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dladdr cannot leave dli_fname to be null #141239

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Merged
merged 1 commit into from
May 19, 2025
+5 −7
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dladdr cannot leave dli_fname to be null #141239

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4 changes: 1 addition & 3 deletions compiler/rustc_session/src/filesearch.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,9 +82,7 @@ fn current_dll_path() -> Result<PathBuf, String> {
let fname_ptr = info.dli_fname.as_ptr();
#[cfg(not(target_os = "cygwin"))]
let fname_ptr = {
if info.dli_fname.is_null() {
return Err("dladdr returned null pointer".into());
}
assert!(!info.dli_fname.is_null(), "the docs do not allow dladdr to be null");
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maybe "do not allow dli_fname to be null" ? as you pointed out, dladdr can return 0, and dli_sname can be null.

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oops

info.dli_fname
};
let bytes = CStr::from_ptr(fname_ptr).to_bytes();
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8 changes: 4 additions & 4 deletions src/tools/miri/src/shims/native_lib.rs
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Expand Up @@ -92,8 +92,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
fn get_func_ptr_explicitly_from_lib(&mut self, link_name: Symbol) -> Option<CodePtr> {
let this = self.eval_context_mut();
// Try getting the function from the shared library.
// On windows `_lib_path` will be unused, hence the name starting with `_`.
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This comment was outdated, the entire module does not even get built on Windows.

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 {
match lib.get(link_name.as_str().as_bytes()) {
Ok(x) => x,
Expand All @@ -114,16 +113,17 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
// 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
// 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 {
if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
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;
assert!(!fname_ptr.is_null());
if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap()
!= _lib_path.to_str().unwrap()
!= lib_path.to_str().unwrap()
{
return None;
}
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