[Bug c/64509] _Generic throws error in unselected generic association
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64509 Marek Polacek mpolacek at gcc dot gnu.org changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #5 from Marek Polacek mpolacek at gcc dot gnu.org --- (In reply to Martien de Jong from comment #4) BTW, I notice that ./gcc/ginclude/tgmath.h uses __builtin_classify_type __builtin_types_compatible_p __builtin_choose_expr Will it move to using _Generic() ? I think it will over time (with a proper __GNUC_PREREQ guard). Anyway, there is nothing to do for this bug, so closing.
[Bug c/64509] _Generic throws error in unselected generic association
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64509 --- Comment #4 from Martien de Jong maurits.de.jong at ericsson dot com --- I understand. What a shallow and ugly feature it is then. I think it can only usefully be employed using a preprocessor macro, yet it is part of the expression syntax. It is meant to resolve type issues, yet all variants should be type-sane. You can indeed implement something like tgmath.h with it, but only if the types can be implictly converted. BTW, I notice that ./gcc/ginclude/tgmath.h uses __builtin_classify_type __builtin_types_compatible_p __builtin_choose_expr Will it move to using _Generic() ?
[Bug c/64509] _Generic throws error in unselected generic association
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64509 Marek Polacek mpolacek at gcc dot gnu.org changed: What|Removed |Added CC||mpolacek at gcc dot gnu.org --- Comment #1 from Marek Polacek mpolacek at gcc dot gnu.org --- I think it's fine to reject that testcase. The type checking is performed when parsing while building the association expression...
[Bug c/64509] _Generic throws error in unselected generic association
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64509 --- Comment #2 from Martien de Jong maurits.de.jong at ericsson dot com --- That's just rephrasing my bugreport. The question is, should it type check while parsing an expression that may not be realized? The entire idea of switching on a type is to prevent and fix type errors, no?
[Bug c/64509] _Generic throws error in unselected generic association
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64509 --- Comment #3 from joseph at codesourcery dot com joseph at codesourcery dot com --- _Generic is intended for cases like tgmath.h, where calls to all functions are still valid for all argument types. This is a case where the expression __f(S) violates a constraint, and that constraint applies to all function calls, not just evaluated ones - this is just the same as a constraint violation inside if (0), or if (expression_that_evaluates_to_0_at_runtime). (It's also required that functions called in unevaluated generic associations are defined somewhere in the program; only sizeof and _Alignof have exemptions from that.)
