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Cygwin support in rustc #140154

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49553be
Experimental cygwin support in rustc
Berrysoft Apr 22, 2025
12fda86
Fix exe() to make rustc wrapper happy
Berrysoft May 9, 2025
5e048e0
Simplify current_dll_path for Cygwin
Berrysoft May 16, 2025
12c8fb8
Fix fname for miri
Berrysoft May 16, 2025
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1 change: 1 addition & 0 deletions compiler/rustc_llvm/build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,7 @@ fn main() {
} else if target.contains("haiku")
|| target.contains("darwin")
|| (is_crossed && (target.contains("dragonfly") || target.contains("solaris")))
|| target.contains("cygwin")
{
println!("cargo:rustc-link-lib=z");
} else if target.contains("netbsd") {
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14 changes: 10 additions & 4 deletions compiler/rustc_session/src/filesearch.rs
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Expand Up @@ -78,10 +78,16 @@ fn current_dll_path() -> Result<PathBuf, String> {
if libc::dladdr(addr, &mut info) == 0 {
return Err("dladdr failed".into());
}
if info.dli_fname.is_null() {
return Err("dladdr returned null pointer".into());
}
let bytes = CStr::from_ptr(info.dli_fname).to_bytes();
#[cfg(target_os = "cygwin")]
let fname_ptr = info.dli_fname.as_ptr();
#[cfg(not(target_os = "cygwin"))]
let fname_ptr = {
if info.dli_fname.is_null() {
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Hm, this can be null? I can't find that in the docs. Miri seems to assume it's never null...

(This is pre-existing, not new in this PR.)

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@jeremyd2019 jeremyd2019 May 16, 2025 •
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https://man7.org/linux/man-pages/man3/dladdr.3.html

If the address specified in addr could not be matched to a shared
object, then these functions return 0. In this case, an error
message is not available via dlerror(3).

My read of that is that either it finds a shared object, in which case dli_fname is valid, or else it will return 0 (but not tell you why in dlerror).

return Err("dladdr returned null pointer".into());
}
info.dli_fname
};
let bytes = CStr::from_ptr(fname_ptr).to_bytes();
let os = OsStr::from_bytes(bytes);
Ok(PathBuf::from(os))
}
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2 changes: 1 addition & 1 deletion src/bootstrap/src/core/builder/mod.rs
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Expand Up @@ -1388,7 +1388,7 @@ impl<'a> Builder<'a> {
// Windows doesn't need dylib path munging because the dlls for the
// compiler live next to the compiler and the system will find them
// automatically.
if cfg!(windows) {
if cfg!(any(windows, target_os = "cygwin")) {
return;
}

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2 changes: 1 addition & 1 deletion src/bootstrap/src/utils/helpers.rs
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Expand Up @@ -130,7 +130,7 @@ pub fn is_debug_info(name: &str) -> bool {
/// Returns the corresponding relative library directory that the compiler's
/// dylibs will be found in.
pub fn libdir(target: TargetSelection) -> &'static str {
if target.is_windows() { "bin" } else { "lib" }
if target.is_windows() || target.contains("cygwin") { "bin" } else { "lib" }
}

/// Adds a list of lookup paths to `cmd`'s dynamic library lookup path.
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2 changes: 1 addition & 1 deletion src/bootstrap/src/utils/shared_helpers.rs
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Expand Up @@ -20,7 +20,7 @@ use std::str::FromStr;
/// Returns the environment variable which the dynamic library lookup path
/// resides in for this platform.
pub fn dylib_path_var() -> &'static str {
if cfg!(target_os = "windows") {
if cfg!(any(target_os = "windows", target_os = "cygwin")) {
"PATH"
} else if cfg!(target_vendor = "apple") {
"DYLD_LIBRARY_PATH"
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7 changes: 6 additions & 1 deletion src/tools/miri/src/shims/native_lib.rs
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Expand Up @@ -117,7 +117,12 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit();
unsafe {
if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
if std::ffi::CStr::from_ptr(info.assume_init().dli_fname).to_str().unwrap()
let info = info.assume_init();
#[cfg(target_os = "cygwin")]
let fname_ptr = info.dli_fname.as_ptr();
#[cfg(not(target_os = "cygwin"))]
let fname_ptr = info.dli_fname;
if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap()
!= _lib_path.to_str().unwrap()
{
return None;
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