On 06/07/2016 01:42 PM, Jakub Jelinek wrote:
On Tue, Jun 07, 2016 at 03:35:28PM -0400, Jason Merrill wrote:Indeed, confirming removal of the cp/tree.c hunk doesn't affect anything in the testsuite, nor e.g. enum A { B = 1, C = 2, D = __builtin_add_overflow_p (B, C, C) }; int e[__builtin_add_overflow_p (B, C, C) + 1]; template <int N> int foo (int); void bar () { foo <__builtin_add_overflow_p (B, C, C) + 1> (0); } That said, builtin_valid_in_constant_expr_p is used in lots of spots, and in various of them I see that without the change it actually sets *non_integral_constant_expression_p = true; or something similar, but I have no idea why it still works despite of that.Ah, that's the C++98 constant expression handling, which is a lot more restricted. C++11 and up don't care about that flag.Oops, actually, it seems even the cp/tree.c hunks are significant: I've only compiled the above testcase with the default -std=c++14, with -std=c++98 without the cp/tree.c bits I get: a.C:4:7: error: ‘bool __builtin_add_overflow_p(...)’ cannot appear in a constant-expression D = __builtin_add_overflow_p (B, C, C) ^~~~~~~~~~~~~~~~~~~~~~~~ a.C:4:40: error: a function call cannot appear in a constant-expression D = __builtin_add_overflow_p (B, C, C) ^ a.C:6:45: error: array bound is not an integer constant before ‘]’ token int e[__builtin_add_overflow_p (B, C, C) + 1]; ^ a.C: In function ‘void bar()’: a.C:11:8: error: ‘bool __builtin_add_overflow_p(...)’ cannot appear in a constant-expression foo <__builtin_add_overflow_p (B, C, C) + 1> (0); ^~~~~~~~~~~~~~~~~~~~~~~~ a.C:11:41: error: a function call cannot appear in a constant-expression foo <__builtin_add_overflow_p (B, C, C) + 1> (0); ^ a.C:11:50: error: no matching function for call to ‘foo(int)’ foo <__builtin_add_overflow_p (B, C, C) + 1> (0); ^ a.C:7:22: note: candidate: template<int N> int foo(int) template <int N> int foo (int); ^~~ a.C:7:22: note: template argument deduction/substitution failed: a.C:11:50: error: template argument 1 is invalid foo <__builtin_add_overflow_p (B, C, C) + 1> (0); ^ Though, maybe it is only worth supporting the __builtin_*_overflow_p builtins for C++98 integer constant expression contexts and thus only handle there the 3 builtins instead of all the others. I guess I should add this testcase to the testsuite then.
I've also since discovered that the handling of (at least) BUILTIN_LINE is important in C++ 98 mode and if I had run the c-c++-common tests instead of just the strict C++ subset I would have seen the c-c++-common/builtin_location.c test fail with the same error. I suspect I added the other built-ins to the function to get the Clang-compatibility typed built-ins to work in C++ 98 (with the default argument). When it was decided that the Clang built-ins shouldn't change I removed the tests but not this change. Martin
