alloc gas seginfo on notes obstack

Lots of memory used in gas should go on this obstack.  The patch also
frees all the gas obstacks on exit, which isn't a completely trivial
task.

	* subsegs.c (alloc_seginfo): New function.
	(subseg_change, subseg_get): Use it.
	(subsegs_end): New function.
	* as.h (subsegs_end): Declare.
	* output-file.c: Include subsegs.h
	(stash_frchain_obs): New function.
	(output_file_close): Save obstacks attached to output bfd before
	closing.  Call subsegs_end with the array of obstacks.

gas/as.h

@@ -476,6 +476,7 @@ void   input_scrub_end (void);
 void   new_logical_line (const char *, int);
 void   new_logical_line_flags (const char *, int, int);
 void   subsegs_begin (void);
+void   subsegs_end (struct obstack **);
 void   subseg_change (segT, int);
 segT   subseg_new (const char *, subsegT);
 segT   subseg_force_new (const char *, subsegT);

gas/output-file.c

@@ -19,6 +19,7 @@
    02110-1301, USA.  */
 
 #include "as.h"
+#include "subsegs.h"
 #include "output-file.h"
 
 #ifndef TARGET_MACH
@@ -49,24 +50,55 @@ output_file_create (const char *name)
     stdoutput->flags |= BFD_TRADITIONAL_FORMAT;
 }
 
+static void
+stash_frchain_obs (asection *sec)
+{
+  segment_info_type *info = seg_info (sec);
+  if (info)
+    {
+      struct frchain *frchp;
+      for (frchp = info->frchainP; frchp; frchp = frchp->frch_next)
+	obstack_ptr_grow (&notes, &frchp->frch_obstack);
+      info->frchainP = NULL;
+    }
+}
+
 void
 output_file_close (const char *filename)
 {
   bool res;
+  bfd *obfd = stdoutput;
+  struct obstack **obs;
+  asection *sec;
 
-  if (stdoutput == NULL)
+  if (obfd == NULL)
     return;
 
-  /* Close the bfd.  */
-  if (!flag_always_generate_output && had_errors ())
-    res = bfd_cache_close_all ();
-  else
-    res = bfd_close (stdoutput);
-
   /* Prevent an infinite loop - if the close failed we will call as_fatal
      which will call xexit() which may call this function again...  */
   stdoutput = NULL;
 
+  /* We can't free obstacks attached to the output bfd sections before
+     closing the output bfd since data in those obstacks may need to
+     be accessed, but we can't access anything in the output bfd after
+     it is closed..  */
+  for (sec = obfd->sections; sec; sec = sec->next)
+    stash_frchain_obs (sec);
+  stash_frchain_obs (reg_section);
+  stash_frchain_obs (expr_section);
+  stash_frchain_obs (bfd_abs_section_ptr);
+  stash_frchain_obs (bfd_und_section_ptr);
+  obstack_ptr_grow (&notes, NULL);
+  obs = obstack_finish (&notes);
+
+  /* Close the bfd.  */
+  if (!flag_always_generate_output && had_errors ())
+    res = bfd_cache_close_all ();
+  else
+    res = bfd_close (obfd);
+
+  subsegs_end (obs);
+
   if (! res)
     as_fatal ("%s: %s", filename, bfd_errmsg (bfd_get_error ()));
 }

gas/subsegs.c

@@ -43,7 +43,27 @@ subsegs_begin (void)
   frchain_now = NULL;		/* Warn new_subseg() that we are booting.  */
   frag_now = &dummy_frag;
 }
+
+void
+subsegs_end (struct obstack **obs)
+{
+  for (; *obs; obs++)
+    _obstack_free (*obs, NULL);
+  _obstack_free (&frchains, NULL);
+  _obstack_free (&cond_obstack, NULL);
+  _obstack_free (&notes, NULL);
+}
 
+static void
+alloc_seginfo (segT seg)
+{
+  segment_info_type *seginfo;
+
+  seginfo = obstack_alloc (&notes, sizeof (*seginfo));
+  memset (seginfo, 0, sizeof (*seginfo));
+  seginfo->bfd_section = seg;
+  bfd_set_section_userdata (seg, seginfo);
+}
 /*
  *			subseg_change()
  *
@@ -57,16 +77,11 @@ subsegs_begin (void)
 void
 subseg_change (segT seg, int subseg)
 {
-  segment_info_type *seginfo = seg_info (seg);
   now_seg = seg;
   now_subseg = subseg;
 
-  if (! seginfo)
-    {
-      seginfo = XCNEW (segment_info_type);
-      seginfo->bfd_section = seg;
-      bfd_set_section_userdata (seg, seginfo);
-    }
+  if (!seg_info (seg))
+    alloc_seginfo (seg);
 }
 
 static void
@@ -149,7 +164,6 @@ segT
 subseg_get (const char *segname, int force_new)
 {
   segT secptr;
-  segment_info_type *seginfo;
   const char *now_seg_name = now_seg ? bfd_section_name (now_seg) : 0;
 
   if (!force_new
@@ -163,13 +177,10 @@ subseg_get (const char *segname, int force_new)
   else
     secptr = bfd_make_section_anyway (stdoutput, segname);
 
-  seginfo = seg_info (secptr);
-  if (! seginfo)
+  if (!seg_info (secptr))
     {
       secptr->output_section = secptr;
-      seginfo = XCNEW (segment_info_type);
-      seginfo->bfd_section = secptr;
-      bfd_set_section_userdata (secptr, seginfo);
+      alloc_seginfo (secptr);
     }
   return secptr;
 }