c++: Fix up ICE in emit_support_tinfo_1 [PR109042]

In my recent rtti.cc change I assumed when emitting the support tinfos
that the tinfos for the fundamental types haven't been created yet.
Normally (in libsupc++.a (fundamental_type_info.o)) that is the case,
but as can be seen on the testcase, one can violate it by using typeid
etc. in the same TU and do it before ~__fundamental_type_info ()
definition.

The following patch fixes that by popping from unemitted_tinfo_decls
only in the normal case when it is there, and treating non-NULL
DECL_INITIAL on a tinfo node as indication that emit_tinfo_decl has
processed it already.

2023-03-07  Jakub Jelinek  <jakub@redhat.com>

	PR c++/109042
	* rtti.cc (emit_support_tinfo_1): Don't assert that last
	unemitted_tinfo_decls element is tinfo, instead pop from it only in
	that case.
	* decl2.cc (c_parse_final_cleanups): Don't call emit_tinfo_decl
	for unemitted_tinfO_decls which have already non-NULL DECL_INITIAL.

	* g++.dg/rtti/pr109042.C: New test.

3 files changed, 32 insertions, 3 deletions

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 31dbb4d..387e245 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -4982,7 +4982,7 @@ c_parse_final_cleanups (void)
 	 get emitted.  */
       for (i = unemitted_tinfo_decls->length ();
 	   unemitted_tinfo_decls->iterate (--i, &t);)
-	if (emit_tinfo_decl (t))
+	if (DECL_INITIAL (t) || emit_tinfo_decl (t))
 	  {
 	    reconsider = true;
 	    unemitted_tinfo_decls->unordered_remove (i);
diff --git a/gcc/cp/rtti.cc b/gcc/cp/rtti.cc
index 2a253a43..7878929 100644
--- a/gcc/cp/rtti.cc
+++ b/gcc/cp/rtti.cc
@@ -1581,10 +1581,19 @@ emit_support_tinfo_1 (tree bltn)
       /* Emit it right away if not emitted already.  */
       if (DECL_INITIAL (tinfo) == NULL_TREE)
 	{
-	  gcc_assert (unemitted_tinfo_decls->last () == tinfo);
 	  bool ok = emit_tinfo_decl (tinfo);
 	  gcc_assert (ok);
-	  unemitted_tinfo_decls->pop ();
+	  /* When compiling libsupc++.a (fundamental_type_info.o),
+	     unemitted_tinfo_decls->last () will be tinfo, so pop it
+	     from the vector as it is emitted now.  If one uses typeid
+	     etc. in the same TU as the definition of
+	     ~fundamental_type_info (), the tinfo might be emitted
+	     already earlier, in such case keep it in the vector
+	     (as otherwise we'd need to walk the whole vector) and
+	     let c_parse_final_cleanups ignore it when it will have
+	     non-NULL DECL_INITIAL.  */
+	  if (unemitted_tinfo_decls->last () == tinfo)
+	    unemitted_tinfo_decls->pop ();
 	}
     }
 }
diff --git a/gcc/testsuite/g++.dg/rtti/pr109042.C b/gcc/testsuite/g++.dg/rtti/pr109042.C
new file mode 100644
index 0000000..af448f7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/rtti/pr109042.C
@@ -0,0 +1,20 @@
+// PR c++/109042
+// { dg-do compile }
+
+namespace std { class type_info {}; }
+
+std::type_info
+foo ()
+{
+  return typeid (void);
+}
+
+namespace __cxxabiv1 {
+  struct __fundamental_type_info {
+    virtual ~__fundamental_type_info ();
+  };
+
+  __fundamental_type_info::~__fundamental_type_info ()
+  {
+  }
+}