GAS: Update the .section directive so that a numeric section index can be provided when the "o" flag is used.

	PR 26253
gas	* config/obj-elf.c (obj_elf_section): Accept a numeric value for
	the "o" section flag.  Interpret it as a section index.  Allow an
	index of zero.
	* doc/as.texi: Document the new behaviour.
	* NEWS: Mention the new feature.  Tidy entries.
	* testsuite/gas/elf/sh-link-zero.s: New test.
	* testsuite/gas/elf/sh-link-zero.d: New test driver.
	* testsuite/gas/elf/elf.exp: Run the new test.
	* testsuite/gas/elf/section21.l: Updated expected assembler
	output.

bfd	* elf.c (_bfd_elf_setup_sections): Do not complain about an
	sh_link value of zero when the SLF_LINK_ORDER flag is set.
	(assign_section_numbers): Likewise.

2 files changed, 35 insertions, 14 deletions

diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
index 45de821..f061ea6 100644
--- a/gas/config/obj-elf.c
+++ b/gas/config/obj-elf.c
@@ -519,8 +519,10 @@ struct section_stack
 
 static struct section_stack *section_stack;
 
+/* Return TRUE iff SEC matches the section info INF.  */
+
 static bfd_boolean
-get_section (bfd *abfd ATTRIBUTE_UNUSED, asection *sec, void *inf)
+get_section_by_match (bfd *abfd ATTRIBUTE_UNUSED, asection *sec, void *inf)
 {
   struct elf_section_match *match = (struct elf_section_match *) inf;
   const char *gname = match->group_name;
@@ -602,7 +604,7 @@ obj_elf_change_section (const char *name,
   previous_section = now_seg;
   previous_subsection = now_subseg;
 
-  old_sec = bfd_get_section_by_name_if (stdoutput, name, get_section,
+  old_sec = bfd_get_section_by_name_if (stdoutput, name, get_section_by_match,
 					(void *) match_p);
   if (old_sec)
     {
@@ -1076,6 +1078,7 @@ obj_elf_section (int push)
   int linkonce;
   subsegT new_subsection = -1;
   struct elf_section_match match;
+  unsigned long linked_to_section_index = -1UL;
 
   if (flag_mri)
     {
@@ -1215,15 +1218,24 @@ obj_elf_section (int push)
 
 	  if ((attr & SHF_LINK_ORDER) != 0 && *input_line_pointer == ',')
 	    {
-	      char c;
-	      unsigned int length;
 	      ++input_line_pointer;
 	      SKIP_WHITESPACE ();
-	      c = get_symbol_name (& beg);
-	      (void) restore_line_pointer (c);
-	      length = input_line_pointer - beg;
-	      if (length)
-		match.linked_to_symbol_name = xmemdup0 (beg, length);
+	      /* Check for a numeric section index, rather than a symbol name.  */
+	      if (ISDIGIT (* input_line_pointer))
+		{
+		  linked_to_section_index = strtoul (input_line_pointer, & input_line_pointer, 0);
+		}
+	      else
+		{
+		  char c;
+		  unsigned int length;
+
+		  c = get_symbol_name (& beg);
+		  (void) restore_line_pointer (c);
+		  length = input_line_pointer - beg;
+		  if (length)
+		    match.linked_to_symbol_name = xmemdup0 (beg, length);
+		}
 	    }
 
 	  if ((attr & SHF_GROUP) != 0 && is_clone)
@@ -1231,6 +1243,7 @@ obj_elf_section (int push)
 	      as_warn (_("? section flag ignored with G present"));
 	      is_clone = FALSE;
 	    }
+
 	  if ((attr & SHF_GROUP) != 0 && *input_line_pointer == ',')
 	    {
 	      ++input_line_pointer;
@@ -1289,6 +1302,7 @@ obj_elf_section (int push)
 	  if (*input_line_pointer == ',')
 	    {
 	      char *save = input_line_pointer;
+
 	      ++input_line_pointer;
 	      SKIP_WHITESPACE ();
 	      if (strncmp (input_line_pointer, "unique", 6) == 0)
@@ -1394,6 +1408,13 @@ obj_elf_section (int push)
     }
   elf_section_flags (now_seg) |= gnu_attr;
 
+  if (linked_to_section_index != -1UL)
+    {
+      elf_section_flags (now_seg) |= SHF_LINK_ORDER;
+      elf_section_data (now_seg)->this_hdr.sh_link = linked_to_section_index;
+      /* FIXME: Should we perform some sanity checking on the section index ?  */
+    }
+
   if (push && new_subsection != -1)
     subseg_set (now_seg, new_subsection);
 }
diff --git a/gas/config/obj-elf.h b/gas/config/obj-elf.h
index b39a1a1..4f29572 100644
--- a/gas/config/obj-elf.h
+++ b/gas/config/obj-elf.h
@@ -104,11 +104,11 @@ struct elf_obj_sy
    field.  */
 struct elf_section_match
 {
-  const char *group_name;
-  const char *linked_to_symbol_name;
-  unsigned int info;
-  unsigned int section_id;
-  flagword flags;
+  const char *   group_name;
+  const char *   linked_to_symbol_name;
+  unsigned int   info;
+  unsigned int   section_id;
+  flagword       flags;
 };
 
 #define OBJ_SYMFIELD_TYPE struct elf_obj_sy