library/std/src/sys/unix/os.rs

   1 //! Implementation of `std::os` functionality for unix systems
   2
   3 #![allow(unused_imports)] // lots of cfg code here
   4
   5 #[cfg(all(test, target_env = "gnu"))]
   6 mod tests;
   7
   8 use crate::os::unix::prelude::*;
   9
  10 use crate::error::Error as StdError;
  11 use crate::ffi::{CStr, CString, OsStr, OsString};
  12 use crate::fmt;
  13 use crate::io;
  14 use crate::iter;
  15 use crate::marker::PhantomData;
  16 use crate::mem;
  17 use crate::memchr;
  18 use crate::path::{self, PathBuf};
  19 use crate::ptr;
  20 use crate::slice;
  21 use crate::str;
  22 use crate::sys::cvt;
  23 use crate::sys::fd;
  24 use crate::sys_common::mutex::{StaticMutex, StaticMutexGuard};
  25 use crate::sys_common::rwlock::{RWLockReadGuard, StaticRWLock};
  26 use crate::vec;
  27
  28 use libc::{c_char, c_int, c_void};
  29
  30 const TMPBUF_SZ: usize = 128;
  31
  32 cfg_if::cfg_if! {
  33     if #[cfg(target_os = "redox")] {
  34         const PATH_SEPARATOR: u8 = b';';
  35     } else {
  36         const PATH_SEPARATOR: u8 = b':';
  37     }
  38 }
  39
  40 extern "C" {
  41     #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
  42     #[cfg_attr(
  43         any(
  44             target_os = "linux",
  45             target_os = "emscripten",
  46             target_os = "fuchsia",
  47             target_os = "l4re"
  48         ),
  49         link_name = "__errno_location"
  50     )]
  51     #[cfg_attr(
  52         any(
  53             target_os = "netbsd",
  54             target_os = "openbsd",
  55             target_os = "android",
  56             target_os = "redox",
  57             target_env = "newlib"
  58         ),
  59         link_name = "__errno"
  60     )]
  61     #[cfg_attr(any(target_os = "solaris", target_os = "illumos"), link_name = "___errno")]
  62     #[cfg_attr(
  63         any(target_os = "macos", target_os = "ios", target_os = "freebsd"),
  64         link_name = "__error"
  65     )]
  66     #[cfg_attr(target_os = "haiku", link_name = "_errnop")]
  67     fn errno_location() -> *mut c_int;
  68 }
  69
  70 /// Returns the platform-specific value of errno
  71 #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
  72 pub fn errno() -> i32 {
  73     unsafe { (*errno_location()) as i32 }
  74 }
  75
  76 /// Sets the platform-specific value of errno
  77 #[cfg(all(not(target_os = "linux"), not(target_os = "dragonfly"), not(target_os = "vxworks")))] // needed for readdir and syscall!
  78 #[allow(dead_code)] // but not all target cfgs actually end up using it
  79 pub fn set_errno(e: i32) {
  80     unsafe { *errno_location() = e as c_int }
  81 }
  82
  83 #[cfg(target_os = "vxworks")]
  84 pub fn errno() -> i32 {
  85     unsafe { libc::errnoGet() }
  86 }
  87
  88 #[cfg(target_os = "vxworks")]
  89 pub fn set_errno(e: i32) {
  90     unsafe { libc::errnoSet(e as c_int) };
  91 }
  92
  93 #[cfg(target_os = "dragonfly")]
  94 pub fn errno() -> i32 {
  95     extern "C" {
  96         #[thread_local]
  97         static errno: c_int;
  98     }
  99
 100     unsafe { errno as i32 }
 101 }
 102
 103 #[cfg(target_os = "dragonfly")]
 104 pub fn set_errno(e: i32) {
 105     extern "C" {
 106         #[thread_local]
 107         static mut errno: c_int;
 108     }
 109
 110     unsafe {
 111         errno = e;
 112     }
 113 }
 114
 115 /// Gets a detailed string description for the given error number.
 116 pub fn error_string(errno: i32) -> String {
 117     extern "C" {
 118         #[cfg_attr(any(target_os = "linux", target_env = "newlib"), link_name = "__xpg_strerror_r")]
 119         fn strerror_r(errnum: c_int, buf: *mut c_char, buflen: libc::size_t) -> c_int;
 120     }
 121
 122     let mut buf = [0 as c_char; TMPBUF_SZ];
 123
 124     let p = buf.as_mut_ptr();
 125     unsafe {
 126         if strerror_r(errno as c_int, p, buf.len()) < 0 {
 127             panic!("strerror_r failure");
 128         }
 129
 130         let p = p as *const _;
 131         str::from_utf8(CStr::from_ptr(p).to_bytes()).unwrap().to_owned()
 132     }
 133 }
 134
 135 pub fn getcwd() -> io::Result<PathBuf> {
 136     let mut buf = Vec::with_capacity(512);
 137     loop {
 138         unsafe {
 139             let ptr = buf.as_mut_ptr() as *mut libc::c_char;
 140             if !libc::getcwd(ptr, buf.capacity()).is_null() {
 141                 let len = CStr::from_ptr(buf.as_ptr() as *const libc::c_char).to_bytes().len();
 142                 buf.set_len(len);
 143                 buf.shrink_to_fit();
 144                 return Ok(PathBuf::from(OsString::from_vec(buf)));
 145             } else {
 146                 let error = io::Error::last_os_error();
 147                 if error.raw_os_error() != Some(libc::ERANGE) {
 148                     return Err(error);
 149                 }
 150             }
 151
 152             // Trigger the internal buffer resizing logic of `Vec` by requiring
 153             // more space than the current capacity.
 154             let cap = buf.capacity();
 155             buf.set_len(cap);
 156             buf.reserve(1);
 157         }
 158     }
 159 }
 160
 161 pub fn chdir(p: &path::Path) -> io::Result<()> {
 162     let p: &OsStr = p.as_ref();
 163     let p = CString::new(p.as_bytes())?;
 164     unsafe {
 165         match libc::chdir(p.as_ptr()) == (0 as c_int) {
 166             true => Ok(()),
 167             false => Err(io::Error::last_os_error()),
 168         }
 169     }
 170 }
 171
 172 pub struct SplitPaths<'a> {
 173     iter: iter::Map<slice::Split<'a, u8, fn(&u8) -> bool>, fn(&'a [u8]) -> PathBuf>,
 174 }
 175
 176 pub fn split_paths(unparsed: &OsStr) -> SplitPaths<'_> {
 177     fn bytes_to_path(b: &[u8]) -> PathBuf {
 178         PathBuf::from(<OsStr as OsStrExt>::from_bytes(b))
 179     }
 180     fn is_separator(b: &u8) -> bool {
 181         *b == PATH_SEPARATOR
 182     }
 183     let unparsed = unparsed.as_bytes();
 184     SplitPaths {
 185         iter: unparsed
 186             .split(is_separator as fn(&u8) -> bool)
 187             .map(bytes_to_path as fn(&[u8]) -> PathBuf),
 188     }
 189 }
 190
 191 impl<'a> Iterator for SplitPaths<'a> {
 192     type Item = PathBuf;
 193     fn next(&mut self) -> Option<PathBuf> {
 194         self.iter.next()
 195     }
 196     fn size_hint(&self) -> (usize, Option<usize>) {
 197         self.iter.size_hint()
 198     }
 199 }
 200
 201 #[derive(Debug)]
 202 pub struct JoinPathsError;
 203
 204 pub fn join_paths<I, T>(paths: I) -> Result<OsString, JoinPathsError>
 205 where
 206     I: Iterator<Item = T>,
 207     T: AsRef<OsStr>,
 208 {
 209     let mut joined = Vec::new();
 210
 211     for (i, path) in paths.enumerate() {
 212         let path = path.as_ref().as_bytes();
 213         if i > 0 {
 214             joined.push(PATH_SEPARATOR)
 215         }
 216         if path.contains(&PATH_SEPARATOR) {
 217             return Err(JoinPathsError);
 218         }
 219         joined.extend_from_slice(path);
 220     }
 221     Ok(OsStringExt::from_vec(joined))
 222 }
 223
 224 impl fmt::Display for JoinPathsError {
 225     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 226         write!(f, "path segment contains separator `{}`", PATH_SEPARATOR)
 227     }
 228 }
 229
 230 impl StdError for JoinPathsError {
 231     #[allow(deprecated)]
 232     fn description(&self) -> &str {
 233         "failed to join paths"
 234     }
 235 }
 236
 237 #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
 238 pub fn current_exe() -> io::Result<PathBuf> {
 239     unsafe {
 240         let mut mib = [
 241             libc::CTL_KERN as c_int,
 242             libc::KERN_PROC as c_int,
 243             libc::KERN_PROC_PATHNAME as c_int,
 244             -1 as c_int,
 245         ];
 246         let mut sz = 0;
 247         cvt(libc::sysctl(
 248             mib.as_mut_ptr(),
 249             mib.len() as libc::c_uint,
 250             ptr::null_mut(),
 251             &mut sz,
 252             ptr::null_mut(),
 253             0,
 254         ))?;
 255         if sz == 0 {
 256             return Err(io::Error::last_os_error());
 257         }
 258         let mut v: Vec<u8> = Vec::with_capacity(sz);
 259         cvt(libc::sysctl(
 260             mib.as_mut_ptr(),
 261             mib.len() as libc::c_uint,
 262             v.as_mut_ptr() as *mut libc::c_void,
 263             &mut sz,
 264             ptr::null_mut(),
 265             0,
 266         ))?;
 267         if sz == 0 {
 268             return Err(io::Error::last_os_error());
 269         }
 270         v.set_len(sz - 1); // chop off trailing NUL
 271         Ok(PathBuf::from(OsString::from_vec(v)))
 272     }
 273 }
 274
 275 #[cfg(target_os = "netbsd")]
 276 pub fn current_exe() -> io::Result<PathBuf> {
 277     fn sysctl() -> io::Result<PathBuf> {
 278         unsafe {
 279             let mib = [libc::CTL_KERN, libc::KERN_PROC_ARGS, -1, libc::KERN_PROC_PATHNAME];
 280             let mut path_len: usize = 0;
 281             cvt(libc::sysctl(
 282                 mib.as_ptr(),
 283                 mib.len() as libc::c_uint,
 284                 ptr::null_mut(),
 285                 &mut path_len,
 286                 ptr::null(),
 287                 0,
 288             ))?;
 289             if path_len <= 1 {
 290                 return Err(io::Error::new(
 291                     io::ErrorKind::Other,
 292                     "KERN_PROC_PATHNAME sysctl returned zero-length string",
 293                 ));
 294             }
 295             let mut path: Vec<u8> = Vec::with_capacity(path_len);
 296             cvt(libc::sysctl(
 297                 mib.as_ptr(),
 298                 mib.len() as libc::c_uint,
 299                 path.as_ptr() as *mut libc::c_void,
 300                 &mut path_len,
 301                 ptr::null(),
 302                 0,
 303             ))?;
 304             path.set_len(path_len - 1); // chop off NUL
 305             Ok(PathBuf::from(OsString::from_vec(path)))
 306         }
 307     }
 308     fn procfs() -> io::Result<PathBuf> {
 309         let curproc_exe = path::Path::new("/proc/curproc/exe");
 310         if curproc_exe.is_file() {
 311             return crate::fs::read_link(curproc_exe);
 312         }
 313         Err(io::Error::new(
 314             io::ErrorKind::Other,
 315             "/proc/curproc/exe doesn't point to regular file.",
 316         ))
 317     }
 318     sysctl().or_else(|_| procfs())
 319 }
 320
 321 #[cfg(target_os = "openbsd")]
 322 pub fn current_exe() -> io::Result<PathBuf> {
 323     unsafe {
 324         let mut mib = [libc::CTL_KERN, libc::KERN_PROC_ARGS, libc::getpid(), libc::KERN_PROC_ARGV];
 325         let mib = mib.as_mut_ptr();
 326         let mut argv_len = 0;
 327         cvt(libc::sysctl(mib, 4, ptr::null_mut(), &mut argv_len, ptr::null_mut(), 0))?;
 328         let mut argv = Vec::<*const libc::c_char>::with_capacity(argv_len as usize);
 329         cvt(libc::sysctl(mib, 4, argv.as_mut_ptr() as *mut _, &mut argv_len, ptr::null_mut(), 0))?;
 330         argv.set_len(argv_len as usize);
 331         if argv[0].is_null() {
 332             return Err(io::Error::new(io::ErrorKind::Other, "no current exe available"));
 333         }
 334         let argv0 = CStr::from_ptr(argv[0]).to_bytes();
 335         if argv0[0] == b'.' || argv0.iter().any(|b| *b == b'/') {
 336             crate::fs::canonicalize(OsStr::from_bytes(argv0))
 337         } else {
 338             Ok(PathBuf::from(OsStr::from_bytes(argv0)))
 339         }
 340     }
 341 }
 342
 343 #[cfg(any(target_os = "linux", target_os = "android", target_os = "emscripten"))]
 344 pub fn current_exe() -> io::Result<PathBuf> {
 345     match crate::fs::read_link("/proc/self/exe") {
 346         Err(ref e) if e.kind() == io::ErrorKind::NotFound => Err(io::Error::new(
 347             io::ErrorKind::Other,
 348             "no /proc/self/exe available. Is /proc mounted?",
 349         )),
 350         other => other,
 351     }
 352 }
 353
 354 #[cfg(any(target_os = "macos", target_os = "ios"))]
 355 pub fn current_exe() -> io::Result<PathBuf> {
 356     extern "C" {
 357         fn _NSGetExecutablePath(buf: *mut libc::c_char, bufsize: *mut u32) -> libc::c_int;
 358     }
 359     unsafe {
 360         let mut sz: u32 = 0;
 361         _NSGetExecutablePath(ptr::null_mut(), &mut sz);
 362         if sz == 0 {
 363             return Err(io::Error::last_os_error());
 364         }
 365         let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
 366         let err = _NSGetExecutablePath(v.as_mut_ptr() as *mut i8, &mut sz);
 367         if err != 0 {
 368             return Err(io::Error::last_os_error());
 369         }
 370         v.set_len(sz as usize - 1); // chop off trailing NUL
 371         Ok(PathBuf::from(OsString::from_vec(v)))
 372     }
 373 }
 374
 375 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
 376 pub fn current_exe() -> io::Result<PathBuf> {
 377     extern "C" {
 378         fn getexecname() -> *const c_char;
 379     }
 380     unsafe {
 381         let path = getexecname();
 382         if path.is_null() {
 383             Err(io::Error::last_os_error())
 384         } else {
 385             let filename = CStr::from_ptr(path).to_bytes();
 386             let path = PathBuf::from(<OsStr as OsStrExt>::from_bytes(filename));
 387
 388             // Prepend a current working directory to the path if
 389             // it doesn't contain an absolute pathname.
 390             if filename[0] == b'/' { Ok(path) } else { getcwd().map(|cwd| cwd.join(path)) }
 391         }
 392     }
 393 }
 394
 395 #[cfg(target_os = "haiku")]
 396 pub fn current_exe() -> io::Result<PathBuf> {
 397     // Use Haiku's image info functions
 398     #[repr(C)]
 399     struct image_info {
 400         id: i32,
 401         type_: i32,
 402         sequence: i32,
 403         init_order: i32,
 404         init_routine: *mut libc::c_void, // function pointer
 405         term_routine: *mut libc::c_void, // function pointer
 406         device: libc::dev_t,
 407         node: libc::ino_t,
 408         name: [libc::c_char; 1024], // MAXPATHLEN
 409         text: *mut libc::c_void,
 410         data: *mut libc::c_void,
 411         text_size: i32,
 412         data_size: i32,
 413         api_version: i32,
 414         abi: i32,
 415     }
 416
 417     unsafe {
 418         extern "C" {
 419             fn _get_next_image_info(
 420                 team_id: i32,
 421                 cookie: *mut i32,
 422                 info: *mut image_info,
 423                 size: i32,
 424             ) -> i32;
 425         }
 426
 427         let mut info: image_info = mem::zeroed();
 428         let mut cookie: i32 = 0;
 429         // the executable can be found at team id 0
 430         let result =
 431             _get_next_image_info(0, &mut cookie, &mut info, mem::size_of::<image_info>() as i32);
 432         if result != 0 {
 433             use crate::io::ErrorKind;
 434             Err(io::Error::new(ErrorKind::Other, "Error getting executable path"))
 435         } else {
 436             let name = CStr::from_ptr(info.name.as_ptr()).to_bytes();
 437             Ok(PathBuf::from(OsStr::from_bytes(name)))
 438         }
 439     }
 440 }
 441
 442 #[cfg(target_os = "redox")]
 443 pub fn current_exe() -> io::Result<PathBuf> {
 444     crate::fs::read_to_string("sys:exe").map(PathBuf::from)
 445 }
 446
 447 #[cfg(any(target_os = "fuchsia", target_os = "l4re"))]
 448 pub fn current_exe() -> io::Result<PathBuf> {
 449     use crate::io::ErrorKind;
 450     Err(io::Error::new(ErrorKind::Other, "Not yet implemented!"))
 451 }
 452
 453 #[cfg(target_os = "vxworks")]
 454 pub fn current_exe() -> io::Result<PathBuf> {
 455     #[cfg(test)]
 456     use realstd::env;
 457
 458     #[cfg(not(test))]
 459     use crate::env;
 460
 461     let exe_path = env::args().next().unwrap();
 462     let path = path::Path::new(&exe_path);
 463     path.canonicalize()
 464 }
 465
 466 pub struct Env {
 467     iter: vec::IntoIter<(OsString, OsString)>,
 468     _dont_send_or_sync_me: PhantomData<*mut ()>,
 469 }
 470
 471 impl Iterator for Env {
 472     type Item = (OsString, OsString);
 473     fn next(&mut self) -> Option<(OsString, OsString)> {
 474         self.iter.next()
 475     }
 476     fn size_hint(&self) -> (usize, Option<usize>) {
 477         self.iter.size_hint()
 478     }
 479 }
 480
 481 #[cfg(target_os = "macos")]
 482 pub unsafe fn environ() -> *mut *const *const c_char {
 483     extern "C" {
 484         fn _NSGetEnviron() -> *mut *const *const c_char;
 485     }
 486     _NSGetEnviron()
 487 }
 488
 489 #[cfg(not(target_os = "macos"))]
 490 pub unsafe fn environ() -> *mut *const *const c_char {
 491     extern "C" {
 492         static mut environ: *const *const c_char;
 493     }
 494     ptr::addr_of_mut!(environ)
 495 }
 496
 497 static ENV_LOCK: StaticRWLock = StaticRWLock::new();
 498
 499 pub fn env_read_lock() -> RWLockReadGuard {
 500     ENV_LOCK.read_with_guard()
 501 }
 502
 503 /// Returns a vector of (variable, value) byte-vector pairs for all the
 504 /// environment variables of the current process.
 505 pub fn env() -> Env {
 506     unsafe {
 507         let _guard = env_read_lock();
 508         let mut environ = *environ();
 509         let mut result = Vec::new();
 510         if !environ.is_null() {
 511             while !(*environ).is_null() {
 512                 if let Some(key_value) = parse(CStr::from_ptr(*environ).to_bytes()) {
 513                     result.push(key_value);
 514                 }
 515                 environ = environ.add(1);
 516             }
 517         }
 518         return Env { iter: result.into_iter(), _dont_send_or_sync_me: PhantomData };
 519     }
 520
 521     fn parse(input: &[u8]) -> Option<(OsString, OsString)> {
 522         // Strategy (copied from glibc): Variable name and value are separated
 523         // by an ASCII equals sign '='. Since a variable name must not be
 524         // empty, allow variable names starting with an equals sign. Skip all
 525         // malformed lines.
 526         if input.is_empty() {
 527             return None;
 528         }
 529         let pos = memchr::memchr(b'=', &input[1..]).map(|p| p + 1);
 530         pos.map(|p| {
 531             (
 532                 OsStringExt::from_vec(input[..p].to_vec()),
 533                 OsStringExt::from_vec(input[p + 1..].to_vec()),
 534             )
 535         })
 536     }
 537 }
 538
 539 pub fn getenv(k: &OsStr) -> io::Result<Option<OsString>> {
 540     // environment variables with a nul byte can't be set, so their value is
 541     // always None as well
 542     let k = CString::new(k.as_bytes())?;
 543     unsafe {
 544         let _guard = env_read_lock();
 545         let s = libc::getenv(k.as_ptr()) as *const libc::c_char;
 546         let ret = if s.is_null() {
 547             None
 548         } else {
 549             Some(OsStringExt::from_vec(CStr::from_ptr(s).to_bytes().to_vec()))
 550         };
 551         Ok(ret)
 552     }
 553 }
 554
 555 pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
 556     let k = CString::new(k.as_bytes())?;
 557     let v = CString::new(v.as_bytes())?;
 558
 559     unsafe {
 560         let _guard = ENV_LOCK.write_with_guard();
 561         cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
 562     }
 563 }
 564
 565 pub fn unsetenv(n: &OsStr) -> io::Result<()> {
 566     let nbuf = CString::new(n.as_bytes())?;
 567
 568     unsafe {
 569         let _guard = ENV_LOCK.write_with_guard();
 570         cvt(libc::unsetenv(nbuf.as_ptr())).map(drop)
 571     }
 572 }
 573
 574 pub fn page_size() -> usize {
 575     unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
 576 }
 577
 578 pub fn temp_dir() -> PathBuf {
 579     crate::env::var_os("TMPDIR").map(PathBuf::from).unwrap_or_else(|| {
 580         if cfg!(target_os = "android") {
 581             PathBuf::from("/data/local/tmp")
 582         } else {
 583             PathBuf::from("/tmp")
 584         }
 585     })
 586 }
 587
 588 pub fn home_dir() -> Option<PathBuf> {
 589     return crate::env::var_os("HOME").or_else(|| unsafe { fallback() }).map(PathBuf::from);
 590
 591     #[cfg(any(
 592         target_os = "android",
 593         target_os = "ios",
 594         target_os = "emscripten",
 595         target_os = "redox",
 596         target_os = "vxworks"
 597     ))]
 598     unsafe fn fallback() -> Option<OsString> {
 599         None
 600     }
 601     #[cfg(not(any(
 602         target_os = "android",
 603         target_os = "ios",
 604         target_os = "emscripten",
 605         target_os = "redox",
 606         target_os = "vxworks"
 607     )))]
 608     unsafe fn fallback() -> Option<OsString> {
 609         let amt = match libc::sysconf(libc::_SC_GETPW_R_SIZE_MAX) {
 610             n if n < 0 => 512 as usize,
 611             n => n as usize,
 612         };
 613         let mut buf = Vec::with_capacity(amt);
 614         let mut passwd: libc::passwd = mem::zeroed();
 615         let mut result = ptr::null_mut();
 616         match libc::getpwuid_r(
 617             libc::getuid(),
 618             &mut passwd,
 619             buf.as_mut_ptr(),
 620             buf.capacity(),
 621             &mut result,
 622         ) {
 623             0 if !result.is_null() => {
 624                 let ptr = passwd.pw_dir as *const _;
 625                 let bytes = CStr::from_ptr(ptr).to_bytes().to_vec();
 626                 Some(OsStringExt::from_vec(bytes))
 627             }
 628             _ => None,
 629         }
 630     }
 631 }
 632
 633 pub fn exit(code: i32) -> ! {
 634     unsafe { libc::exit(code as c_int) }
 635 }
 636
 637 pub fn getpid() -> u32 {
 638     unsafe { libc::getpid() as u32 }
 639 }
 640
 641 pub fn getppid() -> u32 {
 642     unsafe { libc::getppid() as u32 }
 643 }
 644
 645 #[cfg(target_env = "gnu")]
 646 pub fn glibc_version() -> Option<(usize, usize)> {
 647     if let Some(Ok(version_str)) = glibc_version_cstr().map(CStr::to_str) {
 648         parse_glibc_version(version_str)
 649     } else {
 650         None
 651     }
 652 }
 653
 654 #[cfg(target_env = "gnu")]
 655 fn glibc_version_cstr() -> Option<&'static CStr> {
 656     weak! {
 657         fn gnu_get_libc_version() -> *const libc::c_char
 658     }
 659     if let Some(f) = gnu_get_libc_version.get() {
 660         unsafe { Some(CStr::from_ptr(f())) }
 661     } else {
 662         None
 663     }
 664 }
 665
 666 // Returns Some((major, minor)) if the string is a valid "x.y" version,
 667 // ignoring any extra dot-separated parts. Otherwise return None.
 668 #[cfg(target_env = "gnu")]
 669 fn parse_glibc_version(version: &str) -> Option<(usize, usize)> {
 670     let mut parsed_ints = version.split('.').map(str::parse::<usize>).fuse();
 671     match (parsed_ints.next(), parsed_ints.next()) {
 672         (Some(Ok(major)), Some(Ok(minor))) => Some((major, minor)),
 673         _ => None,
 674     }
 675 }