rustc: malloc.c:2388: sysmalloc: Assertion failed

[cuviper]

I was playing with examples for #28179 and hit this assertion in the playpen.

fn main() {
  println!("ok")
}

#[no_mangle]
#[allow(non_snake_case)]
pub fn _ZN2io5stdio6_print20h94cd0587c9a534faX3gE() {
    std::process::exit(1);
}

That #[no_mangle] function needs to clash with rust's io::stdio::_print. This particular name is from stable 1.2. http://is.gd/YpEFlo

rustc: malloc.c:2388: sysmalloc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 *(sizeof(size_t))) - 1)) & ~((2 *(sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long) old_end & (pagesize - 1)) == 0)' failed.
Aborted (core dumped)
playpen: application terminated with error code 134

[cuviper]

Updating the mangled name for the current nightly gave me this: http://is.gd/4aWIX0

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/include/llvm/Support/Casting.h:237: typename llvm::cast_retty<X, Y*>::ret_type llvm::cast(Y*) [with X = llvm::Function; Y = llvm::Value; typename llvm::cast_retty<X, Y*>::ret_type = llvm::Function*]: Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
Aborted (core dumped)
playpen: application terminated with error code 134

[steveklabnik]

tricky!

[alexcrichton]

I don't think this is necessarily a bug that we can deal with, and I'm not sure if we would really achieve anything from trying to catch this. It's basically impossible to predict our symbol names reliably and this is just dealing with various linker tricks on Linux. If you take over random symbols then it's basically very likely you'll hit memory corruption.

As a result I'm going to close this because any infrastructure we add to protect against this seems like it wouldn't be worth its weight in maintenance.