GCC

Contracts let a C++ function state what callers must guarantee and what it promises back. A violation can be ignored, observed, enforced or quick-enforced, chosen per build with no portable per-assertion switch, and the guide warns they are not input validation.

Walter Bright, who says he added contracts to Zortech C++ in the 1990s and to D later, wrote that they "just turned out to not be very useful". An embedded developer wants the opposite trade: checks on at the workstation, off on weak production CPUs.

The goal isn't the 46M-line artifact; it's the tool that produced it. The author's 'cilly' compiler probes the target C compiler with tiny witness programs instead of assuming anything beyond ANSI C, and can even compile over the network — so 'unsupported target' stops being a knock against Rust.

The thread found the genuinely useful uses. An ex-compiler developer gave a flat endorsement. Others pointed to easier Rust bootstrapping and a security trick: use crustc for Diverse Double-Compiling to check whether the official rustc has a backdoor. The skeptic's fair point: who trusts a beta transpiler on an exotic target?