rust-analyzer-proc-macro-srv crashes when a custom allocator is preloaded

[andrewliebenow]

As described in oneapi-src/unified-runtime#803, the use of RTLD_DEEPBIND in dylib.rs [1] can cause rust-analyzer-proc-macro-srv to crash when a custom memory allocator is preloaded. The LD_PRELOAD environment variable is not propagated from Visual Studio Code to the rust-analyzer-proc-macro-srv process that eventually gets spawned, so on my machine, this issue only manifests when a custom allocator is specified in /etc/ld.so.preload.

Since it looks like the RTLD_DEEPBIND flag was deliberately added to address an issue, I would assume nothing can be done about this, and this issue can just serve as documentation.

Some of the error messages relating to this issue that I've seen:

proc-macro panicked: proc-macro server did not respond with data: proc-macro server did not respond with data

munmap_chunk(): invalid pointer

proc-macro server exited with signal: 6 (SIGABRT) (core dumped)

Depending on the custom allocator that is preloaded, these errors can vary. I think I also saw a SIGSEGV.

[1]

rust-analyzer/crates/proc-macro-srv/src/dylib.rs

Lines 51 to 75 in c54a827

	/// Loads dynamic library in platform dependent manner.
	///
	/// For unix, you have to use RTLD_DEEPBIND flag to escape problems described
	/// [here](https://github.com/fedochet/rust-proc-macro-panic-inside-panic-expample)
	/// and [here](https://github.com/rust-lang/rust/issues/60593).
	///
	/// Usage of RTLD_DEEPBIND
	/// [here](https://github.com/fedochet/rust-proc-macro-panic-inside-panic-expample/issues/1)
	///
	/// It seems that on Windows that behaviour is default, so we do nothing in that case.
	#[cfg(windows)]
	fn load_library(file: &Utf8Path) -> Result<Library, libloading::Error> {
	unsafe { Library::new(file) }
	}
	#[cfg(unix)]
	fn load_library(file: &Utf8Path) -> Result<Library, libloading::Error> {
	use libloading::os::unix::Library as UnixLibrary;
	use std::os::raw::c_int;
	const RTLD_NOW: c_int = 0x00002;
	const RTLD_DEEPBIND: c_int = 0x00008;
	unsafe { UnixLibrary::open(Some(file), RTLD_NOW | RTLD_DEEPBIND).map(|lib| lib.into()) }
	}

[Veykril]

It says right on the comment why, following the links in there it seems that this is a problem with the proc-macro bridge implementation, so there isn't really much we can do about that right now