install_fatal_error_handler is unsound.

[ErisianArchitect]

Describe the Bug

inkwell/src/support/error_handling.rs

Line 26 in e44cdb9

pub unsafe fn install_fatal_error_handler(handler: extern "C" fn(*const ::libc::c_char)) {

This function is unsound, unless the error handler calls abort. If the error handler panics, then the panic will unwind into the C++ stack frames, which is unsound and would cause undefined behavior.

I'm not entirely sure if we can make this sound. We can notify users of the behavior and tell them that they should abort and not return from the function.

[TheDan64]

I agree, I think I originally thought that it reported errors this way and we could use it internally but that's not the case

[TheDan64]

I might be wrong, but I think we could make it safe(r?) by using std::panic::catch_unwind on the rust code being called (suppose we take a closure to run instead)

[ErisianArchitect]

The problem is that we'd still need to pass control back to LLVM, which is going to abort anyway.

I don't know if there's much benefit in having this error handler in the first place for a safe wrapper in Rust.