--gc-sections with groups and start/stop syms

The testcases added here show situations where synthesized start/stop
symbols don't cause their associated input sections to be marked.
Fixed with the elflink.c and ldlang.c changes.

bfd/
	PR 27500
	* elflink.c (_bfd_elf_gc_mark_rsec): Do special start/stop
	processing not when start/stop symbol section is unmarked but
	on first time a start/stop symbol is processed.
ld/
	* ldlang.c (insert_undefined): Don't mark symbols here.
	(lang_mark_undefineds): Do so here instead, new function.
	(lang_process): Call lang_mark_undefineds.
	* testsuite/ld-gc/start3.d,
	* testsuite/ld-gc/start3.s: New test.
	* testsuite/ld-gc/start4.d,
	* testsuite/ld-gc/start4.s: New test.
	* testsuite/ld-gc/gc.exp: Run them.

1 files changed, 19 insertions, 2 deletions

diff --git a/ld/ldlang.c b/ld/ldlang.c
index a77e8fa..684e1d2 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -3986,8 +3986,6 @@ insert_undefined (const char *name)
       h->type = bfd_link_hash_undefined;
       h->u.undef.abfd = NULL;
       h->non_ir_ref_regular = TRUE;
-      if (is_elf_hash_table (link_info.hash))
-	((struct elf_link_hash_entry *) h)->mark = 1;
       bfd_link_add_undef (link_info.hash, h);
     }
 }
@@ -4005,6 +4003,23 @@ lang_place_undefineds (void)
     insert_undefined (ptr->name);
 }
 
+/* Mark -u symbols against garbage collection.  */
+
+static void
+lang_mark_undefineds (void)
+{
+  ldlang_undef_chain_list_type *ptr;
+
+  if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
+    for (ptr = ldlang_undef_chain_list_head; ptr != NULL; ptr = ptr->next)
+      {
+	struct elf_link_hash_entry *h = (struct elf_link_hash_entry *)
+	  bfd_link_hash_lookup (link_info.hash, ptr->name, FALSE, FALSE, TRUE);
+	if (h != NULL)
+	  h->mark = 1;
+      }
+}
+
 /* Structure used to build the list of symbols that the user has required
    be defined.  */
 
@@ -8116,6 +8131,8 @@ lang_process (void)
   /* Remove unreferenced sections if asked to.  */
   lang_gc_sections ();
 
+  lang_mark_undefineds ();
+
   /* Check relocations.  */
   lang_check_relocs ();