[gcc r15-9410] c++/modules: More fixes for merging DECL_MAYBE_DELETED functions

[Nathaniel Shead via Gcc-cvs]

https://gcc.gnu.org/g:f40e39515e0b7fa69bd50bad99f1f1b8c446692f

commit r15-9410-gf40e39515e0b7fa69bd50bad99f1f1b8c446692f
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date:   Fri Apr 11 07:29:11 2025 +1000

    c++/modules: More fixes for merging DECL_MAYBE_DELETED functions
    
    My change in r15-9216 broke the case where we imported an uninstantiated
    defaulted function over the top of one we had already finished.  This
    patch ensures that we don't error for mismatches in this case.
    
    gcc/cp/ChangeLog:
    
            * module.cc (trees_in::is_matching_decl): Don't check for
            mismatches when importing a DECL_MAYBE_DELETED function over one
            that's already finished.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/noexcept-4_a.H: New test.
            * g++.dg/modules/noexcept-4_b.C: New test.
    
    Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
    Reviewed-by: Jason Merrill <ja...@redhat.com>

Diff:
---
 gcc/cp/module.cc                            |  5 ++++-
 gcc/testsuite/g++.dg/modules/noexcept-4_a.H |  6 ++++++
 gcc/testsuite/g++.dg/modules/noexcept-4_b.C | 18 ++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 8efa18baff1d..5ff5c462e79c 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -12164,7 +12164,8 @@ trees_in::is_matching_decl (tree existing, tree decl, 
bool is_typedef)
                }
            }
        }
-      else if (!DEFERRED_NOEXCEPT_SPEC_P (d_spec)
+      else if (!DECL_MAYBE_DELETED (d_inner)
+              && !DEFERRED_NOEXCEPT_SPEC_P (d_spec)
               && !comp_except_specs (d_spec, e_spec, ce_type))
        {
          mismatch_msg = G_("conflicting %<noexcept%> specifier for "
@@ -12195,6 +12196,8 @@ trees_in::is_matching_decl (tree existing, tree decl, 
bool is_typedef)
       if (DECL_MAYBE_DELETED (e_inner) && !DECL_MAYBE_DELETED (d_inner)
          && DECL_DECLARED_CONSTEXPR_P (d_inner))
        DECL_DECLARED_CONSTEXPR_P (e_inner) = true;
+      else if (!DECL_MAYBE_DELETED (e_inner) && DECL_MAYBE_DELETED (d_inner))
+       /* Nothing to do.  */;
       else if (DECL_DECLARED_CONSTEXPR_P (e_inner)
               != DECL_DECLARED_CONSTEXPR_P (d_inner))
        {
diff --git a/gcc/testsuite/g++.dg/modules/noexcept-4_a.H 
b/gcc/testsuite/g++.dg/modules/noexcept-4_a.H
new file mode 100644
index 000000000000..b888a1b93e62
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/noexcept-4_a.H
@@ -0,0 +1,6 @@
+// { dg-additional-options "-fmodule-header -std=c++20" }
+// { dg-module-cmi {} }
+
+struct exception_ptr {
+  friend bool operator==(const exception_ptr&, const exception_ptr&) = default;
+};
diff --git a/gcc/testsuite/g++.dg/modules/noexcept-4_b.C 
b/gcc/testsuite/g++.dg/modules/noexcept-4_b.C
new file mode 100644
index 000000000000..7cc55316c7cb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/noexcept-4_b.C
@@ -0,0 +1,18 @@
+// { dg-additional-options "-fmodules -std=c++20" }
+
+struct exception_ptr {
+  friend bool operator==(const exception_ptr&, const exception_ptr&) = default;
+};
+
+void enqueue() {
+  exception_ptr e;
+  e == e;
+}
+
+import "noexcept-4_a.H";
+
+int main() {
+  constexpr exception_ptr e;
+  static_assert(e == e);
+  static_assert(noexcept(e == e));
+}