cdecl as explained above.
Calling conventions The calling conventions in 64-bit Windows and 64-bit Unix systems are
in 64-bit mode
different. You need a call stub as explained below.
Register usage
The register usage conventions are the same in all 32-bit systems,
conventions in 32-bit except for Watcom compilers.
mode
Register usage
Linux functions may modify registers RSI, RDI and XMM6 - XMM15,
conventions in 64-bit which must be preserved by Windows functions. You need a call stub tomode
fix this incompatibility.
Red zone
64-bit Unix systems allow functions to use a "red zone" of 128 bytes
above the stack for local storage. Windows does not specify a red zone.
If a converted Unix function uses the red zone under Windows it willusually work. The Windows system will switch stacks in case of aninterrupt so the red zone is not overwritten, but the system could
possibly discard the red zone if it is low on memory. This could produce
extremely rare and irreproducible errors. No error will happen if the Unix
function is compiled with option -mno-red-zone.
Leading underUse the -nu option on objconv to add or remove leading underscoresscores on names
as needed.
Mangling of function Different compilers use different name mangling schemes. Use extern
names"C" on all function declarations in C++ to avoid name mangling. If thisis not possible then you may have to change the mangled name byusing the -nr option in objconv.
Initialization andInitialization and termination code is used for calling the constructors
termination codeand destructors of global objects and for initializing function libraries,
etc. Objconv attempts to convert the initialization code, but thetermination code is often incompatible and will not work.
Exception handlingThis information is not compatible between different systems. Objconv
and stack unwinding will remove this information by default. Do not rely on structured
exception handling. Do not rely on destructors being called at longjmp
informationor when a thread is terminated.
Other advanced
Virtual functions, constructors, destructors, dynamic memory allocation,
C++ constructs
runtime type identification, thread-local storage, member pointers andother advanced C++ constructs may not work after conversion.
Communal functions Objconv does not include a feature for converting communal(coalesced) data. Do not rely on function-level linking (/Gy) on
and data
Microsoft compilers or -ffunction-sections on Gnu compilers.
Communal functions will be converted to non-communal in some cases.
Conversion of communal functions in OMF files is not supported.
Incompatible
Mach-O files allow a relocation type that computes addresses relative torelocation types
an arbitrary reference point. This is not supported by other systems. 64bit COFF files may contain image-relative relocations not supported in
ELF. 64-bit ELF files may contain 32-bit absolute addresses notsupported in Mach-O. Objconv may be able to work around some ofthese problems if a specific image base is specified.
PositionUnix systems require position-independent code when making shared
independent code
objects (*.so). Windows compilers are not able to make positionindependent code. Use static linking when using converted object files
on these systems. Avoid conversion of compiler-generated positionindependent code (use g++ option -fno-pic). See my manual"Optimizing subroutines in assembly language" for instructions on how
to make position-independent 32-bit code in assembly.
Lazy binding
Import tables for lazy binding of external references are not compatible
19

Default library
information

between different systems. Objconv will convert lazy to non-lazyreferences in some cases.
Information in object files about which libraries to include is notconverted by objconv because the libraries are unlikely to have thesame names in the target system.

Conversion between different Unix systems is more likely to be successful than conversion
between Unix and Windows.

10.1 Call stubs for 64-bit conversions
It is necessary to use call stubs when converting 64-bit compiler-generated code between
Windows and Linux systems. Call stubs are not needed for 32-bit code or when converting
between different Unix systems.
The purpose of the call stubs is to take care of the differences in calling conventions andregister usage conventions between 64-bit Windows and 64-bit Unix. Several standard callstubs are provided with objconv: w2ustub.o is needed when calling a 64-bit function thathas been converted from Windows to Unix. u2wstub.obj is needed when calling a 64-bit
function that has been converted from Unix to Windows. You can find these files inextras.zip.
The standard stubs w2ustub.o and u2wstub.obj work only when the converted function
satisfies the following conditions:•

The function must have no more than four parameters.

•

The parameters cannot be a composite type (struct, class), but pointers andreferences to such types are allowed. Member pointers are not allowed. Arrays ofany type are allowed.

•

If any parameter is of type float or double then there can be no parameters of
any other type than float and double. long double cannot be used.

•

Parameters of intrinsic vector types (__m128, __m128d, __m128i) require adifferent stub, see below.

•

The function cannot have a variable parameter list, such as printf.

•

The return can be void or any type. If the return is a composite type then this may
use a return pointer, counting as one parameter. Class member functions have an
implicit this pointer, also counting as one parameter.

•

No stub is needed in 32-bit mode. No stub is needed when converting between
Linux, BSD and Mac.

If these conditions are not met, i.e. if the function has more than four parameters or if it hasa mixture of floating point and integer parameters, then you have to make a tailor-made callstub in assembly language. See the source code w2ustub.asm and u2wstub.asm.
The following examples explain how to use the call stubs. Assume that you have a 64-bit
Windows function library containing a function called Alpha that you want to use in a Linuxsystem. For example, Alpha can have the following definition:
extern "C" int Alpha(int a, int b);

20

A dump of the library shows that the function Alpha is in module alpha.obj. We will
extract this from the library:objconv -fcof64 -lx:alpha.obj somelibrary.lib
Now we want to convert alpha.obj to ELF format. At the same time we can change thename of function Alpha to something else, e.g. w_Alpha:objconv -felf64 -nr:Alpha:w_Alpha alpha.obj alpha.o
The reason why we want to change the name is that we want to call the function through acall stub. The main program calls a stub named Alpha, which in turn calls the convertedfunction w_Alpha.
Now we can make the stub from w2ustub.o by inserting the names in this standard stub:objconv -felf -nr:uname:Alpha -nr:wname:w_Alpha w2ustub.o astub.o
We can now build the executable from the main file, the converted object file and the stub. If
the file main.cpp contains the call to Alpha:g++ -m64 main.cpp alpha.o astub.o
We have to check if the converted function calls any other functions. Use the dump featureof objconv and look at the list of external symbols to see if the function needs access toother functions.
If the converted function Alpha contains a call to another Windows function, Beta, then thelatter function must be converted as well. No stub is needed when a converted function
Alpha calls another converted function Beta.
But if the converted Windows function calls a Unix function then this call must go through areverse stub. Assume that the converted Windows function Alpha calls the standard libraryfunction sin. This function is available with the same name in both Windows and Unix
libraries. Rather than converting the Windows math library (which would probably fail), we
prefer to call the sin function in the Unix function library. We have to change the name ofsin in alpha.o in order to avoid calling the Unix function library directly:
objconv -felf -nr:Alpha:w_Alpha -nr:sin:w_sin alpha.obj alpha.o
The reverse stub to call the Unix function sin from Alpha is made from u2wstub.obj:
objconv -felf -nr:uname:sin -nr:wname:w_sin u2wstub.obj sinstub.o
The final executable must include both the forward stub to call Windows function Alphafrom Unix and the reverse stub to call Unix function sin from Alpha:g++ -m64 main.cpp alpha.o astub.o sinstub.oCalling a 64-bit Windows function from BSD goes in exactly the same way. In Mac systems
we need underscore prefixes on the function names _Alpha and _sin:
objconv -fmac -nr:Alpha:w_Alpha -nr:sin:w_sin alpha.obj alpha.oobjconv -fmac -nr:uname:_Alpha -nr:wname:w_Alpha w2ustub.o astub.oobjconv -fmac -nr:uname:_sin -nr:wname:w_sin u2wstub.obj sinstub.o
g++ -m64 main.cpp alpha.o astub.o sinstub.o21

If we want to use a 64-bit Unix function in a Windows program, we can follow an analogous
procedure with the stubs going in the opposite directions.
Assume that we have a 64-bit Linux function Gamma that we want to call from Windows.
Gamma calls the standard library function cos, which is available in our Windows function
library. First we convert the object file gamma.o to COFF format and change the function
names in the file in order to insert call stubs:
objconv -fcof64 -nr:Gamma:u_Gamma -nr:cos:u_cos gamma.o gamma.obj
If the functions Gamma and cos satisfy the conditions for using the standard call stubs, thenwe can insert the names in the stubs:
objconv -fcof -nr:uname:u_Gamma -nr:wname:Gamma u2wstub.obj gstub.obj
objconv -fcof -nr:uname:u_cos -nr:wname:cos w2ustub.o cosstub.obj

Now we can insert the converted object file and the two stubs in the final executable:
cl main.cpp gamma.obj gstub.obj cosstub.obj
Converting from 64-bit MachO to COFF goes the same way, except for the extra
underscores in the conversion:
objconv -fcof64 -nr:_Gamma:u_Gamma -nr:_cos:u_cos gamma.o gamma.obj
Special call stubs for functions with intrinsic vector parameters of type __m128, __m128d
and __m128i are also provided. Use w2ustubvec.o for functions converted from
Windows to Unix with 1 - 4 parameters of these types and no parameters of any other type.
Use u2wstubvec1.obj or u2wstubvec2.obj for functions converted from Unix toWindows with exactly one or two parameters respectively of these types and no parametersof any other type.
More details about incompatibilities between different platforms are documented in mymanual number 5: "Calling conventions for different C++ compilers and operating systems".
(www.agner.org/optimize).

11 Frequently asked questions
11.1 Why is there no graphical user interface?
Most users will prefer to call objconv from a make utility, a script or a batch file. A graphicaluser interface would compromise the cross-platform portability of the source code.

11.2 What kind of files can objconv convert?
Objconv can convert object files (*.obj, *.o) and static library files (*.lib, *.a) for 32-bit and 64bit x86 systems, such as Windows, Linux, BSD and Intel-based Mac OS X.
The conversion is most likely to be successful if the file is built from assembly code withcareful consideration of the calling conventions etc. of the target system. Conversion ofcompiler-generated code works in simple cases where there are no system calls or otherfeatures known to cause problems. Conversion of 64-bit compiler-generated code between
Windows and Unix systems works only if call stubs are inserted.
Se page 18 for a list of reasons why conversions may fail.
22

11.3 Is objconv up to date?
The disassembler is updated to cover more than two thousand instructions, including thelatest AVX512-FP16 instructions.
The object file converter does not cover all object file formats and features. It may fail insome cases.
The library manager does not cover all library formats and features. It may fail in somecases.

11.4 Is it possible to convert files for ARM?
No. A lot of people have asked about this, so there is obviously a need for such a tool, but I
am not going to make it. Objconv supports only files for x86 and x86-64 architectures. It will
require a major rewrite of objconv to make a converter for ARM files. I don't know if othertools such as Gnu objcopy can do the job. If anybody out there has more information on thisthen please let me know so that I can put it into this FAQ.

11.5 Is it possible to convert files for PPC or other architectures?
No. Objconv supports only files for x86 and x86-64 architectures. It will require a major
rewrite of objconv to make a converter for PPC files and there is a little/big endian issue totake care of.

11.6 Is it possible to link converted files into Borland Delphi Pascal?
Yes. The Turbo Delphi compiler accepts object files in 32-bit OMF format, but the object
files must meet several requirements that are poorly documented: (1) The file cannot
contain communal functions (also called function-level linking). Turn off this option in thecompiler (e.g. on bcc32 compiler, use option -VA-). (2) All section names must begin withan underscore, not a dot. You can fix the underscores with objconv -fomf -nu -nd
inputfile.obj outputfile.obj. (3) The object file must contain both _text, _data
and _bss segments. If it doesn't, then add at least one initialized global variable and at least
one uninitialized global variable, and compile again. (4) Delphi does not accept library files.
You must extract the necessary .obj files from the .lib file first. For further information,
see the article "Using C object files in Delphi" at rvelthuis.de/articles/articles-cobjs.html. If
you have problems making this work, then make a DLL and use dynamic linking instead.

11.7 Can I convert an executable file from one system to another?
No. It is not possible to convert executable files between systems because they contain
incompatible system calls. It may be possible to find an emulator that can run theexecutable. For example, the Wine emulator can run Windows executables under Linux if
you are lucky.

11.8 Can I convert from 32 bit code to 64 bit code?
No. The instruction codes are not compatible.

11.9 Can I convert a dynamic link library to another system?
No. Objconv does not support the conversion of dynamic link libraries and shared objects.

2311.10 Can I build a function library that works in all operating systems?
Yes. It is possible to build a static function library that works in all 32-bit or all 64-bit x86
systems. It is preferably coded in assembly language. See the instructions above.

11.11 Why can't I convert an export library?
The export library contains no function code. It contains only references to a DLL.

11.12 Can I convert a static library to a dynamic library?
Yes. You don't need objconv for this. The linker can do this. You only have to add a simple
entry function. The manual for the linker should explain how to do this.

11.13 Can I convert a dynamic library to a static library?
No. If the source code is not available then you will have to disassemble the DLL and
identify the function or functions you need. Then re-assemble this code. This is no easy job,
but it may be possible in simple cases.

11.14 Can I convert a Windows function library to use it under Linux?
It is possible only in simple cases with no system calls. See the instructions above forconverting compiler-generated code.

11.15 Can I convert a Linux function library to use it under Windows?
It is possible only in simple cases with no system calls. See the instructions above forconverting compiler-generated code.

11.16 I want to know which library contains a particular function
You can make a script that lists the contents of multiple libraries. In Windows, make a file
named listall.bat containing this line:
for %%x in ( *.lib ) do objconv -d %%x >> libraries.txt

Make sure objconv.exe is in the path, and run listall.bat in the directory containing
the .lib files.
For Linux, make a script file, for example named listall.sh, containing the lines below,
and make it executable:#!/bin/bash
for x in `ls *.a` ; do ./objconv -d $x >> libraries.txt ; done

These scripts will make a text file listing the functions of each library. Use any text editor or
search tool to search through the libraries.txt file for the function name you arelooking for.

11.17 How do I know if my Linux function uses the red zone?
64-bit Unix systems allow functions to use the red zone. There is no red zone in 32-bit
systems. You can avoid the red zone by compiling with option -mno-red-zone. The
compiler doesn't always use the red zone, even without this option. The only way to find out
if an object file uses the red zone is to inspect a disassembly. This can be quite difficult.
24A converted Linux function that uses the red zone is likely to work in Windows. But there isa theoretical possibility that it will fail with an extremely low frequency. The failure will not be
reproducible and thus difficult to track.

11.18 How do I know if my Linux function has position-independent code
Objconv will issue an error message if you try to convert an object file that contains
addressing modes that are incompatible with the target system. You will see no error
message if objconv is able to work around the problem.

11.19 I have problems porting my Windows application to Linux because theGnu compiler has a more strict syntax. Can I convert the compiled
Windows code instead?
While you are trying to solve a small problem you are creating a much bigger problem
instead. There are so many compatibility problems when converting compiler-generated
code that this method is unlikely to work. Try to use a compiler that supports both operating
systems, such as Gnu, Clang, or Intel.

11.20 Is it possible to extract one or more functions from a binary file orprogram?
It is possible to extract modules from a library file (*.lib, *.a), but it is not possible toautomatically extract a function from an object file, executable file or dynamic link library.
The file may contain spaghetti code that makes it impossible for the objconv program to tellwhere each function begins and ends. You may look at a disassembly to search for thefunction you need. If it is clear where the function begins and ends, and if the function is
independent of other functions and data, then it is possible to isolate this function asassembly code and assemble it again. You have to be an assembly expert to do this.

11.21 Is it possible to convert mangled function names?
It is very tedious to do this manually. As yet there is no tool available for converting manglednames automatically. The Microsoft mangled names contain more information than the Gnu
mangled names do, so it would be preferable to convert from Windows to Linux rather thanvice versa. Se my manual 5: "Calling conventions for different C++ compilers and operating
systems".

11.22 Is it possible to convert function calling conventions automatically?
No conversion is needed when converting between different 32-bit systems, except for classmember functions using the Microsoft __thiscall convention and in rare cases
differences in stack alignment. A conversion is needed when converting 64-bit object files
because Windows and Linux systems use different calling conventions in 64-bit mode. The
standard call stubs supplied with objconv can take care of the most common cases (seepage 20).
It might be possible, at least in principle, to construct a tool that makes a specific call stub
automatically based on the information of function parameter types contained in mangled
function names. This would not work, however, for parameters of composite type because
the mangled function names do not contain enough information to predict how a classobject parameter is transferred. I am not going to build such a tool.

25

11.23 Does the disassembler have an interactive feature?
No. The current version of objconv has no feature for manually telling the disassembler
what is code and what is data, etc. The disassembler does this automatically except in themost difficult cases.

11.24 Is it possible to disassemble an executable file to modify it and thenassemble it again?
The disassembly of an executable program file is unlikely to contain enough information forreconstructing a fully working executable. It may be possible to do this on a DLL in simple
cases, but this would be quite difficult.

11.25 Is it possible to disassemble an object file and fix all compatibility
problems manually?
If you are an expert, yes. Many compatibility problems can be fixed manually. But this is
hard work and there are many pitfalls. This is not for the faint-hearted!

11.26 Is it possible to reconstruct C++ code from a disassembly?
Reconstructing the logic behind a code from the disassembly is a lot of detective work, but it
is possible with very small files. The disassembly of a program file typically contains
hundreds of thousands of code lines. Interpreting so much code is simply an unmanageablejob.

11.27 Why do I get error messages in the disassembly file?
Most disassembly errors occur because the compiler has placed data in the code segment
and the disassembler attempts to interpret these data as code. The disassembler does its
best to distinguish between code and data, but it is not always successful at this.
Another common cause of errors is misplaced labels caused by cross-references withcalculated addresses that the disassembler has interpreted incorrectly.
The disassembler will sometimes show the same binary data both as code and as data if it
is in doubt what it is.
Data in the code segment should be avoided because this leads to inefficient caching andcode prefetching. Unfortunately, some compilers are still putting jump tables etc. in the code
segment. Older compilers do this a lot.

11.28 How does the disassembler distinguish between code and data?
The first assumption is that code segments contain code and data segments contain data.
Unfortunately, some compilers put jump tables and other data into the code segment, eventhough this gives inferior performance. The disassembler follows all cross-references in thecode in order to detect the type of each reference target. If something in the code segment
is referenced as data it will be labeled as data. If an unreferenced sequence in a code
segment begins with several zeroes it will be interpreted as data. If a sequence in a code
segment cannot be disassembled without errors it will be interpreted as data or as dubious.
The disassembler will analyze the code preceding any indirect jump or indirect call in an
attempt to identify various types of jump tables and virtual tables. Absolute, self-relative andimage-relative jump tables are distinguished based on the address-calculating code thatprecedes an indirect jump.
26

The distinction between code and data can fail in the following cases:• If the disassembler has not found any reference to a data object in a code segment• If a data segment contains code
• If there is self-modifying code
• If a piece of code or data is referenced through a calculated pointer, thedisassembler may not be able to completely follow the calculation. This may result ina misplaced label where the disassembler wrongly assumes that the pointer points
to. A misplaced label will lead to misinterpretation of whatever follows the label. Thisis the most common reason for code being interpreted out of phase.

11.29 Can I disassemble byte code?
Objconv cannot convert or disassemble the byte code that is used for .net or Java. Theremay be other tools available for this.

11.30 Can I assemble the output of the disassembler?
Yes, in favorable cases. The output is intended to be fully compatible with the MASM,
TASM, NASM, YASM and Gas assemblers. Select the appropriate syntax dialect on thecommand line. There may be compatibility problems, depending on the assembler. See
page 13 for possible compatibility problems.

11.31 Why does the disassembler not support AT&T syntax?
The AT&T syntax is used for compiler-generated code in the Gnu assembler. This syntax isdifficult to use and confusing because the operands are written in an order that differs fromthe code manuals from Intel and AMD. This becomes increasingly difficult with the newest
instructions that can have up to five operands.
Most versions of the Gnu assembler support the standard Intel syntax, which is easier touse. The Gnu assembler on Macintosh systems may not support Intel syntax. Use anotherassembler instead.
It is important when using the Gnu/Intel syntax to put the directive.intel_syntax noprefix in the beginning of the code. In case of inline assembly for
the Gnu compiler, you must end with .att_syntax prefix in order to enable thecompiler-generated AT&T code that may follow.

11.32 How can I convert assembly syntax?
You can convert an assembly file from one syntax to another by assembling it to an object
file with the appropriate assembler and then disassembling the object file to the desired
syntax with objconv. The names of local labels and other details may be lost in the process.
The Intel C++ compiler for Linux supports inline assembly with both AT&T and MASM
syntax. This may be used for converting MASM or Intel-style instructions to Gas syntax, but
directives etc. are not supported.
An alternative to converting assembly syntax is to assemble with the appropriate assembler
and then converting the resultant object file to the desired file format using objconv.

11.33 Why does my disassembly take so long time?
The handling of symbol tables etc. in objconv is not optimized for very large files. Convertingor disassembling files of megabyte size can sometimes take a long time. The handling of
small to medium size files goes very fast.
27

11.34 How can I save the output of the dump screen to a file?
objconv -dhs myfile > outputfile.txt

11.35 Can you help me with my problems?
No. I am not doing programming work for others. Sorry.

11.36 Are there any alternatives to objconv?
There are certain alternative tools that can convert and manipulate object files.
The Gnu objcopy utility can convert between various object file formats. The objcopy
utility can be recompiled to support the file formats you need.
The Gnu objdump utility can dump and disassemble object files.
Gnu, Clang, and Intel C++ compilers can compile the same source code on both Windows,
Linux, BSD and Mac OS X platforms, although the Windows versions of Gnu and Clangcompilers are not always fully up to date.
The NASM, YASM and JWASM assemblers can assemble the same source code fordifferent object file formats.
The Microsoft linker and library manager can convert from 32-bit OMF to COFF. The
Editbin tool that comes with Microsoft compilers can convert from 32-bit OMF to COFFand modify COFF files.
The Digital Mars compiler includes a tool named COFF2OMF for converting 32-bit COFF files
to OMF.
There are several other disassemblers available of varying quality, some free and somecommercial.
The tdump utility that comes with Borland compilers is useful for dumping COFF and OMF
files, including executable files.

12 Warning and error messages
All possible warning and error messages are listed in the source code in the fileerror.cpp. Below are listed some of the messages that require further explanation.
1050"Position dependent references will not work in .so file".
Shared objects in Linux, BSD and Mac systems require position-independentcode. The code you are converting is position-dependent. It will work if
statically linked into an executable, but not in a shared object.

1051

Weak public not supported in target file type, symbol xxx.
Objconv has changed a public symbol to non-weak. If this symbol clashes
with other symbols having the same name then change its name or hide it.

1061

Symbol xxx has lazy binding.
Objconv attempts to change the external symbol to non-lazy binding. This28

usually works when converting from Mac32.
1054"Cannot find import table".
This warning occurs when disassembling an executable file and thedisassembler lacks support for recognizing the import table in the file type inquestion. Some imported symbol names may be missing or wrong in thedisassembly output.

1300"File contains 32-bit absolute address".
This can occur when converting from 64-bit ELF to Mach-O and the filecontains 32-bit addresses. Linux and BSD allow 32-bit absolute addresses in
64-bit files because they keep all addresses below 231 (the limit of a signed
32-bit addresses). The OS X Darwin system does not allow this because alladdresses are usually above 232. It is possible to work around the problem byspecifying an image base less than 231 to the linker in order to keep
addresses within the 32-bit address space. Objconv must know the value ofthe image base so that it can convert the not-allowed 32-bit absolute address
to a 32-bit image-relative address. You must specify the same image base to
objconv and to the linker. Objconv will use the value 400000 (hexadecimal) if
not specified. The following example shows how to build the executable:
objconv -fmac64 -imagebase=400000 f1elf.o f1mac.o
g++ -m64 -image_base 400000 -pagezero_size 1000 main.cpp f1mac.o

pagezero_size must be ≤ image_base. All numbers are hexadecimal.
1301"Image-relative address converted to absolute".
This can occur when converting from 64-bit COFF to ELF and the filecontains addresses relative to the image base. This addressing mode is notsupported in ELF. Objconv can convert the image-relative address to an
absolute address if it knows the value of the image base. You can specify adesired image base to objconv and specify the same image base to thelinker. For example:
objconv -felf64 -imagebase=400000 file1.obj file1.o
g++ -m64 --image-base 400000 main.cpp file1.o

If your version of the Gnu linker doesn't accept the --image-basecommand then you must find out which image base it uses and set this value
in the objconv command line. The image base must be less than 0x80000000
for the conversion to work. The addresses are all hexadecimal.
2042"Relocation to global offset table found. Cannot convert position-independentcode".
The object file contains position-independent code using a global offset table(GOT). Objconv does not support the conversion of this type of code.

12.1 Linker errors:_atexit or __cxa_atexit unresolved external
The program is registering a destructor to be called after main() has finished.
This is not compatible among systems. You may fix the linker error by making
a dummy function with this name that does nothing, but the destructor will not
be called.
___cxa_guard_acquire __cxa_guard_release unresolved externals
These functions are locks used by the Gnu compiler to make the initializationof local static objects thread-safe. You may Insert dummy functions for these:
extern "C" void __cxa_guard_acquire(){};
extern "C" void __cxa_guard_release(){};

29

__gxx_personality_v0 unresolved external
Make sure that objconv strips exception information (option -xs).
If you get this error on a Unix target system then make sure you compile withg++, not gcc. If you get this error on a Windows target system then make adummy variable with this name:extern "C" int _gxx_personality_v0 = 0;
kernel32.lib missing
This library is needed by Windows command line compilers. You need todownload Microsoft Software Development Kit to get this library. There are
two versions of kernel32.lib. The 32-bit version is in the Lib directory,
the 64-bit version with the same name is in Lib\x64.
The Mac linker says that the table of contents is out of date.
Some versions of the Mac linker (ld) makes an error message if the datestamp of a .a file has been changed. You can fix the problem by runningranlib on the .a file.

13 Source code
The source code can be used for building the objconv executable for a particular platform
and for modifying the program. The code is in C++ language and can be compiled withalmost any modern C++ compiler that supports 64-bit integers on any platform with littleendian memory organization. The code has been tested with Microsoft, Intel, Gnu, andClang compilers. The code cannot run on platforms with big-endian memory organization,such as the PowerPC-based Mac.
You don't need to read the rest of this chapter unless you want to modify the source code ofobjconv.

13.1 Explanation of the objconv source code
The source code is intended to be compatible with all C++ compilers. Any modified codeshould preferably be tested on more than one compiler, including the Gnu compiler which
has the strictest syntax checking.
All dynamic data allocation must use the container classes declared in containers.h inorder to prevent memory leaks. The following container classes are available:
CMemoryBuffer is useful for containing binary data of mixed type. You can append a data
object x of any type to an instance A of CMemoryBuffer with A.Push(&x,sizeof(x)).
You can append a zero-terminated ASCII string s with A.PushString(s). You can reada data object x of type mytype stored in A at offset os with x = A.Get<mytype>(os);or x = *(mytype*)(A.Buf() + os); The former method does not work with oldversions of the Gnu compiler if A is an instance of a template class derived from
CMemoryBuffer, such as CELF<>. Use the type casting method in CELF and its
descendants.
Note that it is dangerous to make a pointer to an object stored in a container because theinternal buffer in the container class instance can be re-allocated when new data are added
to the buffer. In some cases, the source code does use the unsafe technique of storing
pointers to such data, but only when there is certainty that nothing is added to the container
after the pointer has been assigned.
The container class CFileBuffer is derived from CMemoryBuffer. It adds methods forreading and writing files and for detecting the type of a file.
30

CTextFileBuffer, derived from CFileBuffer, is used for ASCII files.
The overloaded operators >> and << are used for transferring ownership of a memory
buffer from one container to another. It works with all descendants of CFileBuffer.
The template classes CArrayBuf<RecordType> and CSList<RecordType> are used
for dynamic arrays where all members have the same type RecordType. Instances ofthese classes can be used as simple arrays with the index operator []. CArrayBuf allows
RecordType to have constructors and destructor, CSList does not. A dynamic array oftype CArrayBuf has a size which cannot be changed after it has been set. A dynamicarray of type CSList can be appended or resized at any time.
CSList is useful for sorted lists. A.PushSort(x) will insert object x in the list A in the rightposition so that the list is kept sorted at all times. A.PushUnique(x) does the same, but
avoids duplicates. The sort criterion is determined by defining the operator < forRecordType.
All conversions of data files are done by a number of converter classes, which are alldescendants of CFileBuffer. A file buffer can convert the data it contains by creating an
object of the appropriate converter class, transferring ownership of its data buffer to theconverter class object, letting the converter class do the conversion, and then taking backownership of the converted data buffer, as shown in this example:
void CConverter::OMF2COF() {// Convert OMF to COFF file
COMF2COF conv;*this >> conv;
conv.ParseFile();if (err.Number()) return;conv.Convert();*this << conv;}// Make object for conversion// Give it my buffer// Parse file buffer// Return if error// Convert// Take back converted buffer

The operators >> and << can transfer ownership of the contained data buffer because theclasses CConverter and COMF2COF are both descendants of CFileBuffer.
The converter class CELF and its descendants are template classes with all the data
structures of 32-bit or 64-bit ELF files as template parameters. This is because of theconsiderable difference between the data structures in 32-bit and 64-bit ELF files. The
templates are instantiated explicitly in the bottom of elf.cpp.
The reading and interpretation of command line parameters is done by the class
CCommandLineInterpreter, which has a single instance cmd. cmd is a global object sothat it can be accessed from all parts of the program without being passed as a parameter.
Another global object is the error handler err, which is an instance of the class
CErrorReporter. All error reporting is done with err.submit(ErrorNumber).
Exceptions are not used, for reasons of performance.
The Gnu compiler version 4 has a problem with inheritance from template classes becauseof an overly strict interpretation of the so-called two phase lookup rule. This problem iscircumvented by putting this-> in front of every access to members of an ancestor classin a class derived from a template class. For example, to access CELF<>::NSections
from CELF2COF<> (which is derived from CELF<>), you have to write this->NSections.
It is recommended to test that the code can be compiled with the Gnu compiler in order tocatch these problems.
3113.2 How to add support for new file formats
Define an id constant FILETYPE_NEWTYPE in maindef.h to identify the new file type. Add
functionality in CFileBuffer::GetFileType() in containers.cpp for detecting thisfile type and its word size (16, 32 or 64 bits). Add a name for this file type to
FileFormatNames[] in containers.cpp.
Define a class CNewType derived from CFileBuffer with member functions for parsing
and dumping files of this type. The class declaration goes into containers.h. The
definition goes into a new .cpp file named after the new type. Define converter classes forconverting to and from the COFF or ELF type analogously to the existing converter classes
in converters.h. Each converter class is derived from the class for the file type you
convert from. Add member functions to CConverter for each converter class. Add casestatements in CConverter::Go() in main.cpp for each possible conversion. A
conversion may go through multiple steps if there is no converter class for direct conversion
between the two types. You may also define a converter class for converting from NewType
to itself in order to make it possible to modify symbol names in a file of type NewType
without converting to one of the base types COFF or ELF and back again.
If the new file type contains x86 or x86-64 code then you may add a converter class fordisassembling the new type. See below for the interface to the disassembler.
Note that the different object file formats differ in the way self-relative references are definedin relocation records. ELF and 32-bit Mach-O files define self-relative references relative tothe beginning of the relocation source field. COFF and OMF files define self-relativereferences relative to the end of the instruction needing the reference, as the x86
processors do. The difference between the two methods is equal to the length of the source
field plus the length of any immediate operand in the instruction. 64-bit Mach-O files use a
mixture of these two methods.
Objconv does not support file types with big endian memory organization.

13.3 How to add features to the disassembler
Only file types based on the x86 instruction set and its many extensions can be handled by
the disassembler in objconv.
To add support for disassembling a new file type, you first have to make a converter class,as explained above. The converter class creates an instance of CDisassembler and uses
the following member functions of CDisassembler: Use CDisassembler::Init for
defining file type and possibly image base. Use CDisassembler::AddSection for
defining each segment or section. Sections are numbered sequentially, starting at 1. Use
CDisassembler::AddSymbol for defining local, public and external symbols. These canbe numbered in random order, but numbers must be positive and limited. Use
CDisassembler::AddRelocation for defining all cross-references and relocatableaddresses. These can refer to symbol numbers. Use CDisassembler::Go to do thedisassembly after all sections, symbols and relocations have been defined. Finally, takeownership of the disassembly file CDisassembler::OutFile.
You can add support for new instruction codes by adding entries to the opcode tables in
opcodes.cpp. The meaning of each field in the opcode table records is defined in the
beginning of disasm.h.

32Modifications to the functionality of the disassembler go into disasm1.cpp. Modifications to
the way the disassembly output looks or support for alternative assembly syntaxes go into
disasm2.cpp.

13.4 File list
Files in objconv.zip
instructions.pdf
objconv.exe
source.zip
extras.zip

This file
Executable for Windows
Complete source code
Call stubs etc.

Files in source.zip
build.shobjconv.vcproj
cmdline.cpp
cof2asm.cpp
cof2cof.cpp
cof2elf.cpp
cof2omf.cpp
coff.cpp
containers.cpp
disasm1.cpp
disasm2.cpp
elf.cpp
elf2asm.cpp
elf2cof.cpp
elf2elf.cpp
elf2mac.cpp
error.cpp
library.cpp
mac2asm.cpp
mac2elf.cpp
mac2mac.cpp
macho.cpp
main.cpp
omf.cppomf2asm.cpp
omf2cof.cpp
omfhash.cpp
opcodes.cpp
stdafx.cpp
cmdline.hcoff.hcontainers.hconverters.hdisasm.helf.herror.hlibrary.hmacho.hmaindef.h
omf.h
stdafx.h

Script for building objconv for Linux, BSD and Mac systems
Project file for Microsoft compiler
Defines class CCommandLineInterpreter for reading command line
Defines class CCOF2ASM for disassembling COFF files
Defines class CCOF2COF for modifying COFF files
Defines class CCOF2ELF for converting from COFF to ELF
Defines class CCOF2OMF for converting from COFF to OMF
Defines class CCOFF for parsing and dumping COFF files
Container classes CMemoryBuffer, CFileBuffer, CTextFileBuffer
Defines part of class CDisassembler for disassembling
Defines part of class CDisassembler for disassembling
Template class CELF for dumping and parsing ELF files
Template class CELF2ASM for disassembling ELF files
Template class CELF2COF for converting from ELF to COFF
Template class CELF2ELF for modifying ELF files
Template class CELF2MAC for converting from ELF to Mach-O
Defines class CErrorReporter and error texts
Defines class CLibrary for building and modifying .lib and .a files
Defines class CMAC2ASM for disassembling Mach-O files
Defines class CMAC2ELF for converting from Mach-O to ELF
Defines class CMAC2MAC for modifying Mach-O files
Defines class CMACHO for parsing and dumping Mach-O files
Classes CMain and CConverter for dispatching command
Defines class COMF for parsing and dumping OMF files
Defines class COMF2ASM for disassembling OMF files
Defines class COMF2COF for converting from OMF to COFF
Defines class COMFHashTable for hash tables in OMF libraries
Tables for complete set of opcodes for disassembler
Needed only for precompiled headersDeclares class CCommandLineInterpreter and various constants
Structures and constants for COFF files
Declares container classes and container class templates
Declares many converter classes derived from CFileBuffer
Declares several structures and classes used by disassembler
Structures and constants for ELF files
Declares class CErrorReporter for error handling
Structures and classes for managing .lib and .a files
Structures and constants for Mach-O files
Type definitions and other main definitions
Structures, classes and constants for OMF files
Includes all the other .h files
33

Files in extras.zip
u2wstub.obj
u2wstubvec1.obj
u2wstubvec2.obj
w2ustub.ow2ustubvec.o
u2wstub.asm
u2wstubvec1.asm
u2wstubvec2.asm
w2ustub.asm
w2ustubvec.asm

Call stub for functions converted from 64-bit ELF or Mach-O to COFF
Same, with 1 vector parameter
Same, with 2 vector parameters
Call stub for functions converted from 64-bit COFF to ELF or Mach-O
Same, with 1 - 4 vector parameters
Source code for u2wstub.obj
Source code for u2wstub.obj
Source code for u2wstub.obj
Source code for w2ustub.o
Source code for w2ustub.o

13.5 Class list
The most important container classes and converter classes in the objconv source code arelisted below.
Container classes
CMemoryBuffer

CFileBuffer

CTextFileBuffer

CArrayBuf<>

CSList<>Declared in: containers.hDefined in: containers.cpp
Inherit from: none
Description: This is the base container class that all file classes,
converter classes and all classes containing data of mixed types arederived from. The size can grow as new data are added.
Declared in: containers.hDefined in: containers.cpp
Inherit from: CMemoryBuffer
Description: This is the container class that all converter classes andother file handling classes are derived from. It adds methods for reading
and writing files and for detecting the input file type.
Declared in: containers.hDefined in: containers.cpp
Inherit from: CFileBuffer
Description: Container class for reading and writing ASCII text files.
Declared in: containers.hDefined in: containers.h
Inherit from: none
Description: Container class template for arrays where all records
have the same type. The record type is defined as a templateparameter. The size cannot be modified after it has been set. The
record type can have constructors and destructor.
Declared in: containers.hDefined in: containers.h
Inherit from: CMemoryBuffer
Description: Container class template for arrays where all records
have the same type. The record type is defined as a templateparameter. The size can grow as new records are added. The list canbe sorted. The record type can not have constructors or destructor.

Classes for converting files, etc.
CMain
Declared in: converters.hDefined in: main.cpp
Inherit from: CFileBuffer
Description: Dispatching input file to CConverter or CLibrary
CConverter
Declared in: converters.h34

CLibrary

COMFHashTable

CCOF

CCOF2ELF

CCOF2OMF

CCOF2ASM

CCOF2COF

COMF

COMF2COF

COMF2ASM

CELF<>

CELF2COF<>

CELF2MAC<>

Defined in: main.cpp
Inherit from: CFileBuffer
Description: Dispatching input file to any of the converter classes
Declared in: library.hDefined in: library.cpp
Inherit from: CFileBuffer
Description: Reading and building library files of any type
Declared in: library.hDefined in: omfhash.cpp
Inherit from: none
Description: Reading and building hash table for OMF libraries
Declared in: converters.hDefined in: coff.cpp
Inherit from: CFileBuffer
Description: Parsing and dumping of COFF and PE files
Declared in: converters.hDefined in: cof2elf.cpp
Inherit from: CCOFF
Description: Conversion from COFF to ELF
Declared in: converters.hDefined in: cof2omf.cpp
Inherit from: CCOFF
Description: Conversion from COFF to OMF
Declared in: converters.hDefined in: cof2asm.cpp
Inherit from: CCOFF
Description: Disassembly of COFF and PE files
Declared in: converters.hDefined in: cof2cof.cpp
Inherit from: CCOFF
Description: Modification of COFF files
Declared in: converters.hDefined in: omf.cpp
Inherit from: CFileBuffer
Description: Parsing and dumping of OMF files
Declared in: converters.hDefined in: omf2cof.cpp
Inherit from: COMF
Description: Conversion from OMF to COFF
Declared in: converters.hDefined in: omf2asm.cpp
Inherit from: COMF
Description: Disassembly of OMF files
Declared in: converters.hDefined in: elf.cpp
Inherit from: CFileBuffer
Description: Parsing and dumping of ELF files. The 32-bit or 64-bit
ELF structures are defined as template parameters.
Declared in: converters.hDefined in: elf2cof.cpp
Inherit from: CELF<>
Description: Conversion from ELF to COFF. The 32-bit or 64-bit ELF
structures are defined as template parameters.
Declared in: converters.hDefined in: elf2mac.cpp
Inherit from: CELF<>
Description: Conversion from ELF to Mach-O. The 32-bit or 64-bit
35

ELF and MAC structures are defined as template parameters.
CELF2ASM<>
Declared in: converters.hDefined in: elf2asm.cpp
Inherit from: CELF<>
Description: Disassembly of ELF files. The 32-bit or 64-bit ELF
structures are defined as template parameters.
CELF2ELF<>
Declared in: converters.hDefined in: elf2elf.cpp
Inherit from: CELF<>
Description: Modifications of ELF files. The 32-bit or 64-bit ELF
structures are defined as template parameters.
CMACHO<>
Declared in: converters.hDefined in: macho.cpp
Inherit from: CFileBuffer
Description: Parsing and dumping of Mach-O files. The 32-bit or 64bit Mach-O structures are defined as template parameters.
CMACUNIV
Declared in: converters.hDefined in: macho.cpp
Inherit from: CFileBuffer
Description: Parsing Mac universal binary files
CMAC2ASM<>
Declared in: converters.hDefined in: mac2asm.cpp
Inherit from: CMACHO
Description: Disassembly of Mach-O files
CMAC2MAC<>
Declared in: converters.hDefined in: mac2mac.cpp
Inherit from: CMACHO
Description: Modifications of Mach-O files and sorting the symbol
table. The structures are defined as template parameters
CMAC2ELF<>
Declared in: converters.hDefined in: mac2elf.cpp
Inherit from: CMACHO
Description: Conversion from Mach-O to ELF. The 32-bit or 64-bit
MAC and ELF structures are defined as template parameters
CDisassembler
Declared in: disasm.hDefined in: disasm1.cpp, disasm2.cpp, opcodes.cpp
Inherit from: none
Description: Disassembling code. Called from CCOF2ASM,
COMF2ASM, CELF2ASM, CMAC2ASM
CSymbolTable
Declared in: disasm.hDefined in: disasm1.cpp
Inherit from: none
Description: Manage symbol table during disassembly.
CErrorReporter
Declared in: error.hDefined in: error.cpp
Inherit from: none
Description: Printing warnings and errors
CCommandLineInterpreter Declared in: cmdline.h
Defined in: cmdline.cpp
Inherit from: none
Description: Interpretation of command line parameters
CResponseFileBuffer
Declared in: converters.hDefined in: cmdline.cpp
Inherit from: CFileBuffer
Description: Contains response file from command line36

14 Legal notice
Objconv is an open source program published under the conditions of the GNU General
Public License v. 3, as defined in www.gnu.org/licenses/. The program is provided without
any warranty or support.
It may in some cases be illegal to modify, convert or disassemble copyright protectedsoftware files without permission from the copyright owner. It is an open question whether it
is legal to modify or convert a copyright protected function library and use it for otherpurposes than presupposed in the license conditions. It is recommended to ask the vendor
for permission before developing and publishing any software that is built with the use of aconverted copyright protected function library.
Copyright law does not generally permit disassembly of copyright protected software for the
purpose of circumventing a copy protection mechanism, for using part of the code in othercontexts, or for extracting the algorithms behind the code.
European, Australian, and US copyright law does, however, under certain conditions permit
reverse engineering of copyright protected software when the purpose is to extract the
information necessary for establishing interoperability with other software, and only to theextent necessary for this purpose. However, I am not a legal expert. The user should seek
legal advice before deciding whether it is legal to use objconv on copyrighted software for a
specific purpose.

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