Idiom exclusion is really so important

Posted Nov 13, 2024 11:09 UTC (Wed) by intelfx (subscriber, #130118)
In reply to: Idiom exclusion is really so important by pm215
Parent article: Progress on toolchain security features

> But I'll absolutely take "looks like a function call and has 'add' as a word rather than '+' as a symbol, but is extremely obviously doing an overflow check" over "has '+' in the expression but is ridiculously opaque about what it is actually doing"

Who was saying anything about being opaque?

I just proposed a `__builtin_overflows(expr)` thing which makes it equally obvious that it is a test for overflow. **And** that it is an arithmetic expression.

All those builtins disguising arithmetic operations as function calls — no. Just no. The arithmetics are infix for a reason. This is C, not some kind of a Lisp or a reverse Forth.

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Idiom exclusion is really so important

Posted Nov 13, 2024 11:20 UTC (Wed) by pm215 (subscriber, #98099) [Link]

You seemed to me to be proposing that until this suggestion of yours is implemented in compilers we should continue to open-code "if (x + y < x)". That open-coding is what I am describing as opaque.

Your idea is clearly nicer than the existing builtins, but we don't have it yet and in the best case won't have it widely available for years, so the question of what is most legible and least bug prone given current compiler facilities still matters, I think.