https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92935
--- Comment #3 from pskocik at gmail dot com ---
jos...@codesourcery.com, that's interesting, but it seems like an unnecessary,
weird special case, considering that gcc already has a qualifier-dropping
mechanism that doesn't necessitate special-casing __typeof for
_Atomic-qualified types.
Casting an expression to its own type (which on gcc works for aggregates too)
doe it.
Compilable example:
#if __clang__
#define DROP_Q(X) ((void)0,X) //clang rejects the casts for aggregate
types
#else
#define DROP_Q(X) (__extension__({ (__typeof(X))(X) ; }))
//__extension__ so aggregates are accepted
//even under -pedantic
#endif
int main(void)
{
#define TEST_RVAL_CONV(Tp) \
do{ \
_Atomic const volatile Tp abar; \
const volatile Tp bar; \
__typeof(DROP_Q(bar)) noqualif_bar; \
__typeof(DROP_Q(abar)) noqualif_abar; \
_Generic(&noqualif_bar, Tp*: (void)0); \
_Generic(&noqualif_abar, Tp*: (void)0); \
}while(0)
TEST_RVAL_CONV(int);
TEST_RVAL_CONV(__typeof(int*));
typedef struct s_tp { int x; } s_tp;
TEST_RVAL_CONV(s_tp);
}
https://gcc.godbolt.org/z/UtMyxM
I think all lvalue-ness-dropping expressions (e.g., the comma operator or ?: )
ought to drop top-level qualifs too (and they do on clang), and such a
qualif-dropping operation wouldn't then be dependent on the gcc extension of
allowing casts to non-scalar types, but unfortunately, gcc does not drop
top-level qualifs in rvalue-conversions, which means the clang implementation
of the qualifier-dropping macro doesn't work on gcc.
