From 35317db051b9ce3eff7d4ad6d31de026447314f3 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Tue, 15 Dec 2020 12:10:26 -0500 Subject: [PATCH] c++: Fix return type deduction during satisfaction During satisfaction that's entered through the three-parameter version of satisfy_declaration_constraints, current_function_decl gets set to the dependent DECL_TEMPLATE_RESULT for sake of access checking. This makes the predicate in_template_function return true during satisfaction from this entrypoint, which in turn makes calls to mark_used exit early before it does its full processing. This leads to us accepting the invalid testcase below due to mark_used never attempting to deduce the return type of A::foo() and detecting failure thereof. It seems wrong for in_template_function to be true during instantiation or during satisfaction, so this patch makes in_template_function inspect the less volatile cfun->decl instead of current_function_decl. gcc/cp/ChangeLog: * pt.c (in_template_function): Inspect cfun->decl instead of current_function_decl. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-requires23.C: New test. --- gcc/cp/pt.c | 6 ++++-- gcc/testsuite/g++.dg/cpp2a/concepts-requires23.C | 9 +++++++++ 2 files changed, 13 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires23.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index e5f18d23ea0..5100954dfde 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -10805,14 +10805,16 @@ uses_template_parms (tree t) return dependent_p; } -/* Returns true iff current_function_decl is an incompletely instantiated +/* Returns true iff we're processing an incompletely instantiated function template. Useful instead of processing_template_decl because the latter is set to 0 during instantiate_non_dependent_expr. */ bool in_template_function (void) { - tree fn = current_function_decl; + /* Inspect the less volatile cfun->decl instead of current_function_decl; + the latter might get set for e.g. access checking during satisfaction. */ + tree fn = cfun ? cfun->decl : NULL_TREE; bool ret; ++processing_template_decl; ret = (fn && DECL_LANG_SPECIFIC (fn) diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires23.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires23.C new file mode 100644 index 00000000000..e109beaac4f --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires23.C @@ -0,0 +1,9 @@ +// { dg-do compile { target c++20 } } + +// Verify f's associated constraints evaluate to false due +// to return type deduction failure for A::foo(). + +template concept fooable = requires { T::foo(0); }; +template int f (); +struct A { static auto *foo(auto); }; +int a = f(); // { dg-error "no match" } -- 2.30.2