#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*/ EXIT_FAILURE;
int errno;
int /*<<< orphan*/ exit(int /*<<< orphan*/);
int /*<<< orphan*/ fprintf(int /*<<< orphan*/, char *, int, char *);
char *malloc(scalar_t__);
int /*<<< orphan*/ stderr;
int /*<<< orphan*/ strcat(char *, char const *);
int /*<<< orphan*/ strcpy(char *, char const *);
char *strerror(int);
scalar_t__ strlen(char const *);
char *concat(const char *str1, const char *str2) {
  char *result;
  result = malloc(strlen(str1) + strlen(str2) + 1);
  if (result == NULL) {
    fprintf(stderr, "Err.:%d - malloc() %s\n", errno, strerror(errno));
    exit(EXIT_FAILURE);
  }
  strcpy(result, str1);
  strcat(result, str2);
  return result;
}


x86 assembly (clang, -O0):
<concat>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x8(%rbp),%rdi
call   1040 <strlen@plt>
mov    %rax,-0x20(%rbp)
mov    -0x10(%rbp),%rdi
call   1040 <strlen@plt>
mov    -0x20(%rbp),%rdi
add    %rax,%rdi
add    $0x1,%rdi
call   1060 <malloc@plt>
mov    %rax,-0x18(%rbp)
cmpq   $0x0,-0x18(%rbp)
jne    11fe <concat+0x8e>
mov    0x2e24(%rip),%rax
mov    (%rax),%eax
mov    %eax,-0x28(%rbp)
mov    0x2e10(%rip),%rax
mov    (%rax),%eax
mov    %eax,-0x24(%rbp)
mov    0x2e04(%rip),%rax
mov    (%rax),%edi
call   1090 <strerror@plt>
mov    -0x28(%rbp),%edi
mov    -0x24(%rbp),%edx
mov    %rax,%rcx
lea    0xe15(%rip),%rsi
call   1050 <fprintf@plt>
mov    0x2dd9(%rip),%rax
mov    (%rax),%edi
call   1080 <exit@plt>
mov    -0x18(%rbp),%rdi
mov    -0x8(%rbp),%rsi
call   1030 <strcpy@plt>
mov    -0x18(%rbp),%rdi
mov    -0x10(%rbp),%rsi
call   1070 <strcat@plt>
mov    -0x18(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<concat>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
mov    %rsi,%r14
mov    %rdi,%r15
call   1040 <strlen@plt>
mov    %rax,%rbx
mov    %r14,%rdi
call   1040 <strlen@plt>
lea    (%rbx,%rax,1),%rdi
add    $0x1,%rdi
call   1060 <malloc@plt>
test   %rax,%rax
je     11c6 <concat+0x56>
mov    %rax,%rbx
mov    %rax,%rdi
mov    %r15,%rsi
call   1030 <strcpy@plt>
mov    %rbx,%rdi
mov    %r14,%rsi
call   1070 <strcat@plt>
mov    %rbx,%rax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret
mov    0x2e13(%rip),%rax
mov    (%rax),%ebx
mov    0x2e02(%rip),%rax
mov    (%rax),%ebp
mov    %ebp,%edi
call   1090 <strerror@plt>
lea    0xe1a(%rip),%rsi
mov    %ebx,%edi
mov    %ebp,%edx
mov    %rax,%rcx
call   1050 <fprintf@plt>
mov    0x2dd7(%rip),%rax
mov    (%rax),%edi
call   1080 <exit@plt>

LLVM IR (-O0):
@stderr = global i32 0
@.str = [23 x i8] c"Err.:%d - malloc() %s\0A\00"
@errno = global i32 0
@EXIT_FAILURE = global i32 0
define i8* @concat(i8* %0, i8* %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i8*
store i8* %0, i8** %3
store i8* %1, i8** %4
%6 = load i8*, i8** %3
%7 = call i64 @strlen(i8* %6)
%8 = load i8*, i8** %4
%9 = call i64 @strlen(i8* %8)
%10 = add nsw i64 %7, %9
%11 = add nsw i64 %10, 1
%12 = call i8* @malloc(i64 %11)
store i8* %12, i8** %5
%13 = load i8*, i8** %5
%14 = icmp eq i8* %13, null
br i1 %14, label %15, label %23
15: ; preds = %2
%16 = load i32, i32* @stderr
%17 = load i32, i32* @errno
%18 = load i32, i32* @errno
%19 = call i8* @strerror(i32 %18)
%20 = call i32 @fprintf(i32 %16, i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str, i64 0, i64 0), i32 %17, i8* %19)
%21 = load i32, i32* @EXIT_FAILURE
%22 = call i32 @exit(i32 %21)
unreachable
23: ; preds = %2
%24 = load i8*, i8** %5
%25 = load i8*, i8** %3
%26 = call i32 @strcpy(i8* %24, i8* %25)
%27 = load i8*, i8** %5
%28 = load i8*, i8** %4
%29 = call i32 @strcat(i8* %27, i8* %28)
%30 = load i8*, i8** %5
ret i8* %30
}

LLVM IR (-O2):
@stderr = global i32 0
@.str = [23 x i8] c"Err.:%d - malloc() %s\0A\00"
@errno = global i32 0
@EXIT_FAILURE = global i32 0
define i8* @concat(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 %9, label %16
9: ; preds = %2
%10 = load i32, i32* @stderr
%11 = load i32, i32* @errno
%12 = tail call i8* @strerror(i32 %11)
%13 = tail call i32 @fprintf(i32 %10, i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str, i64 0, i64 0), i32 %11, i8* %12)
%14 = load i32, i32* @EXIT_FAILURE
%15 = tail call i32 @exit(i32 %14)
unreachable
16: ; preds = %2
%17 = tail call i32 @strcpy(i8* %7, i8* %0)
%18 = tail call i32 @strcat(i8* %7, i8* %1)
ret i8* %7
}