#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*/ memcpy(char *, char const *, size_t);
size_t strlen(char const *);
char *strndup(const char *s, size_t n) {
  size_t size;
  char *p;
  if (!s)
    return NULL;
  size = strlen(s);
  if (size > n)
    size = n;
  size++;
  p = malloc(size);
  memcpy(p, s, size);
  p[size - 1] = '\0';
  return p;
}


x86 assembly (clang, -O0):
<strndup>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
cmpq   $0x0,-0x10(%rbp)
jne    1158 <strndup+0x28>
movq   $0x0,-0x8(%rbp)
jmp    11bd <strndup+0x8d>
mov    -0x10(%rbp),%rdi
call   1030 <strlen@plt>
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rax
cmp    -0x18(%rbp),%rax
jbe    117b <strndup+0x4b>
mov    -0x18(%rbp),%rax
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rdi
call   1050 <malloc@plt>
mov    %rax,-0x28(%rbp)
mov    -0x28(%rbp),%rdi
mov    -0x10(%rbp),%rsi
mov    -0x20(%rbp),%rdx
call   1040 <memcpy@plt>
mov    -0x28(%rbp),%rax
mov    -0x20(%rbp),%rcx
sub    $0x1,%rcx
movb   $0x0,(%rax,%rcx,1)
mov    -0x28(%rbp),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<strndup>:
push   %r15
push   %r14
push   %r12
push   %rbx
push   %rax
test   %rdi,%rdi
je     1176 <strndup+0x46>
mov    %rsi,%r15
mov    %rdi,%r14
call   1030 <strlen@plt>
mov    %rax,%rbx
cmp    %r15,%rax
cmova  %r15,%rbx
lea    0x1(%rbx),%r12
mov    %r12,%rdi
call   1050 <malloc@plt>
mov    %rax,%r15
mov    %rax,%rdi
mov    %r14,%rsi
mov    %r12,%rdx
call   1040 <memcpy@plt>
movb   $0x0,(%r15,%rbx,1)
jmp    1179 <strndup+0x49>
xor    %r15d,%r15d
mov    %r15,%rax
add    $0x8,%rsp
pop    %rbx
pop    %r12
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
define i8* @strndup(i8* %0, i64 %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i64
%6 = alloca i64
%7 = alloca i8*
store i8* %0, i8** %4
store i64 %1, i64* %5
%8 = load i8*, i8** %4
%9 = icmp ne i8* %8, null
br i1 %9, label %11, label %10
10: ; preds = %2
store i8* null, i8** %3
br label %33
11: ; preds = %2
%12 = load i8*, i8** %4
%13 = call i64 @strlen(i8* %12)
store i64 %13, i64* %6
%14 = load i64, i64* %6
%15 = load i64, i64* %5
%16 = icmp ugt i64 %14, %15
br i1 %16, label %17, label %19
17: ; preds = %11
%18 = load i64, i64* %5
store i64 %18, i64* %6
br label %19
19: ; preds = %17, %11
%20 = load i64, i64* %6
%21 = add i64 %20, 1
store i64 %21, i64* %6
%22 = load i64, i64* %6
%23 = call i8* @malloc(i64 %22)
store i8* %23, i8** %7
%24 = load i8*, i8** %7
%25 = load i8*, i8** %4
%26 = load i64, i64* %6
%27 = call i32 @memcpy(i8* %24, i8* %25, i64 %26)
%28 = load i8*, i8** %7
%29 = load i64, i64* %6
%30 = sub i64 %29, 1
%31 = getelementptr inbounds i8, i8* %28, i64 %30
store i8 0, i8* %31
%32 = load i8*, i8** %7
store i8* %32, i8** %3
br label %33
33: ; preds = %19, %10
%34 = load i8*, i8** %3
ret i8* %34
}

LLVM IR (-O2):
define i8* @strndup(i8* %0, i64 %1) {
%3 = icmp eq i8* %0, null
br i1 %3, label %12, label %4
4: ; preds = %2
%5 = tail call i64 @strlen(i8* %0)
%6 = icmp ugt i64 %5, %1
%7 = select i1 %6, i64 %1, i64 %5
%8 = add i64 %7, 1
%9 = tail call i8* @malloc(i64 %8)
%10 = tail call i32 @memcpy(i8* %9, i8* %0, i64 %8)
%11 = getelementptr inbounds i8, i8* %9, i64 %7
store i8 0, i8* %11
br label %12
12: ; preds = %2, %4
%13 = phi i8* [ %9, %4 ], [ null, %2 ]
ret i8* %13
}