#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
int /*<<< orphan*/ O_RDONLY;
int /*<<< orphan*/ exit(int);
int open(char *, int /*<<< orphan*/);
int /*<<< orphan*/ perror(char *);
int /*<<< orphan*/ printf(char *, ...);
int read(int, char *, int);
int main(int argc, char *argv[]) {
  char buffer[5] = {0};
  int fd;
  if (argc != 2) {
    printf("Usage: %s <file>\n", argv[0]);
    exit(-1);
  }
  if ((fd = open(argv[1], O_RDONLY)) == -1) {
    do {
      perror("open");
      exit(-1);
    } while (0);
    ;
  }
  if (read(fd, buffer, 4) != 4) {
    do {
      perror("read");
      exit(-1);
    } while (0);
    ;
  }
  buffer[1] = buffer[1] + 1;
  if (*(int *)buffer == 0x64616321) {
    printf("ok\n");
  } else {
  }
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
movl   $0x0,-0x4(%rbp)
mov    %edi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
lea    -0x15(%rbp),%rdi
xor    %esi,%esi
mov    $0x5,%edx
call   1040 <memset@plt>
cmpl   $0x2,-0x8(%rbp)
je     11af <main+0x4f>
mov    -0x10(%rbp),%rax
mov    (%rax),%rsi
lea    0xe62(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
mov    $0xffffffff,%edi
call   1080 <exit@plt>
mov    -0x10(%rbp),%rax
mov    0x8(%rax),%rdi
mov    0x2e2a(%rip),%rax
mov    (%rax),%esi
call   1060 <open@plt>
mov    %eax,-0x1c(%rbp)
cmp    $0xffffffff,%eax
jne    11ec <main+0x8c>
jmp    11d6 <main+0x76>
lea    0xe35(%rip),%rdi
call   1070 <perror@plt>
mov    $0xffffffff,%edi
call   1080 <exit@plt>
mov    -0x1c(%rbp),%edi
lea    -0x15(%rbp),%rsi
mov    $0x4,%edx
call   1050 <read@plt>
cmp    $0x4,%eax
je     1221 <main+0xc1>
jmp    120b <main+0xab>
lea    0xe05(%rip),%rdi
call   1070 <perror@plt>
mov    $0xffffffff,%edi
call   1080 <exit@plt>
movsbl -0x14(%rbp),%eax
add    $0x1,%eax
mov    %al,-0x14(%rbp)
cmpl   $0x64616321,-0x15(%rbp)
jne    124b <main+0xeb>
lea    0xddd(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
jmp    1250 <main+0xf0>
jmp    1250 <main+0xf0>
xor    %eax,%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rax
movb   $0x0,0x4(%rsp)
movl   $0x0,(%rsp)
cmp    $0x2,%edi
jne    11bb <main+0x5b>
mov    0x8(%rsi),%rdi
mov    0x2e6b(%rip),%rax
mov    (%rax),%esi
call   1060 <open@plt>
cmp    $0xffffffff,%eax
je     11d6 <main+0x76>
mov    %rsp,%rsi
mov    %eax,%edi
mov    $0x4,%edx
call   1050 <read@plt>
cmp    $0x4,%eax
jne    11df <main+0x7f>
addb   $0x1,0x1(%rsp)
cmpl   $0x64616321,(%rsp)
jne    11b7 <main+0x57>
lea    0xe6a(%rip),%rdi
call   1030 <puts@plt>
xor    %eax,%eax
pop    %rcx
ret
mov    (%rsi),%rsi
lea    0xe3b(%rip),%rdi
xor    %eax,%eax
call   1040 <printf@plt>
mov    $0xffffffff,%edi
call   1080 <exit@plt>
lea    0xe35(%rip),%rdi
jmp    11e6 <main+0x86>
lea    0xe31(%rip),%rdi
call   1070 <perror@plt>
mov    $0xffffffff,%edi
call   1080 <exit@plt>

LLVM IR (-O0):
@.str = [18 x i8] c"Usage: %s <file>\0A\00"
@O_RDONLY = global i32 0
@.str.1 = [5 x i8] c"open\00"
@.str.2 = [5 x i8] c"read\00"
@.str.3 = [4 x i8] c"ok\0A\00"
define i32 @main(i32 %0, i8** %1) {
%3 = alloca i32
%4 = alloca i32
%5 = alloca i8**
%6 = alloca [5 x i8]
%7 = alloca i32
store i32 0, i32* %3
store i32 %0, i32* %4
store i8** %1, i8*** %5
%8 = bitcast [5 x i8]* %6 to i8*
%9 = load i32, i32* %4
%10 = icmp ne i32 %9, 2
br i1 %10, label %11, label %17
11: ; preds = %2
%12 = load i8**, i8*** %5
%13 = getelementptr inbounds i8*, i8** %12, i64 0
%14 = load i8*, i8** %13
%15 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([18 x i8], [18 x i8]* @.str, i64 0, i64 0), i8* %14)
%16 = call i32 @exit(i32 -1)
unreachable
17: ; preds = %2
%18 = load i8**, i8*** %5
%19 = getelementptr inbounds i8*, i8** %18, i64 1
%20 = load i8*, i8** %19
%21 = load i32, i32* @O_RDONLY
%22 = call i32 @open(i8* %20, i32 %21)
store i32 %22, i32* %7
%23 = icmp eq i32 %22, -1
br i1 %23, label %24, label %29
24: ; preds = %17
br label %25
25: ; preds = %24
%26 = call i32 @perror(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.1, i64 0, i64 0))
%27 = call i32 @exit(i32 -1)
unreachable
28: ; No predecessors!
br label %29
29: ; preds = %28, %17
%30 = load i32, i32* %7
%31 = getelementptr inbounds [5 x i8], [5 x i8]* %6, i64 0, i64 0
%32 = call i32 @read(i32 %30, i8* %31, i32 4)
%33 = icmp ne i32 %32, 4
br i1 %33, label %34, label %39
34: ; preds = %29
br label %35
35: ; preds = %34
%36 = call i32 @perror(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.2, i64 0, i64 0))
%37 = call i32 @exit(i32 -1)
unreachable
38: ; No predecessors!
br label %39
39: ; preds = %38, %29
%40 = getelementptr inbounds [5 x i8], [5 x i8]* %6, i64 0, i64 1
%41 = load i8, i8* %40
%42 = sext i8 %41 to i32
%43 = add nsw i32 %42, 1
%44 = trunc i32 %43 to i8
%45 = getelementptr inbounds [5 x i8], [5 x i8]* %6, i64 0, i64 1
store i8 %44, i8* %45
%46 = getelementptr inbounds [5 x i8], [5 x i8]* %6, i64 0, i64 0
%47 = bitcast i8* %46 to i32*
%48 = load i32, i32* %47
%49 = icmp eq i32 %48, 1684103969
br i1 %49, label %50, label %52
50: ; preds = %39
%51 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.3, i64 0, i64 0))
br label %53
52: ; preds = %39
br label %53
53: ; preds = %52, %50
ret i32 0
}

LLVM IR (-O2):
@.str = [18 x i8] c"Usage: %s <file>\0A\00"
@O_RDONLY = global i32 0
@.str.1 = [5 x i8] c"open\00"
@.str.2 = [5 x i8] c"read\00"
@str = [3 x i8] c"ok\00"
define i32 @main(i32 %0, i8** nocapture %1) {
%3 = alloca [5 x i8]
%4 = getelementptr inbounds [5 x i8], [5 x i8]* %3, i64 0, i64 0
%5 = icmp eq i32 %0, 2
br i1 %5, label %10, label %6
6: ; preds = %2
%7 = load i8*, i8** %1
%8 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([18 x i8], [18 x i8]* @.str, i64 0, i64 0), i8* %7)
%9 = tail call i32 @exit(i32 -1)
unreachable
10: ; preds = %2
%11 = getelementptr inbounds i8*, i8** %1, i64 1
%12 = load i8*, i8** %11
%13 = load i32, i32* @O_RDONLY
%14 = tail call i32 @open(i8* %12, i32 %13)
%15 = icmp eq i32 %14, -1
br i1 %15, label %16, label %19
16: ; preds = %10
%17 = tail call i32 @perror(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.1, i64 0, i64 0))
%18 = tail call i32 @exit(i32 -1)
unreachable
19: ; preds = %10
%20 = call i32 @read(i32 %14, i8* %4, i32 4)
%21 = icmp eq i32 %20, 4
br i1 %21, label %25, label %22
22: ; preds = %19
%23 = tail call i32 @perror(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.2, i64 0, i64 0))
%24 = tail call i32 @exit(i32 -1)
unreachable
25: ; preds = %19
%26 = getelementptr inbounds [5 x i8], [5 x i8]* %3, i64 0, i64 1
%27 = load i8, i8* %26
%28 = add i8 %27, 1
store i8 %28, i8* %26
%29 = bitcast [5 x i8]* %3 to i32*
%30 = load i32, i32* %29
%31 = icmp eq i32 %30, 1684103969
br i1 %31, label %32, label %34
32: ; preds = %25
%33 = tail call i32 @puts(i8* dereferenceable(1) getelementptr inbounds ([3 x i8], [3 x i8]* @str, i64 0, i64 0))
br label %34
34: ; preds = %25, %32
ret i32 0
}