From: Jason Merrill <jason@redhat.com>
Date: Wed, 16 Apr 2025 20:02:09 +0000 (-0400)
Subject: c++: constexpr virtual base diagnostic
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3f0eccfd90370a7c5300f92493143c7e5a66be85;p=thirdparty%2Fgcc.git

c++: constexpr virtual base diagnostic

I thought this diagnostic could be clearer that the problem is the
combination of virtual bases and constexpr constructor, not just complain
that the class has virtual bases without context.

gcc/cp/ChangeLog:

	* constexpr.cc (is_valid_constexpr_fn): Improve diagnostic.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/constexpr-dtor16.C: Adjust diagnostic.
	* g++.dg/cpp2a/constexpr-dynamic10.C: Likewise.
---

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8a5b68c71fa..f56c5c42c82 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -307,7 +307,14 @@ is_valid_constexpr_fn (tree fun, bool complain)
     {
       ret = false;
       if (complain)
-	error ("%q#T has virtual base classes", DECL_CONTEXT (fun));
+	{
+	  if (DECL_CONSTRUCTOR_P (fun))
+	    error ("%<constexpr%> constructor in %q#T that has "
+		   "virtual base classes", DECL_CONTEXT (fun));
+	  else
+	    error ("%<constexpr%> destructor in %q#T that has "
+		   "virtual base classes", DECL_CONTEXT (fun));
+	}
     }
 
   return ret;
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor16.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor16.C
index b84aaf95b9d..99d13070571 100644
--- a/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor16.C
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor16.C
@@ -3,5 +3,5 @@
 
 struct A { virtual ~A (); };
 struct B : virtual A { constexpr ~B () {} };
-// { dg-error "'struct B' has virtual base classes" "" { target c++20 } .-1 }
+// { dg-error "'constexpr' destructor in 'struct B' that has virtual base classes" "" { target c++20 } .-1 }
 // { dg-error "'constexpr' destructors only available with" "" { target c++17_down } .-2 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic10.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic10.C
index f9f82236d15..e543ce46b51 100644
--- a/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic10.C
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic10.C
@@ -5,7 +5,7 @@
 
 struct C { virtual void a(); };
 struct B { virtual void b(); };
-struct A : virtual B, C { virtual void c(); }; // { dg-error ".struct A. has virtual base classes" }
+struct A : virtual B, C { virtual void c(); }; // { dg-error "virtual base classes" }
 
 constexpr A a; // { dg-error "call" }