https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118542
Bug ID: 118542
Summary: Split -Wexpansion-to-defined for function vs. object
like macros
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: dangelog at gmail dot com
Target Milestone: ---
-Wexpansion-to-defined is currently enabled by -Wextra (or -pedantic).
While there is implementation divergence when expanding object-like macros
(notably, GCC/Clang vs. MSVC without the new preprocessor), there actually
isn't when expanding function-like macros. Usages like
#define HAS(X) (defined(PLATFORM_HAS_ ## X) && (PLATFORM_HAS ## X))
are pretty common and reasonable (cf PR49928):
https://gcc.godbolt.org/z/ajceb67rP
For this reason, Clang's -Wexpansion-to-defined has two different severities:
* it's *always* active for object-like macros (dangerous in portable code);
* it's behind -Weverything / -pedantic for function-like macros (not even
-Wextra).
Would it be reasonable for GCC to do something along the same lines? (Or, even
better, to split the warning, so that one can decide to raise/error on
object-like macros, and suppress it for function-like.)
