https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85940
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Hmm, Even clang has the same bug: https://godbolt.org/z/fszxdGrsv <source>:3:19: warning: use of GNU address-of-label extension [-Wgnu-label-as-value] return (bool()) && x; ^ <source>:3:10: error: C-style cast from 'void *' to 'bool ()' is not allowed return (bool()) && x; ^~~~~~~~~~~~~ <source>:3:22: error: use of undeclared label 'x' return (bool()) && x; ^ 1 warning and 2 errors generated. Compiler returned: 1 So what I think is happening is both GCC and clang think (bool()) is cast to a function type. This one of the areas in the C++ standard which has an ambiguity that says it should resolve to a function type and it seems like the extension gets in the way after that.
