#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);
char *memcpy(char *, char const *, size_t);
size_t strlen(char const *);
char *__strndup(const char *src, size_t n) {
  char *result;
  size_t length = strlen(src);
  if (length > n)
    length = n;
  result = malloc(length + 1);
  if (result == NULL)
    return NULL;
  result[length] = '\0';
  return memcpy(result, src, length);
}


x86 assembly (clang, -O0):
<__strndup>:
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    -0x28(%rbp),%rax
cmp    -0x18(%rbp),%rax
jbe    1163 <__strndup+0x33>
mov    -0x18(%rbp),%rax
mov    %rax,-0x28(%rbp)
mov    -0x28(%rbp),%rdi
add    $0x1,%rdi
call   1050 <malloc@plt>
mov    %rax,-0x20(%rbp)
cmpq   $0x0,-0x20(%rbp)
jne    118c <__strndup+0x5c>
movq   $0x0,-0x8(%rbp)
jmp    11ad <__strndup+0x7d>
mov    -0x20(%rbp),%rax
mov    -0x28(%rbp),%rcx
movb   $0x0,(%rax,%rcx,1)
mov    -0x20(%rbp),%rdi
mov    -0x10(%rbp),%rsi
mov    -0x28(%rbp),%rdx
call   1040 <memcpy@plt>
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<__strndup>:
push   %r15
push   %r14
push   %rbx
mov    %rsi,%r15
mov    %rdi,%r14
call   1030 <strlen@plt>
mov    %rax,%rbx
cmp    %r15,%rax
cmova  %r15,%rbx
lea    0x1(%rbx),%rdi
call   1050 <malloc@plt>
mov    %rax,%r15
test   %rax,%rax
je     116e <__strndup+0x3e>
movb   $0x0,(%r15,%rbx,1)
mov    %r15,%rdi
mov    %r14,%rsi
mov    %rbx,%rdx
call   1040 <memcpy@plt>
mov    %r15,%rax
pop    %rbx
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 i8*
%7 = alloca i64
store i8* %0, i8** %4
store i64 %1, i64* %5
%8 = load i8*, i8** %4
%9 = call i64 @strlen(i8* %8)
store i64 %9, i64* %7
%10 = load i64, i64* %7
%11 = load i64, i64* %5
%12 = icmp ugt i64 %10, %11
br i1 %12, label %13, label %15
13: ; preds = %2
%14 = load i64, i64* %5
store i64 %14, i64* %7
br label %15
15: ; preds = %13, %2
%16 = load i64, i64* %7
%17 = add i64 %16, 1
%18 = call i8* @malloc(i64 %17)
store i8* %18, i8** %6
%19 = load i8*, i8** %6
%20 = icmp eq i8* %19, null
br i1 %20, label %21, label %22
21: ; preds = %15
store i8* null, i8** %3
br label %30
22: ; preds = %15
%23 = load i8*, i8** %6
%24 = load i64, i64* %7
%25 = getelementptr inbounds i8, i8* %23, i64 %24
store i8 0, i8* %25
%26 = load i8*, i8** %6
%27 = load i8*, i8** %4
%28 = load i64, i64* %7
%29 = call i8* @memcpy(i8* %26, i8* %27, i64 %28)
store i8* %29, i8** %3
br label %30
30: ; preds = %22, %21
%31 = load i8*, i8** %3
ret i8* %31
}

LLVM IR (-O2):
define noalias i8* @__strndup(i8* nocapture %0, i64 %1) {
%3 = tail call i64 @strlen(i8* dereferenceable(1) %0)
%4 = icmp ugt i64 %3, %1
%5 = select i1 %4, i64 %1, i64 %3
%6 = add i64 %5, 1
%7 = tail call i8* @malloc(i64 %6)
%8 = icmp eq i8* %7, null
br i1 %8, label %11, label %9
9: ; preds = %2
%10 = getelementptr inbounds i8, i8* %7, i64 %5
store i8 0, i8* %10
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 1 %7, i8* align 1 %0, i64 %5, i1 false)
br label %11
11: ; preds = %2, %9
ret i8* %7
}