#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_TAP;
int /*<<< orphan*/ 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*/ strcpy(char *, int /*<<< orphan*/);
int /*<<< orphan*/ strncpy(int /*<<< orphan*/, char *, int /*<<< orphan*/);
int netio_tap_open(char *tap_devname) {
  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_TAP | IFF_NO_PI;
  if (*tap_devname)
    strncpy(ifr.ifr_name, tap_devname, IFNAMSIZ);
  if ((err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0) {
    close(fd);
    return err;
  }
  strcpy(tap_devname, ifr.ifr_name);
  return (fd);
}


x86 assembly (clang, -O0):
<netio_tap_open>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x10(%rbp)
mov    0x2e75(%rip),%rax
mov    (%rax),%esi
lea    0xe84(%rip),%rdi
call   1080 <open@plt>
mov    %eax,-0x1c(%rbp)
cmp    $0x0,%eax
jge    1199 <netio_tap_open+0x39>
movl   $0xffffffff,-0x4(%rbp)
jmp    1226 <netio_tap_open+0xc6>
lea    -0x18(%rbp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1050 <memset@plt>
mov    0x2e28(%rip),%rax
mov    (%rax),%eax
mov    0x2dff(%rip),%rcx
or     (%rcx),%eax
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%rax
cmpb   $0x0,(%rax)
je     11e0 <netio_tap_open+0x80>
mov    -0x14(%rbp),%edi
mov    -0x10(%rbp),%rsi
mov    0x2df7(%rip),%rax
mov    (%rax),%edx
call   1030 <strncpy@plt>
mov    -0x1c(%rbp),%edi
mov    0x2dde(%rip),%rax
mov    (%rax),%esi
lea    -0x18(%rbp),%rdx
call   1060 <ioctl@plt>
mov    %eax,-0x20(%rbp)
cmp    $0x0,%eax
jge    1214 <netio_tap_open+0xb4>
mov    -0x1c(%rbp),%edi
call   1070 <close@plt>
mov    -0x20(%rbp),%eax
mov    %eax,-0x4(%rbp)
jmp    1226 <netio_tap_open+0xc6>
mov    -0x10(%rbp),%rdi
mov    -0x14(%rbp),%esi
call   1040 <strcpy@plt>
mov    -0x1c(%rbp),%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<netio_tap_open>:
push   %rbp
push   %r14
push   %rbx
sub    $0x10,%rsp
mov    %rdi,%r14
mov    0x2e76(%rip),%rax
mov    (%rax),%esi
lea    0xe85(%rip),%rdi
call   1080 <open@plt>
test   %eax,%eax
js     11ef <netio_tap_open+0x8f>
mov    %eax,%ebx
lea    0x8(%rsp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1050 <memset@plt>
mov    0x2e3a(%rip),%rax
mov    0x2e13(%rip),%rcx
mov    (%rcx),%ecx
or     (%rax),%ecx
mov    %ecx,0x8(%rsp)
cmpb   $0x0,(%r14)
je     11c8 <netio_tap_open+0x68>
mov    0xc(%rsp),%edi
mov    0x2e12(%rip),%rax
mov    (%rax),%edx
mov    %r14,%rsi
call   1030 <strncpy@plt>
mov    0x2df9(%rip),%rax
mov    (%rax),%esi
lea    0x8(%rsp),%rdx
mov    %ebx,%edi
call   1060 <ioctl@plt>
test   %eax,%eax
js     11f6 <netio_tap_open+0x96>
mov    0xc(%rsp),%esi
mov    %r14,%rdi
call   1040 <strcpy@plt>
jmp    1201 <netio_tap_open+0xa1>
mov    $0xffffffff,%ebx
jmp    1201 <netio_tap_open+0xa1>
mov    %eax,%ebp
mov    %ebx,%edi
call   1070 <close@plt>
mov    %ebp,%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_TAP = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i32 0
@TUNSETIFF = global i32 0
define i32 @netio_tap_open(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 %42
11: ; preds = %1
%12 = call i32 @memset(%struct.ifreq* %4, i32 0, i32 8)
%13 = load i32, i32* @IFF_TAP
%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 = icmp ne i8 %18, 0
br i1 %19, label %20, label %26
20: ; preds = %11
%21 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 1
%22 = load i32, i32* %21
%23 = load i8*, i8** %3
%24 = load i32, i32* @IFNAMSIZ
%25 = call i32 @strncpy(i32 %22, i8* %23, i32 %24)
br label %26
26: ; preds = %20, %11
%27 = load i32, i32* %5
%28 = load i32, i32* @TUNSETIFF
%29 = bitcast %struct.ifreq* %4 to i8*
%30 = call i32 @ioctl(i32 %27, i32 %28, i8* %29)
store i32 %30, i32* %6
%31 = icmp slt i32 %30, 0
br i1 %31, label %32, label %36
32: ; preds = %26
%33 = load i32, i32* %5
%34 = call i32 @close(i32 %33)
%35 = load i32, i32* %6
store i32 %35, i32* %2
br label %42
36: ; preds = %26
%37 = load i8*, i8** %3
%38 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 1
%39 = load i32, i32* %38
%40 = call i32 @strcpy(i8* %37, i32 %39)
%41 = load i32, i32* %5
store i32 %41, i32* %2
br label %42
42: ; preds = %36, %32, %10
%43 = load i32, i32* %2
ret i32 %43
}

LLVM IR (-O2):
%struct.ifreq = type { i32, i32 }
@.str = [13 x i8] c"/dev/net/tun\00"
@O_RDWR = global i32 0
@IFF_TAP = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i32 0
@TUNSETIFF = global i32 0
define i32 @netio_tap_open(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 %30, label %7
7: ; preds = %1
%8 = call i32 @memset(%struct.ifreq* %2, i32 0, i32 8)
%9 = load i32, i32* @IFF_TAP
%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 %20, label %15
15: ; preds = %7
%16 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 1
%17 = load i32, i32* %16
%18 = load i32, i32* @IFNAMSIZ
%19 = call i32 @strncpy(i32 %17, i8* %0, i32 %18)
br label %20
20: ; preds = %15, %7
%21 = load i32, i32* @TUNSETIFF
%22 = call i32 @ioctl(i32 %5, i32 %21, i8* %3)
%23 = icmp slt i32 %22, 0
br i1 %23, label %24, label %26
24: ; preds = %20
%25 = call i32 @close(i32 %5)
br label %30
26: ; preds = %20
%27 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 1
%28 = load i32, i32* %27
%29 = call i32 @strcpy(i8* %0, i32 %28)
br label %30
30: ; preds = %1, %26, %24
%31 = phi i32 [ %22, %24 ], [ %5, %26 ], [ -1, %1 ]
ret i32 %31
}