#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 */
struct ifreq {
  int ifr_flags;
  int /*<<< orphan*/ ifr_name;
};
typedef int /*<<< orphan*/ ifr;

/* Variables and functions */
int IFF_NO_PI;
int IFF_TUN;
scalar_t__ IFNAMSIZ;
int /*<<< orphan*/ O_RDWR;
int /*<<< orphan*/ TUNSETIFF;
int /*<<< orphan*/ close(int);
int ioctl(int, int /*<<< orphan*/, void *);
int /*<<< orphan*/ memset(struct ifreq *, int /*<<< orphan*/, int);
int open(char *, int /*<<< orphan*/);
int /*<<< orphan*/ strncpy(int /*<<< orphan*/, char *, scalar_t__);
int tun_alloc(char *dev) {
  struct ifreq ifr;
  int fd, err;
  if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
    return -1;
  }
  memset(&ifr, 0, sizeof(ifr));
  ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
  if (*dev != 0) {
    strncpy(ifr.ifr_name, dev, IFNAMSIZ - 1);
  }
  if ((err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0) {
    close(fd);
    return err;
  }
  return fd;
}


x86 assembly (clang, -O0):
<tun_alloc>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x10(%rbp)
mov    0x2e85(%rip),%rax
mov    (%rax),%esi
lea    0xe94(%rip),%rdi
call   1070 <open@plt>
mov    %eax,-0x1c(%rbp)
cmp    $0x0,%eax
jge    1189 <tun_alloc+0x39>
movl   $0xffffffff,-0x4(%rbp)
jmp    1212 <tun_alloc+0xc2>
lea    -0x18(%rbp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1040 <memset@plt>
mov    0x2e28(%rip),%rax
mov    (%rax),%eax
mov    0x2e0f(%rip),%rcx
or     (%rcx),%eax
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%rax
movsbl (%rax),%eax
cmp    $0x0,%eax
je     11d8 <tun_alloc+0x88>
mov    -0x14(%rbp),%edi
mov    -0x10(%rbp),%rsi
mov    0x2e0c(%rip),%rax
mov    (%rax),%rdx
sub    $0x1,%rdx
call   1030 <strncpy@plt>
mov    -0x1c(%rbp),%edi
mov    0x2dee(%rip),%rax
mov    (%rax),%esi
lea    -0x18(%rbp),%rdx
call   1050 <ioctl@plt>
mov    %eax,-0x20(%rbp)
cmp    $0x0,%eax
jge    120c <tun_alloc+0xbc>
mov    -0x1c(%rbp),%edi
call   1060 <close@plt>
mov    -0x20(%rbp),%eax
mov    %eax,-0x4(%rbp)
jmp    1212 <tun_alloc+0xc2>
mov    -0x1c(%rbp),%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<tun_alloc>:
push   %rbp
push   %r14
push   %rbx
sub    $0x10,%rsp
mov    %rdi,%r14
mov    0x2e86(%rip),%rax
mov    (%rax),%esi
lea    0xe95(%rip),%rdi
call   1070 <open@plt>
test   %eax,%eax
js     11e3 <tun_alloc+0x93>
mov    %eax,%ebx
lea    0x8(%rsp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1040 <memset@plt>
mov    0x2e3a(%rip),%rax
mov    0x2e23(%rip),%rcx
mov    (%rcx),%ecx
or     (%rax),%ecx
mov    %ecx,0x8(%rsp)
cmpb   $0x0,(%r14)
je     11bd <tun_alloc+0x6d>
mov    0xc(%rsp),%edi
mov    0x2e2a(%rip),%rax
mov    (%rax),%rdx
add    $0xffffffffffffffff,%rdx
mov    %r14,%rsi
call   1030 <strncpy@plt>
mov    0x2e0c(%rip),%rax
mov    (%rax),%esi
lea    0x8(%rsp),%rdx
mov    %ebx,%edi
call   1050 <ioctl@plt>
test   %eax,%eax
jns    11e8 <tun_alloc+0x98>
mov    %eax,%ebp
mov    %ebx,%edi
call   1060 <close@plt>
mov    %ebp,%ebx
jmp    11e8 <tun_alloc+0x98>
mov    $0xffffffff,%ebx
mov    %ebx,%eax
add    $0x10,%rsp
pop    %rbx
pop    %r14
pop    %rbp
ret

LLVM IR (-O0):
%struct.ifreq = type { i32, i32 }
@.str = [13 x i8] c"/dev/net/tun\00"
@O_RDWR = global i32 0
@IFF_TUN = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i64 0
@TUNSETIFF = global i32 0
define i32 @tun_alloc(i8* %0) {
%2 = alloca i32
%3 = alloca i8*
%4 = alloca %struct.ifreq
%5 = alloca i32
%6 = alloca i32
store i8* %0, i8** %3
%7 = load i32, i32* @O_RDWR
%8 = call i32 @open(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str, i64 0, i64 0), i32 %7)
store i32 %8, i32* %5
%9 = icmp slt i32 %8, 0
br i1 %9, label %10, label %11
10: ; preds = %1
store i32 -1, i32* %2
br label %40
11: ; preds = %1
%12 = call i32 @memset(%struct.ifreq* %4, i32 0, i32 8)
%13 = load i32, i32* @IFF_TUN
%14 = load i32, i32* @IFF_NO_PI
%15 = or i32 %13, %14
%16 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 0
store i32 %15, i32* %16
%17 = load i8*, i8** %3
%18 = load i8, i8* %17
%19 = sext i8 %18 to i32
%20 = icmp ne i32 %19, 0
br i1 %20, label %21, label %28
21: ; preds = %11
%22 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 1
%23 = load i32, i32* %22
%24 = load i8*, i8** %3
%25 = load i64, i64* @IFNAMSIZ
%26 = sub nsw i64 %25, 1
%27 = call i32 @strncpy(i32 %23, i8* %24, i64 %26)
br label %28
28: ; preds = %21, %11
%29 = load i32, i32* %5
%30 = load i32, i32* @TUNSETIFF
%31 = bitcast %struct.ifreq* %4 to i8*
%32 = call i32 @ioctl(i32 %29, i32 %30, i8* %31)
store i32 %32, i32* %6
%33 = icmp slt i32 %32, 0
br i1 %33, label %34, label %38
34: ; preds = %28
%35 = load i32, i32* %5
%36 = call i32 @close(i32 %35)
%37 = load i32, i32* %6
store i32 %37, i32* %2
br label %40
38: ; preds = %28
%39 = load i32, i32* %5
store i32 %39, i32* %2
br label %40
40: ; preds = %38, %34, %10
%41 = load i32, i32* %2
ret i32 %41
}

LLVM IR (-O2):
%struct.ifreq = type { i32, i32 }
@.str = [13 x i8] c"/dev/net/tun\00"
@O_RDWR = global i32 0
@IFF_TUN = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i64 0
@TUNSETIFF = global i32 0
define i32 @tun_alloc(i8* %0) {
%2 = alloca %struct.ifreq
%3 = bitcast %struct.ifreq* %2 to i8*
%4 = load i32, i32* @O_RDWR
%5 = tail call i32 @open(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str, i64 0, i64 0), i32 %4)
%6 = icmp slt i32 %5, 0
br i1 %6, label %27, label %7
7: ; preds = %1
%8 = call i32 @memset(%struct.ifreq* %2, i32 0, i32 8)
%9 = load i32, i32* @IFF_TUN
%10 = load i32, i32* @IFF_NO_PI
%11 = or i32 %10, %9
%12 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 0
store i32 %11, i32* %12
%13 = load i8, i8* %0
%14 = icmp eq i8 %13, 0
br i1 %14, label %21, label %15
15: ; preds = %7
%16 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 1
%17 = load i32, i32* %16
%18 = load i64, i64* @IFNAMSIZ
%19 = add nsw i64 %18, -1
%20 = call i32 @strncpy(i32 %17, i8* %0, i64 %19)
br label %21
21: ; preds = %15, %7
%22 = load i32, i32* @TUNSETIFF
%23 = call i32 @ioctl(i32 %5, i32 %22, i8* %3)
%24 = icmp slt i32 %23, 0
br i1 %24, label %25, label %27
25: ; preds = %21
%26 = call i32 @close(i32 %5)
br label %27
27: ; preds = %21, %1, %25
%28 = phi i32 [ %23, %25 ], [ -1, %1 ], [ %5, %21 ]
ret i32 %28
}