Array comparisons don't work on AVR - memcmp should return a c_int

[supersurviveur]

Comparing two arrays when targeting AVR doesn't work as expected :

[0u8; 5] == [0u8; 5]

returns false.

It seems to be the same issue as #78022, memcmp returns an i32 in compiler_builtins while it's an i16 for instance on AVR.

rust/library/compiler-builtins/compiler-builtins/src/mem/mod.rs

Lines 46 to 49 in bf5e6cc

	#[mem_builtin]
	pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
	impls::compare_bytes(s1, s2, n)
	}

Meta

rustc --version --verbose:

rustc 1.90.0-nightly (855e0fe46 2025-07-11)
binary: rustc
commit-hash: 855e0fe46e68d94e9f6147531b75ac2d488c548e
commit-date: 2025-07-11
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.7

[Noratrieb]

@Patryk27

[tgross35]

Yeah this and related functions (compare_bytes) should return a c_int rather than i32. This is an easy fix if you are interested in putting up a PR, but do it in rust-lang/compiler-builtins rather than rust-lang/rust.