https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80265
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2017-03-30
CC| |jakub at gcc dot gnu.org,
| |jason at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
It fails even if s1/s2/s are all const char [].
What cxx_eval_builtin_function_calls sees is after cxx_eval_constant_expression
as args[0] is
(const void *) &s1
and the middle-end obviously can't do anything with that.
While the var may have DECL_INITIAL, if it isn't const, we don't know if we can
use it, and the middle-end I think will not look at DECL_INITIAL anyway.
Furthermore, what about cases like:
constexpr int foo (char x, char y)
{
char a[10] = "abcde";
a[2] = x;
a[4] = y;
return __builtin_memcmp (a, "abAdB", 6);
}
etc.? Guess we'd need to be able to convert a CONSTRUCTOR to STRING_CST on the
fly. Furthermore, the generic folding will give us as return value say for
strstr or similar functions that return pointers into the arguments something
like STRING_CST + value, while we in the end need instead ADDR_EXPR of the
variable plus something.
So perhaps we need to handle these builtins in the C++ FE?
Jason, any thoughts on this?
