| Message ID | 20190208231853.GH2135@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | [C++] Fix std::is_constant_evaluated() in non-type template parameters (PR c++/88977) | expand |
On 2/8/19 6:18 PM, Jakub Jelinek wrote: > Hi! > > Non-type template arguments are constant-expression in the grammar and thus > manifestly constant-evaluated. > For e.g. class templates, convert_nontype_argument is called with > tf_warning_or_error and so while we called in the below spots > maybe_constant_value without manifestly_const_eval=true, there is a > if (TREE_CODE (expr) != INTEGER_CST > && !value_dependent_expression_p (expr)) > { > if (complain & tf_error) > { > int errs = errorcount, warns = warningcount + werrorcount; > if (!require_potential_constant_expression (expr)) > expr = error_mark_node; > else > expr = cxx_constant_value (expr); > later on and cxx_constant_value will do the manifestly_const_eval=true. > On the testcase below with function template, complain is tf_none and > so we only call that maybe_constant_value and not cxx_constant_value. > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for > trunk? OK.
--- gcc/cp/pt.c.jj 2019-02-05 10:04:19.038028029 +0100 +++ gcc/cp/pt.c 2019-02-08 09:46:23.370257199 +0100 @@ -6821,12 +6821,14 @@ convert_nontype_argument (tree type, tre /* Make sure we return NULL_TREE only if we have really issued an error, as described above. */ return (complain & tf_error) ? NULL_TREE : error_mark_node; - expr = maybe_constant_value (expr); + expr = maybe_constant_value (expr, NULL_TREE, + /*manifestly_const_eval=*/true); expr = convert_from_reference (expr); } else if (TYPE_PTR_OR_PTRMEM_P (type)) { - tree folded = maybe_constant_value (expr); + tree folded = maybe_constant_value (expr, NULL_TREE, + /*manifestly_const_eval=*/true); if (TYPE_PTR_P (type) ? integer_zerop (folded) : null_member_pointer_value_p (folded)) expr = folded; --- gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated7.C.jj 2019-02-08 09:53:47.255935430 +0100 +++ gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated7.C 2019-02-08 09:49:45.159957823 +0100 @@ -0,0 +1,18 @@ +// P0595R2 +// PR c++/88977 +// { dg-do compile { target c++11 } } + +namespace std { + constexpr inline bool + is_constant_evaluated () noexcept + { + return __builtin_is_constant_evaluated (); + } +} + +template<bool B> constexpr bool foo () { return B; } + +constexpr bool x = foo<std::is_constant_evaluated ()> (); +constexpr bool y = foo<__builtin_is_constant_evaluated ()> (); +static_assert (x, ""); +static_assert (y, "");
Hi! Non-type template arguments are constant-expression in the grammar and thus manifestly constant-evaluated. For e.g. class templates, convert_nontype_argument is called with tf_warning_or_error and so while we called in the below spots maybe_constant_value without manifestly_const_eval=true, there is a if (TREE_CODE (expr) != INTEGER_CST && !value_dependent_expression_p (expr)) { if (complain & tf_error) { int errs = errorcount, warns = warningcount + werrorcount; if (!require_potential_constant_expression (expr)) expr = error_mark_node; else expr = cxx_constant_value (expr); later on and cxx_constant_value will do the manifestly_const_eval=true. On the testcase below with function template, complain is tf_none and so we only call that maybe_constant_value and not cxx_constant_value. Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2019-02-08 Jakub Jelinek <jakub@redhat.com> PR c++/88977 * pt.c (convert_nontype_argument): Pass true as manifestly_const_eval to maybe_constant_value calls. * g++.dg/cpp2a/is-constant-evaluated7.C: New test. Jakub