c++, demangle: Implement https://github.com/itanium-cxx-abi/cxx-abi/issues/148 non-proposal

The following patch attempts to implement what apparently clang++
implemented for explicit object member function mangling, but nobody
actually proposed in patch form in
https://github.com/itanium-cxx-abi/cxx-abi/issues/148

2024-01-13  Jakub Jelinek  <jakub@redhat.com>

gcc/cp/
	* mangle.cc (write_nested_name): Mangle explicit object
	member functions with H as per
	https://github.com/itanium-cxx-abi/cxx-abi/issues/148 non-proposal.
gcc/testsuite/
	* g++.dg/abi/mangle79.C: New test.
include/
	* demangle.h (enum demangle_component_type): Add
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
libiberty/
	* cp-demangle.c (FNQUAL_COMPONENT_CASE): Add case for
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_dump): Handle DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_nested_name): Parse H after N in nested name.
	(d_count_templates_scopes): Handle
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_print_mod): Likewise.
	(d_print_function_type): Likewise.
	* testsuite/demangle-expected: Add tests for explicit object
	member functions.

2 files changed, 64 insertions, 0 deletions

diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index 7d8f443..a04bc58 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -1247,6 +1247,9 @@ write_nested_name (const tree decl)
 	    write_char ('R');
 	}
     }
+  else if (DECL_DECLARES_FUNCTION_P (decl)
+	   && DECL_XOBJ_MEMBER_FUNCTION_P (decl))
+    write_char ('H');
 
   /* Is this a template instance?  */
   if (tree info = maybe_template_info (decl))
diff --git a/gcc/testsuite/g++.dg/abi/mangle79.C b/gcc/testsuite/g++.dg/abi/mangle79.C
new file mode 100644
index 0000000..99ae822
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/mangle79.C
@@ -0,0 +1,61 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+struct S {
+  static void foo (S);
+  void foo (this S);		// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+  template <int N, typename T>
+  static void bar (S, T);
+  template <int N, typename T>
+  void bar (this S, T);		// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+  static void baz (const S &);
+  void baz (this const S &);	// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+};
+
+void
+S::foo (S)
+{
+}
+
+void
+S::foo (this S)			// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+{
+}
+
+template <int N, typename T>
+void
+S::bar (S, T)
+{
+}
+
+template <int N, typename T>
+void
+S::bar (this S, T)		// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+{
+}
+
+void
+S::baz (const S &)
+{
+}
+
+void
+S::baz (this const S &)		// { dg-warning "explicit object member function only available with" "" { target c++20_down } }
+{
+}
+
+void
+qux (S *p)
+{
+  S::foo (*p);
+  p->foo ();
+  S::bar <5> (*p, 0);
+  p->bar <5> (0);
+}
+
+// { dg-final { scan-assembler "_ZN1S3fooES_" } }
+// { dg-final { scan-assembler "_ZNH1S3fooES_" } }
+// { dg-final { scan-assembler "_ZN1S3barILi5EiEEvS_T0_" } }
+// { dg-final { scan-assembler "_ZNH1S3barILi5EiEEvS_T0_" } }
+// { dg-final { scan-assembler "_ZN1S3bazERKS_" } }
+// { dg-final { scan-assembler "_ZNH1S3bazERKS_" } }