#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 */
char *malloc(size_t);
int /*<<< orphan*/ sprintf(char *, char *, char const *, char const *);
size_t strlen(char const *);
char *strdupcat(const char *a, const char *b) {
  char *str;
  size_t la = strlen(a);
  size_t lb = strlen(b);
  str = malloc(la + lb + 1);
  if (!str)
    return NULL;
  sprintf(str, "%s%s", a, b);
  return str;
}


x86 assembly (clang, -O0):
<strdupcat>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
mov    -0x10(%rbp),%rdi
call   1030 <strlen@plt>
mov    %rax,-0x28(%rbp)
mov    -0x18(%rbp),%rdi
call   1030 <strlen@plt>
mov    %rax,-0x30(%rbp)
mov    -0x28(%rbp),%rdi
add    -0x30(%rbp),%rdi
add    $0x1,%rdi
call   1040 <malloc@plt>
mov    %rax,-0x20(%rbp)
cmpq   $0x0,-0x20(%rbp)
jne    1187 <strdupcat+0x57>
movq   $0x0,-0x8(%rbp)
jmp    11a7 <strdupcat+0x77>
mov    -0x20(%rbp),%rdi
mov    -0x10(%rbp),%rdx
mov    -0x18(%rbp),%rcx
lea    0xe66(%rip),%rsi
call   1050 <sprintf@plt>
mov    -0x20(%rbp),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<strdupcat>:
push   %r15
push   %r14
push   %rbx
mov    %rsi,%r14
mov    %rdi,%r15
call   1030 <strlen@plt>
mov    %rax,%rbx
mov    %r14,%rdi
call   1030 <strlen@plt>
lea    (%rbx,%rax,1),%rdi
add    $0x1,%rdi
call   1040 <malloc@plt>
mov    %rax,%rbx
test   %rax,%rax
je     1175 <strdupcat+0x45>
lea    0xe99(%rip),%rsi
mov    %rbx,%rdi
mov    %r15,%rdx
mov    %r14,%rcx
call   1050 <sprintf@plt>
mov    %rbx,%rax
pop    %rbx
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
@.str = [5 x i8] c"%s%s\00"
define i8* @strdupcat(i8* %0, i8* %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i8*
%6 = alloca i8*
%7 = alloca i64
%8 = alloca i64
store i8* %0, i8** %4
store i8* %1, i8** %5
%9 = load i8*, i8** %4
%10 = call i64 @strlen(i8* %9)
store i64 %10, i64* %7
%11 = load i8*, i8** %5
%12 = call i64 @strlen(i8* %11)
store i64 %12, i64* %8
%13 = load i64, i64* %7
%14 = load i64, i64* %8
%15 = add i64 %13, %14
%16 = add i64 %15, 1
%17 = call i8* @malloc(i64 %16)
store i8* %17, i8** %6
%18 = load i8*, i8** %6
%19 = icmp ne i8* %18, null
br i1 %19, label %21, label %20
20: ; preds = %2
store i8* null, i8** %3
br label %27
21: ; preds = %2
%22 = load i8*, i8** %6
%23 = load i8*, i8** %4
%24 = load i8*, i8** %5
%25 = call i32 @sprintf(i8* %22, i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i8* %23, i8* %24)
%26 = load i8*, i8** %6
store i8* %26, i8** %3
br label %27
27: ; preds = %21, %20
%28 = load i8*, i8** %3
ret i8* %28
}

LLVM IR (-O2):
@.str = [5 x i8] c"%s%s\00"
define noalias i8* @strdupcat(i8* %0, i8* %1) {
%3 = tail call i64 @strlen(i8* dereferenceable(1) %0)
%4 = tail call i64 @strlen(i8* dereferenceable(1) %1)
%5 = add i64 %3, 1
%6 = add i64 %5, %4
%7 = tail call i8* @malloc(i64 %6)
%8 = icmp eq i8* %7, null
br i1 %8, label %11, label %9
9: ; preds = %2
%10 = tail call i32 @sprintf(i8* %7, i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i8* %0, i8* %1)
br label %11
11: ; preds = %2, %9
ret i8* %7
}