#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*/ perror(char *);
int /*<<< orphan*/ strcpy(char *, int /*<<< orphan*/);
int /*<<< orphan*/ strncpy(int /*<<< orphan*/, char *, int /*<<< orphan*/);
int tap_alloc(char *dev) {
  struct ifreq ifr;
  int fd, err;
  if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
    perror("could not open /dev/net/tun");
    return -1;
  }
  memset(&ifr, 0, sizeof(ifr));
  ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  if (*dev)
    strncpy(ifr.ifr_name, dev, IFNAMSIZ);
  if ((err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0) {
    perror("could not get tap device");
    close(fd);
    return err;
  }
  strcpy(dev, ifr.ifr_name);
  return fd;
}


x86 assembly (clang, -O0):
<tap_alloc>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x10(%rbp)
mov    0x2e65(%rip),%rax
mov    (%rax),%esi
lea    0xe83(%rip),%rdi
call   1080 <open@plt>
mov    %eax,-0x1c(%rbp)
cmp    $0x0,%eax
jge    11b5 <tap_alloc+0x45>
lea    0xe5c(%rip),%rdi
call   1090 <perror@plt>
movl   $0xffffffff,-0x4(%rbp)
jmp    124e <tap_alloc+0xde>
lea    -0x18(%rbp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1050 <memset@plt>
mov    0x2e0c(%rip),%rax
mov    (%rax),%eax
mov    0x2de3(%rip),%rcx
or     (%rcx),%eax
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%rax
cmpb   $0x0,(%rax)
je     11fc <tap_alloc+0x8c>
mov    -0x14(%rbp),%edi
mov    -0x10(%rbp),%rsi
mov    0x2ddb(%rip),%rax
mov    (%rax),%edx
call   1030 <strncpy@plt>
mov    -0x1c(%rbp),%edi
mov    0x2dc2(%rip),%rax
mov    (%rax),%esi
lea    -0x18(%rbp),%rdx
call   1060 <ioctl@plt>
mov    %eax,-0x20(%rbp)
cmp    $0x0,%eax
jge    123c <tap_alloc+0xcc>
lea    0xdf8(%rip),%rdi
call   1090 <perror@plt>
mov    -0x1c(%rbp),%edi
call   1070 <close@plt>
mov    -0x20(%rbp),%eax
mov    %eax,-0x4(%rbp)
jmp    124e <tap_alloc+0xde>
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):
<tap_alloc>:
push   %rbp
push   %r14
push   %rbx
sub    $0x10,%rsp
mov    %rdi,%r14
mov    0x2e66(%rip),%rax
mov    (%rax),%esi
lea    0xe84(%rip),%rdi
call   1080 <open@plt>
test   %eax,%eax
js     1208 <tap_alloc+0x98>
mov    %eax,%ebx
lea    0x8(%rsp),%rdi
xor    %esi,%esi
mov    $0x8,%edx
call   1050 <memset@plt>
mov    0x2e2a(%rip),%rax
mov    0x2e03(%rip),%rcx
mov    (%rcx),%ecx
or     (%rax),%ecx
mov    %ecx,0x8(%rsp)
cmpb   $0x0,(%r14)
je     11d8 <tap_alloc+0x68>
mov    0xc(%rsp),%edi
mov    0x2e02(%rip),%rax
mov    (%rax),%edx
mov    %r14,%rsi
call   1030 <strncpy@plt>
mov    0x2de9(%rip),%rax
mov    (%rax),%esi
lea    0x8(%rsp),%rdx
mov    %ebx,%edi
call   1060 <ioctl@plt>
test   %eax,%eax
js     121b <tap_alloc+0xab>
mov    0xc(%rsp),%esi
mov    %r14,%rdi
call   1040 <strcpy@plt>
mov    %ebx,%eax
add    $0x10,%rsp
pop    %rbx
pop    %r14
pop    %rbp
ret
lea    0xdf1(%rip),%rdi
call   1090 <perror@plt>
mov    $0xffffffff,%ebx
jmp    11fd <tap_alloc+0x8d>
mov    %eax,%ebp
lea    0xdf8(%rip),%rdi
call   1090 <perror@plt>
mov    %ebx,%edi
call   1070 <close@plt>
mov    %ebp,%ebx
jmp    11fd <tap_alloc+0x8d>

LLVM IR (-O0):
%struct.ifreq = type { i32, i32 }
@.str = [13 x i8] c"/dev/net/tun\00"
@O_RDWR = global i32 0
@.str.1 = [28 x i8] c"could not open /dev/net/tun\00"
@IFF_TAP = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i32 0
@TUNSETIFF = global i32 0
@.str.2 = [25 x i8] c"could not get tap device\00"
define i32 @tap_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 %12
10: ; preds = %1
%11 = call i32 @perror(i8* getelementptr inbounds ([28 x i8], [28 x i8]* @.str.1, i64 0, i64 0))
store i32 -1, i32* %2
br label %44
12: ; preds = %1
%13 = call i32 @memset(%struct.ifreq* %4, i32 0, i32 8)
%14 = load i32, i32* @IFF_TAP
%15 = load i32, i32* @IFF_NO_PI
%16 = or i32 %14, %15
%17 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 0
store i32 %16, i32* %17
%18 = load i8*, i8** %3
%19 = load i8, i8* %18
%20 = icmp ne i8 %19, 0
br i1 %20, label %21, label %27
21: ; preds = %12
%22 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 1
%23 = load i32, i32* %22
%24 = load i8*, i8** %3
%25 = load i32, i32* @IFNAMSIZ
%26 = call i32 @strncpy(i32 %23, i8* %24, i32 %25)
br label %27
27: ; preds = %21, %12
%28 = load i32, i32* %5
%29 = load i32, i32* @TUNSETIFF
%30 = bitcast %struct.ifreq* %4 to i8*
%31 = call i32 @ioctl(i32 %28, i32 %29, i8* %30)
store i32 %31, i32* %6
%32 = icmp slt i32 %31, 0
br i1 %32, label %33, label %38
33: ; preds = %27
%34 = call i32 @perror(i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.2, i64 0, i64 0))
%35 = load i32, i32* %5
%36 = call i32 @close(i32 %35)
%37 = load i32, i32* %6
store i32 %37, i32* %2
br label %44
38: ; preds = %27
%39 = load i8*, i8** %3
%40 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %4, i32 0, i32 1
%41 = load i32, i32* %40
%42 = call i32 @strcpy(i8* %39, i32 %41)
%43 = load i32, i32* %5
store i32 %43, i32* %2
br label %44
44: ; preds = %38, %33, %10
%45 = load i32, i32* %2
ret i32 %45
}

LLVM IR (-O2):
%struct.ifreq = type { i32, i32 }
@.str = [13 x i8] c"/dev/net/tun\00"
@O_RDWR = global i32 0
@.str.1 = [28 x i8] c"could not open /dev/net/tun\00"
@IFF_TAP = global i32 0
@IFF_NO_PI = global i32 0
@IFNAMSIZ = global i32 0
@TUNSETIFF = global i32 0
@.str.2 = [25 x i8] c"could not get tap device\00"
define i32 @tap_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 %7, label %9
7: ; preds = %1
%8 = tail call i32 @perror(i8* getelementptr inbounds ([28 x i8], [28 x i8]* @.str.1, i64 0, i64 0))
br label %33
9: ; preds = %1
%10 = call i32 @memset(%struct.ifreq* %2, i32 0, i32 8)
%11 = load i32, i32* @IFF_TAP
%12 = load i32, i32* @IFF_NO_PI
%13 = or i32 %12, %11
%14 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 0
store i32 %13, i32* %14
%15 = load i8, i8* %0
%16 = icmp eq i8 %15, 0
br i1 %16, label %22, label %17
17: ; preds = %9
%18 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 1
%19 = load i32, i32* %18
%20 = load i32, i32* @IFNAMSIZ
%21 = call i32 @strncpy(i32 %19, i8* %0, i32 %20)
br label %22
22: ; preds = %17, %9
%23 = load i32, i32* @TUNSETIFF
%24 = call i32 @ioctl(i32 %5, i32 %23, i8* %3)
%25 = icmp slt i32 %24, 0
br i1 %25, label %26, label %29
26: ; preds = %22
%27 = call i32 @perror(i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.2, i64 0, i64 0))
%28 = call i32 @close(i32 %5)
br label %33
29: ; preds = %22
%30 = getelementptr inbounds %struct.ifreq, %struct.ifreq* %2, i64 0, i32 1
%31 = load i32, i32* %30
%32 = call i32 @strcpy(i8* %0, i32 %31)
br label %33
33: ; preds = %29, %26, %7
%34 = phi i32 [ -1, %7 ], [ %24, %26 ], [ %5, %29 ]
ret i32 %34
}