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Replace MinGW library hack with heuristic controlling link mode
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@mati865
mati865 committed Sep 1, 2020
1 parent 23f0ccf commit 770231e
Showing 1 changed file with 25 additions and 92 deletions.
117 changes: 25 additions & 92 deletions compiler/rustc_codegen_ssa/src/back/link.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1014,86 +1014,7 @@ fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
}
}

// Because windows-gnu target is meant to be self-contained for pure Rust code it bundles
// own mingw-w64 libraries. These libraries are usually not compatible with mingw-w64
// installed in the system. This breaks many cases where Rust is mixed with other languages
// (e.g. *-sys crates).
// We prefer system mingw-w64 libraries if they are available to avoid this issue.
fn get_crt_libs_path(sess: &Session) -> Option<PathBuf> {
fn find_exe_in_path<P>(exe_name: P) -> Option<PathBuf>
where
P: AsRef<Path>,
{
for dir in env::split_paths(&env::var_os("PATH")?) {
let full_path = dir.join(&exe_name);
if full_path.is_file() {
return Some(fix_windows_verbatim_for_gcc(&full_path));
}
}
None
}

fn probe(sess: &Session) -> Option<PathBuf> {
if let (linker, LinkerFlavor::Gcc) = linker_and_flavor(&sess) {
let linker_path = if cfg!(windows) && linker.extension().is_none() {
linker.with_extension("exe")
} else {
linker
};
if let Some(linker_path) = find_exe_in_path(linker_path) {
let mingw_arch = match &sess.target.target.arch {
x if x == "x86" => "i686",
x => x,
};
let mingw_bits = &sess.target.target.target_pointer_width;
let mingw_dir = format!("{}-w64-mingw32", mingw_arch);
// Here we have path/bin/gcc but we need path/
let mut path = linker_path;
path.pop();
path.pop();
// Loosely based on Clang MinGW driver
let probe_paths = vec![
path.join(&mingw_dir).join("lib"), // Typical path
path.join(&mingw_dir).join("sys-root/mingw/lib"), // Rare path
path.join(format!(
"lib/mingw/tools/install/mingw{}/{}/lib",
&mingw_bits, &mingw_dir
)), // Chocolatey is creative
];
for probe_path in probe_paths {
if probe_path.join("crt2.o").exists() {
return Some(probe_path);
};
}
};
};
None
}

let mut system_library_path = sess.system_library_path.borrow_mut();
match &*system_library_path {
Some(Some(compiler_libs_path)) => Some(compiler_libs_path.clone()),
Some(None) => None,
None => {
let path = probe(sess);
*system_library_path = Some(path.clone());
path
}
}
}

fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
// prefer system {,dll}crt2.o libs, see get_crt_libs_path comment for more details
if sess.opts.cg.link_self_contained.is_none()
&& sess.target.target.llvm_target.contains("windows-gnu")
{
if let Some(compiler_libs_path) = get_crt_libs_path(sess) {
let file_path = compiler_libs_path.join(name);
if file_path.exists() {
return file_path;
}
}
}
let fs = sess.target_filesearch(PathKind::Native);
let file_path = fs.get_lib_path().join(name);
if file_path.exists() {
Expand Down Expand Up @@ -1286,6 +1207,28 @@ fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
}
}

// Returns true if linker is located within sysroot
fn detect_self_contained_mingw(sess: &Session) -> bool {
let (linker, _) = linker_and_flavor(&sess);
// Assume `-C linker=rust-lld` as self-contained mode
if linker == Path::new("rust-lld") {
return true;
}
let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
linker.with_extension("exe")
} else {
linker
};
for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
let full_path = dir.join(&linker_with_extension);
// If linker comes from sysroot assume self-contained mode
if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
return false;
}
}
true
}

/// Whether we link to our own CRT objects instead of relying on gcc to pull them.
/// We only provide such support for a very limited number of targets.
fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
Expand All @@ -1298,10 +1241,10 @@ fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
// based on host and linker path, for example.
// (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
// FIXME: Find some heuristic for "native mingw toolchain is available",
// likely based on `get_crt_libs_path` (https://github.com/rust-lang/rust/pull/67429).
Some(CrtObjectsFallback::Mingw) => {
sess.host == sess.target.target && sess.target.target.target_vendor != "uwp"
sess.host == sess.target.target
&& sess.target.target.target_vendor != "uwp"
&& detect_self_contained_mingw(&sess)
}
// FIXME: Figure out cases in which WASM needs to link with a native toolchain.
Some(CrtObjectsFallback::Wasm) => true,
Expand Down Expand Up @@ -1498,16 +1441,6 @@ fn link_local_crate_native_libs_and_dependent_crate_libs<'a, B: ArchiveBuilder<'

/// Add sysroot and other globally set directories to the directory search list.
fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
// Prefer system mingw-w64 libs, see get_crt_libs_path comment for more details.
if sess.opts.cg.link_self_contained.is_none()
&& cfg!(windows)
&& sess.target.target.llvm_target.contains("windows-gnu")
{
if let Some(compiler_libs_path) = get_crt_libs_path(sess) {
cmd.include_path(&compiler_libs_path);
}
}

// The default library location, we need this to find the runtime.
// The location of crates will be determined as needed.
let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
Expand Down

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