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(test)]
   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::mem;
  16 use crate::path::{self, PathBuf};
  17 use crate::ptr;
  18 use crate::slice;
  19 use crate::str;
  20 use crate::sys::cvt;
  21 use crate::sys::fd;
  22 use crate::sys::memchr;
  23 use crate::sys_common::rwlock::{StaticRwLock, StaticRwLockReadGuard};
  24 use crate::vec;
  25
  26 #[cfg(all(target_env = "gnu", not(target_os = "vxworks")))]
  27 use crate::sys::weak::weak;
  28
  29 use libc::{c_char, c_int, c_void};
  30
  31 const TMPBUF_SZ: usize = 128;
  32
  33 cfg_if::cfg_if! {
  34     if #[cfg(target_os = "redox")] {
  35         const PATH_SEPARATOR: u8 = b';';
  36     } else {
  37         const PATH_SEPARATOR: u8 = b':';
  38     }
  39 }
  40
  41 extern "C" {
  42     #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
  43     #[cfg_attr(
  44         any(
  45             target_os = "linux",
  46             target_os = "emscripten",
  47             target_os = "fuchsia",
  48             target_os = "l4re"
  49         ),
  50         link_name = "__errno_location"
  51     )]
  52     #[cfg_attr(
  53         any(
  54             target_os = "netbsd",
  55             target_os = "openbsd",
  56             target_os = "android",
  57             target_os = "redox",
  58             target_env = "newlib"
  59         ),
  60         link_name = "__errno"
  61     )]
  62     #[cfg_attr(any(target_os = "solaris", target_os = "illumos"), link_name = "___errno")]
  63     #[cfg_attr(
  64         any(target_os = "macos", target_os = "ios", target_os = "freebsd"),
  65         link_name = "__error"
  66     )]
  67     #[cfg_attr(target_os = "haiku", link_name = "_errnop")]
  68     fn errno_location() -> *mut c_int;
  69 }
  70
  71 /// Returns the platform-specific value of errno
  72 #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
  73 pub fn errno() -> i32 {
  74     unsafe { (*errno_location()) as i32 }
  75 }
  76
  77 /// Sets the platform-specific value of errno
  78 #[cfg(all(not(target_os = "dragonfly"), not(target_os = "vxworks")))] // needed for readdir and syscall!
  79 #[allow(dead_code)] // but not all target cfgs actually end up using it
  80 pub fn set_errno(e: i32) {
  81     unsafe { *errno_location() = e as c_int }
  82 }
  83
  84 #[cfg(target_os = "vxworks")]
  85 pub fn errno() -> i32 {
  86     unsafe { libc::errnoGet() }
  87 }
  88
  89 #[cfg(target_os = "dragonfly")]
  90 pub fn errno() -> i32 {
  91     extern "C" {
  92         #[thread_local]
  93         static errno: c_int;
  94     }
  95
  96     unsafe { errno as i32 }
  97 }
  98
  99 #[cfg(target_os = "dragonfly")]
 100 #[allow(dead_code)]
 101 pub fn set_errno(e: i32) {
 102     extern "C" {
 103         #[thread_local]
 104         static mut errno: c_int;
 105     }
 106
 107     unsafe {
 108         errno = e;
 109     }
 110 }
 111
 112 /// Gets a detailed string description for the given error number.
 113 pub fn error_string(errno: i32) -> String {
 114     extern "C" {
 115         #[cfg_attr(any(target_os = "linux", target_env = "newlib"), link_name = "__xpg_strerror_r")]
 116         fn strerror_r(errnum: c_int, buf: *mut c_char, buflen: libc::size_t) -> c_int;
 117     }
 118
 119     let mut buf = [0 as c_char; TMPBUF_SZ];
 120
 121     let p = buf.as_mut_ptr();
 122     unsafe {
 123         if strerror_r(errno as c_int, p, buf.len()) < 0 {
 124             panic!("strerror_r failure");
 125         }
 126
 127         let p = p as *const _;
 128         str::from_utf8(CStr::from_ptr(p).to_bytes()).unwrap().to_owned()
 129     }
 130 }
 131
 132 #[cfg(target_os = "espidf")]
 133 pub fn getcwd() -> io::Result<PathBuf> {
 134     Ok(PathBuf::from("/"))
 135 }
 136
 137 #[cfg(not(target_os = "espidf"))]
 138 pub fn getcwd() -> io::Result<PathBuf> {
 139     let mut buf = Vec::with_capacity(512);
 140     loop {
 141         unsafe {
 142             let ptr = buf.as_mut_ptr() as *mut libc::c_char;
 143             if !libc::getcwd(ptr, buf.capacity()).is_null() {
 144                 let len = CStr::from_ptr(buf.as_ptr() as *const libc::c_char).to_bytes().len();
 145                 buf.set_len(len);
 146                 buf.shrink_to_fit();
 147                 return Ok(PathBuf::from(OsString::from_vec(buf)));
 148             } else {
 149                 let error = io::Error::last_os_error();
 150                 if error.raw_os_error() != Some(libc::ERANGE) {
 151                     return Err(error);
 152                 }
 153             }
 154
 155             // Trigger the internal buffer resizing logic of `Vec` by requiring
 156             // more space than the current capacity.
 157             let cap = buf.capacity();
 158             buf.set_len(cap);
 159             buf.reserve(1);
 160         }
 161     }
 162 }
 163
 164 #[cfg(target_os = "espidf")]
 165 pub fn chdir(p: &path::Path) -> io::Result<()> {
 166     super::unsupported::unsupported()
 167 }
 168
 169 #[cfg(not(target_os = "espidf"))]
 170 pub fn chdir(p: &path::Path) -> io::Result<()> {
 171     let p: &OsStr = p.as_ref();
 172     let p = CString::new(p.as_bytes())?;
 173     if unsafe { libc::chdir(p.as_ptr()) } != 0 {
 174         return Err(io::Error::last_os_error());
 175     }
 176     Ok(())
 177 }
 178
 179 pub struct SplitPaths<'a> {
 180     iter: iter::Map<slice::Split<'a, u8, fn(&u8) -> bool>, fn(&'a [u8]) -> PathBuf>,
 181 }
 182
 183 pub fn split_paths(unparsed: &OsStr) -> SplitPaths<'_> {
 184     fn bytes_to_path(b: &[u8]) -> PathBuf {
 185         PathBuf::from(<OsStr as OsStrExt>::from_bytes(b))
 186     }
 187     fn is_separator(b: &u8) -> bool {
 188         *b == PATH_SEPARATOR
 189     }
 190     let unparsed = unparsed.as_bytes();
 191     SplitPaths {
 192         iter: unparsed
 193             .split(is_separator as fn(&u8) -> bool)
 194             .map(bytes_to_path as fn(&[u8]) -> PathBuf),
 195     }
 196 }
 197
 198 impl<'a> Iterator for SplitPaths<'a> {
 199     type Item = PathBuf;
 200     fn next(&mut self) -> Option<PathBuf> {
 201         self.iter.next()
 202     }
 203     fn size_hint(&self) -> (usize, Option<usize>) {
 204         self.iter.size_hint()
 205     }
 206 }
 207
 208 #[derive(Debug)]
 209 pub struct JoinPathsError;
 210
 211 pub fn join_paths<I, T>(paths: I) -> Result<OsString, JoinPathsError>
 212 where
 213     I: Iterator<Item = T>,
 214     T: AsRef<OsStr>,
 215 {
 216     let mut joined = Vec::new();
 217
 218     for (i, path) in paths.enumerate() {
 219         let path = path.as_ref().as_bytes();
 220         if i > 0 {
 221             joined.push(PATH_SEPARATOR)
 222         }
 223         if path.contains(&PATH_SEPARATOR) {
 224             return Err(JoinPathsError);
 225         }
 226         joined.extend_from_slice(path);
 227     }
 228     Ok(OsStringExt::from_vec(joined))
 229 }
 230
 231 impl fmt::Display for JoinPathsError {
 232     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 233         write!(f, "path segment contains separator `{}`", char::from(PATH_SEPARATOR))
 234     }
 235 }
 236
 237 impl StdError for JoinPathsError {
 238     #[allow(deprecated)]
 239     fn description(&self) -> &str {
 240         "failed to join paths"
 241     }
 242 }
 243
 244 #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
 245 pub fn current_exe() -> io::Result<PathBuf> {
 246     unsafe {
 247         let mut mib = [
 248             libc::CTL_KERN as c_int,
 249             libc::KERN_PROC as c_int,
 250             libc::KERN_PROC_PATHNAME as c_int,
 251             -1 as c_int,
 252         ];
 253         let mut sz = 0;
 254         cvt(libc::sysctl(
 255             mib.as_mut_ptr(),
 256             mib.len() as libc::c_uint,
 257             ptr::null_mut(),
 258             &mut sz,
 259             ptr::null_mut(),
 260             0,
 261         ))?;
 262         if sz == 0 {
 263             return Err(io::Error::last_os_error());
 264         }
 265         let mut v: Vec<u8> = Vec::with_capacity(sz);
 266         cvt(libc::sysctl(
 267             mib.as_mut_ptr(),
 268             mib.len() as libc::c_uint,
 269             v.as_mut_ptr() as *mut libc::c_void,
 270             &mut sz,
 271             ptr::null_mut(),
 272             0,
 273         ))?;
 274         if sz == 0 {
 275             return Err(io::Error::last_os_error());
 276         }
 277         v.set_len(sz - 1); // chop off trailing NUL
 278         Ok(PathBuf::from(OsString::from_vec(v)))
 279     }
 280 }
 281
 282 #[cfg(target_os = "netbsd")]
 283 pub fn current_exe() -> io::Result<PathBuf> {
 284     fn sysctl() -> io::Result<PathBuf> {
 285         unsafe {
 286             let mib = [libc::CTL_KERN, libc::KERN_PROC_ARGS, -1, libc::KERN_PROC_PATHNAME];
 287             let mut path_len: usize = 0;
 288             cvt(libc::sysctl(
 289                 mib.as_ptr(),
 290                 mib.len() as libc::c_uint,
 291                 ptr::null_mut(),
 292                 &mut path_len,
 293                 ptr::null(),
 294                 0,
 295             ))?;
 296             if path_len <= 1 {
 297                 return Err(io::const_io_error!(
 298                     io::ErrorKind::Uncategorized,
 299                     "KERN_PROC_PATHNAME sysctl returned zero-length string",
 300                 ));
 301             }
 302             let mut path: Vec<u8> = Vec::with_capacity(path_len);
 303             cvt(libc::sysctl(
 304                 mib.as_ptr(),
 305                 mib.len() as libc::c_uint,
 306                 path.as_ptr() as *mut libc::c_void,
 307                 &mut path_len,
 308                 ptr::null(),
 309                 0,
 310             ))?;
 311             path.set_len(path_len - 1); // chop off NUL
 312             Ok(PathBuf::from(OsString::from_vec(path)))
 313         }
 314     }
 315     fn procfs() -> io::Result<PathBuf> {
 316         let curproc_exe = path::Path::new("/proc/curproc/exe");
 317         if curproc_exe.is_file() {
 318             return crate::fs::read_link(curproc_exe);
 319         }
 320         Err(io::const_io_error!(
 321             io::ErrorKind::Uncategorized,
 322             "/proc/curproc/exe doesn't point to regular file.",
 323         ))
 324     }
 325     sysctl().or_else(|_| procfs())
 326 }
 327
 328 #[cfg(target_os = "openbsd")]
 329 pub fn current_exe() -> io::Result<PathBuf> {
 330     unsafe {
 331         let mut mib = [libc::CTL_KERN, libc::KERN_PROC_ARGS, libc::getpid(), libc::KERN_PROC_ARGV];
 332         let mib = mib.as_mut_ptr();
 333         let mut argv_len = 0;
 334         cvt(libc::sysctl(mib, 4, ptr::null_mut(), &mut argv_len, ptr::null_mut(), 0))?;
 335         let mut argv = Vec::<*const libc::c_char>::with_capacity(argv_len as usize);
 336         cvt(libc::sysctl(mib, 4, argv.as_mut_ptr() as *mut _, &mut argv_len, ptr::null_mut(), 0))?;
 337         argv.set_len(argv_len as usize);
 338         if argv[0].is_null() {
 339             return Err(io::const_io_error!(
 340                 io::ErrorKind::Uncategorized,
 341                 "no current exe available",
 342             ));
 343         }
 344         let argv0 = CStr::from_ptr(argv[0]).to_bytes();
 345         if argv0[0] == b'.' || argv0.iter().any(|b| *b == b'/') {
 346             crate::fs::canonicalize(OsStr::from_bytes(argv0))
 347         } else {
 348             Ok(PathBuf::from(OsStr::from_bytes(argv0)))
 349         }
 350     }
 351 }
 352
 353 #[cfg(any(target_os = "linux", target_os = "android", target_os = "emscripten"))]
 354 pub fn current_exe() -> io::Result<PathBuf> {
 355     match crate::fs::read_link("/proc/self/exe") {
 356         Err(ref e) if e.kind() == io::ErrorKind::NotFound => Err(io::const_io_error!(
 357             io::ErrorKind::Uncategorized,
 358             "no /proc/self/exe available. Is /proc mounted?",
 359         )),
 360         other => other,
 361     }
 362 }
 363
 364 #[cfg(any(target_os = "macos", target_os = "ios"))]
 365 pub fn current_exe() -> io::Result<PathBuf> {
 366     unsafe {
 367         let mut sz: u32 = 0;
 368         libc::_NSGetExecutablePath(ptr::null_mut(), &mut sz);
 369         if sz == 0 {
 370             return Err(io::Error::last_os_error());
 371         }
 372         let mut v: Vec<u8> = Vec::with_capacity(sz as usize);
 373         let err = libc::_NSGetExecutablePath(v.as_mut_ptr() as *mut i8, &mut sz);
 374         if err != 0 {
 375             return Err(io::Error::last_os_error());
 376         }
 377         v.set_len(sz as usize - 1); // chop off trailing NUL
 378         Ok(PathBuf::from(OsString::from_vec(v)))
 379     }
 380 }
 381
 382 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
 383 pub fn current_exe() -> io::Result<PathBuf> {
 384     if let Ok(path) = crate::fs::read_link("/proc/self/path/a.out") {
 385         Ok(path)
 386     } else {
 387         unsafe {
 388             let path = libc::getexecname();
 389             if path.is_null() {
 390                 Err(io::Error::last_os_error())
 391             } else {
 392                 let filename = CStr::from_ptr(path).to_bytes();
 393                 let path = PathBuf::from(<OsStr as OsStrExt>::from_bytes(filename));
 394
 395                 // Prepend a current working directory to the path if
 396                 // it doesn't contain an absolute pathname.
 397                 if filename[0] == b'/' { Ok(path) } else { getcwd().map(|cwd| cwd.join(path)) }
 398             }
 399         }
 400     }
 401 }
 402
 403 #[cfg(target_os = "haiku")]
 404 pub fn current_exe() -> io::Result<PathBuf> {
 405     unsafe {
 406         let mut info: mem::MaybeUninit<libc::image_info> = mem::MaybeUninit::uninit();
 407         let mut cookie: i32 = 0;
 408         // the executable can be found at team id 0
 409         let result = libc::_get_next_image_info(
 410             0,
 411             &mut cookie,
 412             info.as_mut_ptr(),
 413             mem::size_of::<libc::image_info>(),
 414         );
 415         if result != 0 {
 416             use crate::io::ErrorKind;
 417             Err(io::const_io_error!(ErrorKind::Uncategorized, "Error getting executable path"))
 418         } else {
 419             let name = CStr::from_ptr((*info.as_ptr()).name.as_ptr()).to_bytes();
 420             Ok(PathBuf::from(OsStr::from_bytes(name)))
 421         }
 422     }
 423 }
 424
 425 #[cfg(target_os = "redox")]
 426 pub fn current_exe() -> io::Result<PathBuf> {
 427     crate::fs::read_to_string("sys:exe").map(PathBuf::from)
 428 }
 429
 430 #[cfg(target_os = "l4re")]
 431 pub fn current_exe() -> io::Result<PathBuf> {
 432     use crate::io::ErrorKind;
 433     Err(io::const_io_error!(ErrorKind::Unsupported, "Not yet implemented!"))
 434 }
 435
 436 #[cfg(target_os = "vxworks")]
 437 pub fn current_exe() -> io::Result<PathBuf> {
 438     #[cfg(test)]
 439     use realstd::env;
 440
 441     #[cfg(not(test))]
 442     use crate::env;
 443
 444     let exe_path = env::args().next().unwrap();
 445     let path = path::Path::new(&exe_path);
 446     path.canonicalize()
 447 }
 448
 449 #[cfg(target_os = "espidf")]
 450 pub fn current_exe() -> io::Result<PathBuf> {
 451     super::unsupported::unsupported()
 452 }
 453
 454 #[cfg(target_os = "fuchsia")]
 455 pub fn current_exe() -> io::Result<PathBuf> {
 456     use crate::io::ErrorKind;
 457
 458     #[cfg(test)]
 459     use realstd::env;
 460
 461     #[cfg(not(test))]
 462     use crate::env;
 463
 464     let exe_path = env::args().next().ok_or(io::const_io_error!(
 465         ErrorKind::Uncategorized,
 466         "an executable path was not found because no arguments were provided through argv"
 467     ))?;
 468     let path = PathBuf::from(exe_path);
 469
 470     // Prepend the current working directory to the path if it's not absolute.
 471     if !path.is_absolute() { getcwd().map(|cwd| cwd.join(path)) } else { Ok(path) }
 472 }
 473
 474 pub struct Env {
 475     iter: vec::IntoIter<(OsString, OsString)>,
 476 }
 477
 478 impl !Send for Env {}
 479 impl !Sync for Env {}
 480
 481 impl Iterator for Env {
 482     type Item = (OsString, OsString);
 483     fn next(&mut self) -> Option<(OsString, OsString)> {
 484         self.iter.next()
 485     }
 486     fn size_hint(&self) -> (usize, Option<usize>) {
 487         self.iter.size_hint()
 488     }
 489 }
 490
 491 #[cfg(target_os = "macos")]
 492 pub unsafe fn environ() -> *mut *const *const c_char {
 493     libc::_NSGetEnviron() as *mut *const *const c_char
 494 }
 495
 496 #[cfg(not(target_os = "macos"))]
 497 pub unsafe fn environ() -> *mut *const *const c_char {
 498     extern "C" {
 499         static mut environ: *const *const c_char;
 500     }
 501     ptr::addr_of_mut!(environ)
 502 }
 503
 504 static ENV_LOCK: StaticRwLock = StaticRwLock::new();
 505
 506 pub fn env_read_lock() -> StaticRwLockReadGuard {
 507     ENV_LOCK.read()
 508 }
 509
 510 /// Returns a vector of (variable, value) byte-vector pairs for all the
 511 /// environment variables of the current process.
 512 pub fn env() -> Env {
 513     unsafe {
 514         let _guard = env_read_lock();
 515         let mut environ = *environ();
 516         let mut result = Vec::new();
 517         if !environ.is_null() {
 518             while !(*environ).is_null() {
 519                 if let Some(key_value) = parse(CStr::from_ptr(*environ).to_bytes()) {
 520                     result.push(key_value);
 521                 }
 522                 environ = environ.add(1);
 523             }
 524         }
 525         return Env { iter: result.into_iter() };
 526     }
 527
 528     fn parse(input: &[u8]) -> Option<(OsString, OsString)> {
 529         // Strategy (copied from glibc): Variable name and value are separated
 530         // by an ASCII equals sign '='. Since a variable name must not be
 531         // empty, allow variable names starting with an equals sign. Skip all
 532         // malformed lines.
 533         if input.is_empty() {
 534             return None;
 535         }
 536         let pos = memchr::memchr(b'=', &input[1..]).map(|p| p + 1);
 537         pos.map(|p| {
 538             (
 539                 OsStringExt::from_vec(input[..p].to_vec()),
 540                 OsStringExt::from_vec(input[p + 1..].to_vec()),
 541             )
 542         })
 543     }
 544 }
 545
 546 pub fn getenv(k: &OsStr) -> Option<OsString> {
 547     // environment variables with a nul byte can't be set, so their value is
 548     // always None as well
 549     let k = CString::new(k.as_bytes()).ok()?;
 550     unsafe {
 551         let _guard = env_read_lock();
 552         let s = libc::getenv(k.as_ptr()) as *const libc::c_char;
 553         if s.is_null() {
 554             None
 555         } else {
 556             Some(OsStringExt::from_vec(CStr::from_ptr(s).to_bytes().to_vec()))
 557         }
 558     }
 559 }
 560
 561 pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
 562     let k = CString::new(k.as_bytes())?;
 563     let v = CString::new(v.as_bytes())?;
 564
 565     unsafe {
 566         let _guard = ENV_LOCK.write();
 567         cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
 568     }
 569 }
 570
 571 pub fn unsetenv(n: &OsStr) -> io::Result<()> {
 572     let nbuf = CString::new(n.as_bytes())?;
 573
 574     unsafe {
 575         let _guard = ENV_LOCK.write();
 576         cvt(libc::unsetenv(nbuf.as_ptr())).map(drop)
 577     }
 578 }
 579
 580 #[cfg(not(target_os = "espidf"))]
 581 pub fn page_size() -> usize {
 582     unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
 583 }
 584
 585 pub fn temp_dir() -> PathBuf {
 586     crate::env::var_os("TMPDIR").map(PathBuf::from).unwrap_or_else(|| {
 587         if cfg!(target_os = "android") {
 588             PathBuf::from("/data/local/tmp")
 589         } else {
 590             PathBuf::from("/tmp")
 591         }
 592     })
 593 }
 594
 595 pub fn home_dir() -> Option<PathBuf> {
 596     return crate::env::var_os("HOME").or_else(|| unsafe { fallback() }).map(PathBuf::from);
 597
 598     #[cfg(any(
 599         target_os = "android",
 600         target_os = "ios",
 601         target_os = "emscripten",
 602         target_os = "redox",
 603         target_os = "vxworks",
 604         target_os = "espidf"
 605     ))]
 606     unsafe fn fallback() -> Option<OsString> {
 607         None
 608     }
 609     #[cfg(not(any(
 610         target_os = "android",
 611         target_os = "ios",
 612         target_os = "emscripten",
 613         target_os = "redox",
 614         target_os = "vxworks",
 615         target_os = "espidf"
 616     )))]
 617     unsafe fn fallback() -> Option<OsString> {
 618         let amt = match libc::sysconf(libc::_SC_GETPW_R_SIZE_MAX) {
 619             n if n < 0 => 512 as usize,
 620             n => n as usize,
 621         };
 622         let mut buf = Vec::with_capacity(amt);
 623         let mut passwd: libc::passwd = mem::zeroed();
 624         let mut result = ptr::null_mut();
 625         match libc::getpwuid_r(
 626             libc::getuid(),
 627             &mut passwd,
 628             buf.as_mut_ptr(),
 629             buf.capacity(),
 630             &mut result,
 631         ) {
 632             0 if !result.is_null() => {
 633                 let ptr = passwd.pw_dir as *const _;
 634                 let bytes = CStr::from_ptr(ptr).to_bytes().to_vec();
 635                 Some(OsStringExt::from_vec(bytes))
 636             }
 637             _ => None,
 638         }
 639     }
 640 }
 641
 642 pub fn exit(code: i32) -> ! {
 643     unsafe { libc::exit(code as c_int) }
 644 }
 645
 646 pub fn getpid() -> u32 {
 647     unsafe { libc::getpid() as u32 }
 648 }
 649
 650 pub fn getppid() -> u32 {
 651     unsafe { libc::getppid() as u32 }
 652 }
 653
 654 #[cfg(all(target_os = "linux", target_env = "gnu"))]
 655 pub fn glibc_version() -> Option<(usize, usize)> {
 656     extern "C" {
 657         fn gnu_get_libc_version() -> *const libc::c_char;
 658     }
 659     let version_cstr = unsafe { CStr::from_ptr(gnu_get_libc_version()) };
 660     if let Ok(version_str) = version_cstr.to_str() {
 661         parse_glibc_version(version_str)
 662     } else {
 663         None
 664     }
 665 }
 666
 667 // Returns Some((major, minor)) if the string is a valid "x.y" version,
 668 // ignoring any extra dot-separated parts. Otherwise return None.
 669 #[cfg(all(target_os = "linux", target_env = "gnu"))]
 670 fn parse_glibc_version(version: &str) -> Option<(usize, usize)> {
 671     let mut parsed_ints = version.split('.').map(str::parse::<usize>).fuse();
 672     match (parsed_ints.next(), parsed_ints.next()) {
 673         (Some(Ok(major)), Some(Ok(minor))) => Some((major, minor)),
 674         _ => None,
 675     }
 676 }