On Thu, Oct 26, 2017 at 8:14 AM, Martin Liška <mli...@suse.cz> wrote:
> On 10/24/2017 04:39 PM, Jason Merrill wrote:
>> On 10/18/2017 08:48 AM, Martin Liška wrote:
>>> This is second patch that addresses test-suite fallout. All these tests
>>> fail because -Wreturn-type is
>>> now on by default.
>>
>>> +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C
>>> -constexpr T g(T t) { return f(t); } // { dg-error "f.int" }
>>> +constexpr T g(T t) { return f(t); } // { dg-error "f.int" "" { target
>>> c++14_only } }
>>
>>> +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-neg3.C
>>> - constexpr int bar() { return a.foo(); } // { dg-error "foo" }
>>> + constexpr int bar() { return a.foo(); } // { dg-error "foo" "" { target
>>> c++14_only } }
>>
>> Why are these changes needed? They aren't "Return a value for functions
>> with non-void return type, or change type to void, or add -Wno-return-type
>> for test."
>>
>> The rest of the patch is OK.
>>
>> Jason
>
> Hi.
>
> Sorry, I forgot to describe this change. With -std=c++11 we do:
>
> #0 massage_constexpr_body (fun=0x7ffff6955500, body=0x7ffff6813eb8) at
> ../../gcc/cp/constexpr.c:708
> #1 0x000000000087700b in explain_invalid_constexpr_fn (fun=0x7ffff6955500)
> at ../../gcc/cp/constexpr.c:896
> #2 0x00000000008799dc in cxx_eval_call_expression (ctx=0x7fffffffd150,
> t=0x7ffff6820118, lval=false, non_constant_p=0x7fffffffd1cf,
> overflow_p=0x7fffffffd1ce) at ../../gcc/cp/constexpr.c:1558
> #3 0x00000000008843fe in cxx_eval_constant_expression (ctx=0x7fffffffd150,
> t=0x7ffff6820118, lval=false, non_constant_p=0x7fffffffd1cf,
> overflow_p=0x7fffffffd1ce, jump_target=0x0) at ../../gcc/cp/constexpr.c:4069
>
> static tree
> massage_constexpr_body (tree fun, tree body)
> {
> if (DECL_CONSTRUCTOR_P (fun))
> body = build_constexpr_constructor_member_initializers
> (DECL_CONTEXT (fun), body);
> else if (cxx_dialect < cxx14)
> {
> if (TREE_CODE (body) == EH_SPEC_BLOCK)
> body = EH_SPEC_STMTS (body);
> if (TREE_CODE (body) == MUST_NOT_THROW_EXPR)
> body = TREE_OPERAND (body, 0);
> body = constexpr_fn_retval (body);
> }
> return body;
> }
>
> and we end up with error_mark_node and thus potential_constant_expression_1
> does bail out.
> That's why we don't print the later error with -std=c++11.
>
> What should we do with that?
Fix constexpr_fn_retval to ignore the call to __builtin_unreachable.
Jason
