From 4f9401d1a802325e5dfa2db841945e1a9c59a980 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Tue, 23 Apr 2024 14:01:22 -0400 Subject: [PATCH] c++/modules: deduced return type merging [PR114795] When merging an imported function template specialization with an existing one, if the existing one has an undeduced return type and the imported one's is already deduced, we need to propagate the deduced type since once we install the imported definition we won't get a chance to deduce it by normal means. So this patch makes is_matching_decl propagate the deduced return type alongside our propagation of the exception specification. Another option would be to propagate it later when installing the imported definition from read_function_def, but it seems preferable to do it sooner rather than later. PR c++/114795 gcc/cp/ChangeLog: * module.cc (trees_in::is_matching_decl): Propagate deduced function return type. gcc/testsuite/ChangeLog: * g++.dg/modules/auto-4_a.H: New test. * g++.dg/modules/auto-4_b.C: New test. Reviewed-by: Jason Merrill --- gcc/cp/module.cc | 9 +++++++++ gcc/testsuite/g++.dg/modules/auto-4_a.H | 14 ++++++++++++++ gcc/testsuite/g++.dg/modules/auto-4_b.C | 15 +++++++++++++++ 3 files changed, 38 insertions(+) create mode 100644 gcc/testsuite/g++.dg/modules/auto-4_a.H create mode 100644 gcc/testsuite/g++.dg/modules/auto-4_b.C diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc index d94d8ff4df99..c35e70b8cb8d 100644 --- a/gcc/cp/module.cc +++ b/gcc/cp/module.cc @@ -11537,6 +11537,15 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef) else if (!DEFERRED_NOEXCEPT_SPEC_P (d_spec) && !comp_except_specs (d_spec, e_spec, ce_type)) goto mismatch; + + /* Similarly if EXISTING has an undeduced return type, but DECL's + is already deduced. */ + if (undeduced_auto_decl (existing) && !undeduced_auto_decl (decl)) + { + dump (dumper::MERGE) + && dump ("Propagating deduced return type to %N", existing); + TREE_TYPE (existing) = change_return_type (TREE_TYPE (d_type), e_type); + } } else if (is_typedef) { diff --git a/gcc/testsuite/g++.dg/modules/auto-4_a.H b/gcc/testsuite/g++.dg/modules/auto-4_a.H new file mode 100644 index 000000000000..0f7cd262dfa7 --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/auto-4_a.H @@ -0,0 +1,14 @@ +// PR c++/114795 +// { dg-additional-options "-fmodule-header" } +// { dg-module-cmi {} } + +template +struct A { + auto f() { return T(); } +}; + +template +void g() { + A a; + a.f(); +} diff --git a/gcc/testsuite/g++.dg/modules/auto-4_b.C b/gcc/testsuite/g++.dg/modules/auto-4_b.C new file mode 100644 index 000000000000..378684ef6d01 --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/auto-4_b.C @@ -0,0 +1,15 @@ +// PR c++/114795 +// { dg-additional-options "-fmodules-ts -fno-module-lazy" } + +template +struct A { + auto f() { return T(); } +}; + +A a; + +import "auto-4_a.H"; + +int main() { + g(); // { dg-bogus "before deduction of 'auto'" "" { target *-*-* } 0 } +} -- 2.47.2