C23 Implications for C Libraries

Re:C23 Implications for C Libraries by a1369209993 on Monday November 21, 2022 @05:00PM (#33698652)

No, my 'intent' is to get:

  error: signed integer variable used as array index (-Wsigned-index)
  `int i`: should be `size_t i`
  error: comparison of signed to unsigned integer (-Wsigned-comparison)
  `i < len`: `i` has type `int`; `len` has type `size_t`

Scare quotes on "intent", because I don't write (that particular kind of) obviously broken code in the first place, but the upshot is that i and len both need to be size_t, and anything that lets the compiler obscure that is de facto bad.

Edit: previously assumed len was wrong too, but on rereading, you were implying len was already the correct type, and only i was wrong.

(Also, the word "variable" is significant; IIRC something like 5+bytecode_next_char promotes to int, but can't actually be negative[1] so shouldn't generate a warning.)

1: Assuming the compiler is configured correctly, ie char is unsigned.

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Re:C23 Implications for C Libraries by dzaima on Monday November 21, 2022 @05:46PM (#33699218)

The compiler could do those things too (-Wsign-compare is a thing; nothing for signed index though), but that won't change the existing code that uses "for (int ..." (incl. 637K C source files on github), and those warnings could be false positives too (e.g. signed indexes into lookup tables, or keeping using an int32_t after having asserted somewhere before (possibly out of the compiler's vision) that it's non-negative).

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