c++: Fix up push_local_extern_decl_alias error recovery [PR102642]

My recent push_local_extern_decl_alias change broke error-recovery,
do_pushdecl can return error_mark_node and set_decl_tls_model can't be
called on that.  There are other code paths that store error_mark_node
into DECL_LOCAL_DECL_ALIAS, with the intent to differentiate the cases
where we haven't yet tried to push it into the namespace scope (NULL)
and one where we have tried it but it failed (error_mark_node), but looking
around, there are other spots where we call functions or do processing
which doesn't tolerate error_mark_node.

So, the first hunk with the testcase fixes the testcase, the others
fix what I've spotted and the fix was easy to figure out (there are I think
3 other spots mainly for function multiversioning).

2021-10-20  Jakub Jelinek  <jakub@redhat.com>

	PR c++/102642
	* name-lookup.c (push_local_extern_decl_alias): Don't call
	set_decl_tls_model on error_mark_node.
	* decl.c (make_rtl_for_nonlocal_decl): Don't call
	set_user_assembler_name on error_mark_node.
	* parser.c (cp_parser_oacc_declare): Ignore DECL_LOCAL_DECL_ALIAS
	if it is error_mark_node.
	(cp_parser_omp_declare_target): Likewise.

	* g++.dg/tls/pr102642.C: New test.

4 files changed, 19 insertions, 4 deletions

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 242429d..8a45411 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7373,7 +7373,8 @@ make_rtl_for_nonlocal_decl (tree decl, tree init, const char* asmspec)
 		 This is horrible, as we're affecting a
 		 possibly-shared decl.  Again, a one-true-decl
 		 model breaks down.  */
-	      set_user_assembler_name (ns_decl, asmspec);
+	      if (ns_decl != error_mark_node)
+		set_user_assembler_name (ns_decl, asmspec);
 	}
     }
 
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index c414a10..035bcf5 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -3474,7 +3474,9 @@ push_local_extern_decl_alias (tree decl)
 	  push_nested_namespace (ns);
 	  alias = do_pushdecl (alias, /* hiding= */true);
 	  pop_nested_namespace (ns);
-	  if (VAR_P (decl) && CP_DECL_THREAD_LOCAL_P (decl))
+	  if (VAR_P (decl)
+	      && CP_DECL_THREAD_LOCAL_P (decl)
+	      && alias != error_mark_node)
 	    set_decl_tls_model (alias, DECL_TLS_MODEL (decl));
 	}
     }
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 865778e..9c7ed65 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -44437,7 +44437,8 @@ cp_parser_oacc_declare (cp_parser *parser, cp_token *pragma_tok)
 	       dependent local extern variable decls are as rare as
 	       hen's teeth.  */
 	    if (auto alias = DECL_LOCAL_DECL_ALIAS (decl))
-	      decl = alias;
+	      if (alias != error_mark_node)
+		decl = alias;
 
 	  if (OMP_CLAUSE_MAP_KIND (t) == GOMP_MAP_LINK)
 	    id = get_identifier ("omp declare target link");
@@ -45665,7 +45666,8 @@ cp_parser_omp_declare_target (cp_parser *parser, cp_token *pragma_tok)
       if (VAR_OR_FUNCTION_DECL_P (t)
 	  && DECL_LOCAL_DECL_P (t)
 	  && DECL_LANG_SPECIFIC (t)
-	  && DECL_LOCAL_DECL_ALIAS (t))
+	  && DECL_LOCAL_DECL_ALIAS (t)
+	  && DECL_LOCAL_DECL_ALIAS (t) != error_mark_node)
 	handle_omp_declare_target_clause (c, DECL_LOCAL_DECL_ALIAS (t),
 					  device_type);
     }
diff --git a/gcc/testsuite/g++.dg/tls/pr102642.C b/gcc/testsuite/g++.dg/tls/pr102642.C
new file mode 100644
index 0000000..e3236d3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tls/pr102642.C
@@ -0,0 +1,10 @@
+// PR c++/102642
+// { dg-do compile { target c++11 } }
+
+thread_local int *z;		// { dg-message "previous declaration" }
+
+void
+foo ()
+{
+  extern thread_local int z;	// { dg-error "conflicting declaration" }
+}