[PATCH] D69292: Proposal to add -Wtautological-compare to -Wall

[Richard Trieu via Phabricator via cfe-commits]

rtrieu added a comment.

In D69292#1747062 <https://reviews.llvm.org/D69292#1747062>, @mclow.lists wrote:

> Sorry I'm late to the party; I've been traveling for 3+ weeks.
>  I would like to be reassured that the following code will not warn:
>
>   `
>    long foo = ...; // some calculation
>    if (foo < std::numeric_limits<int>::min() || foo > std::numeric_limits<int>::max()) .....
>   
>
> This is important for systems where `sizeof(int) == sizeof(long)`


The question is whether there's a warning when a value is tautologically compared with the min or max of that value's type.  They fall under -Wtype-limits or -Wtautological-constant-in-range-compare.  Despite the "tautological" in the name, they do not fall under -Wtautological-compare.  Therefore, your example code will not get any warnings with -Wall.

I checked the clang tests and this covered by test/Sema/tautological-constant-compare.c, testing both the warnings is active only when the specific warning groups are active (the #ifdef TEST sections) and that the warnings are off for no warning flags, just -Wextra, and just -Wall.


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  https://reviews.llvm.org/D69292/new/

https://reviews.llvm.org/D69292