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Rollup merge of #141239 - RalfJung:dladdr-fname, r=Noratrieb

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dladdr cannot leave dli_fname to be null

There are two places in the repo calling `dladdr`, and they are inconsistent wrt their assumption of whether the `dli_fname` field can be null. Let's make them consistent. I see nothing in the docs that allows it to be null, but just to be on the safe side let's make this an assertion so hopefully we get a report if that ever happens.
This commit is contained in:
Stuart Cook
2025-05-19 21:10:44 +10:00
committed by GitHub
parent 1d5c35a52d d22f53b970
commit b86de538ce
2 changed files with 5 additions and 7 deletions
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4
compiler/rustc_session/src/filesearch.rs
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@@ -82,9 +82,7 @@ fn current_dll_path() -> Result<PathBuf, String> {
let fname_ptr = info.dli_fname.as_ptr(); let fname_ptr = info.dli_fname.as_ptr();
#[cfg(not(target_os = "cygwin"))] #[cfg(not(target_os = "cygwin"))]
let fname_ptr = { let fname_ptr = {
if info.dli_fname.is_null() { assert!(!info.dli_fname.is_null(), "the docs do not allow dladdr to be null");
return Err("dladdr returned null pointer".into());
}
info.dli_fname info.dli_fname
}; };
let bytes = CStr::from_ptr(fname_ptr).to_bytes(); let bytes = CStr::from_ptr(fname_ptr).to_bytes();

8
src/tools/miri/src/shims/native_lib.rs
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@@ -92,8 +92,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
fn get_func_ptr_explicitly_from_lib(&mut self, link_name: Symbol) -> Option<CodePtr> { fn get_func_ptr_explicitly_from_lib(&mut self, link_name: Symbol) -> Option<CodePtr> {
let this = self.eval_context_mut(); let this = self.eval_context_mut();
// Try getting the function from the shared library. // Try getting the function from the shared library.
// On windows `_lib_path` will be unused, hence the name starting with `_`. let (lib, lib_path) = this.machine.native_lib.as_ref().unwrap();
let (lib, _lib_path) = this.machine.native_lib.as_ref().unwrap();
let func: libloading::Symbol<'_, unsafe extern "C" fn()> = unsafe { let func: libloading::Symbol<'_, unsafe extern "C" fn()> = unsafe {
match lib.get(link_name.as_str().as_bytes()) { match lib.get(link_name.as_str().as_bytes()) {
Ok(x) => x, Ok(x) => x,
@@ -114,7 +113,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
// This code is a reimplementation of the mechanism for getting `dli_fname` in `libloading`, // This code is a reimplementation of the mechanism for getting `dli_fname` in `libloading`,
// from: https://docs.rs/libloading/0.7.3/src/libloading/os/unix/mod.rs.html#411 // from: https://docs.rs/libloading/0.7.3/src/libloading/os/unix/mod.rs.html#411
// using the `libc` crate where this interface is public. // using the `libc` crate where this interface is public.
let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit(); let mut info = std::mem::MaybeUninit::<libc::Dl_info>::zeroed();
unsafe { unsafe {
if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 { if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
let info = info.assume_init(); let info = info.assume_init();
@@ -122,8 +121,9 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
let fname_ptr = info.dli_fname.as_ptr(); let fname_ptr = info.dli_fname.as_ptr();
#[cfg(not(target_os = "cygwin"))] #[cfg(not(target_os = "cygwin"))]
let fname_ptr = info.dli_fname; let fname_ptr = info.dli_fname;
assert!(!fname_ptr.is_null());
if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap() if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap()
!= _lib_path.to_str().unwrap() != lib_path.to_str().unwrap()
{ {
return None; return None;
} }