From 090a968fe7680cce0d3aa8fde25a5dc48948e43e Mon Sep 17 00:00:00 2001 From: Ryan Cumming Date: Wed, 10 Jan 2018 20:13:03 +1100 Subject: Only link res_init() on GNU/*nix To workaround a bug in glibc <= 2.26 lookup_host() calls res_init() based on the glibc version detected at runtime. While this avoids calling res_init() on platforms where it's not required we will still end up linking against the symbol. This causes an issue on macOS where res_init() is implemented in a separate library (libresolv.9.dylib) from the main libc. While this is harmless for standalone programs it becomes a problem if Rust code is statically linked against another program. If the linked program doesn't already specify -lresolv it will cause the link to fail. This is captured in issue #46797 Fix this by hooking in to the glibc workaround in `cvt_gai` and only activating it for the "gnu" environment on Unix This should include all glibc platforms while excluding musl, windows-gnu, macOS, FreeBSD, etc. This has the side benefit of removing the #[cfg] in sys_common; only unix.rs has code related to the workaround now. --- src/libstd/sys_common/net.rs | 24 +++--------------------- 1 file changed, 3 insertions(+), 21 deletions(-) (limited to 'src/libstd/sys_common') diff --git a/src/libstd/sys_common/net.rs b/src/libstd/sys_common/net.rs index c70b39995eb..b841afe1a51 100644 --- a/src/libstd/sys_common/net.rs +++ b/src/libstd/sys_common/net.rs @@ -166,27 +166,9 @@ pub fn lookup_host(host: &str) -> io::Result { hints.ai_socktype = c::SOCK_STREAM; let mut res = ptr::null_mut(); unsafe { - match cvt_gai(c::getaddrinfo(c_host.as_ptr(), ptr::null(), &hints, &mut res)) { - Ok(_) => { - Ok(LookupHost { original: res, cur: res }) - }, - #[cfg(unix)] - Err(e) => { - // If we're running glibc prior to version 2.26, the lookup - // failure could be caused by caching a stale /etc/resolv.conf. - // We need to call libc::res_init() to clear the cache. But we - // shouldn't call it in on any other platform, because other - // res_init implementations aren't thread-safe. See - // https://github.com/rust-lang/rust/issues/41570 and - // https://github.com/rust-lang/rust/issues/43592. - use sys::net::res_init_if_glibc_before_2_26; - let _ = res_init_if_glibc_before_2_26(); - Err(e) - }, - // the cfg is needed here to avoid an "unreachable pattern" warning - #[cfg(not(unix))] - Err(e) => Err(e), - } + cvt_gai(c::getaddrinfo(c_host.as_ptr(), ptr::null(), &hints, &mut res)).map(|_| { + LookupHost { original: res, cur: res } + }) } } -- cgit 1.4.1-3-g733a5