Use strtab with GC and suffix merging for .strtab

This patch uses ELF strtab with GC and suffix merging support to create
ELF .strtab section.  There is some small memory overhead to use ELF
strtab:

==14928== HEAP SUMMARY:
==14928==     in use at exit: 3,276,318 bytes in 679 blocks
==14928==   total heap usage: 1,544 allocs, 865 frees, 15,259,146 bytes allocated

vs.

==14936== HEAP SUMMARY:
==14936==     in use at exit: 3,276,318 bytes in 679 blocks
==14936==   total heap usage: 1,532 allocs, 853 frees, 15,026,402 bytes allocated

when running:

./ld-new -m elf_x86_64 -o tmpdir/ld-partial.o -r ldgram.o ldlex-wrapper.o lexsup.o ldlang.o mri.o ldctor.o ldmain.o plugin.o ldwrite.o ldexp.o ldemul.o ldver.o ldmisc.o ldfile.o ldcref.o eelf_x86_64.o eelf32_x86_64.o eelf_i386.o eelf_iamcu.o ei386linux.o eelf_l1om.o eelf_k1om.o ldbuildid.o

The results are

  [32] .strtab STRTAB 0+ 3beff8 00407a 00 0 0 1

vs

  [32] .strtab STRTAB 0+ 3beff8 0041d8 00 0 0 1

It reduces the .strtab size by 350 bytes, about 2%

Saving on libc.so from glibc is much more since libc.so has many alias
symbols with the same suffix.  For x32 glibc,

 [82] .strtab STRTAB 0+ 81b348 0159e7 00 0 0 1

vs

 [82] .strtab STRTAB 0+ 81b8bc 019e72 00 0 0 1

It reduces the .strtab size by 17547 bytes, about 16%.

bfd/

	PR gas/18451
	* elf-bfd.h (elf_sym_strtab): New.
	(elf_link_hash_table): Add strtabcount, strtabsize and
	strtab.
	(_bfd_elf_stringtab_init): Removed.
	* elf.c (_bfd_elf_stringtab_init): Removed.
	(_bfd_elf_compute_section_file_positions): Replace
	bfd_strtab_hash/_bfd_elf_stringtab_init/_bfd_stringtab_free/
	_bfd_stringtab_size with
	elf_strtab_hash/_bfd_elf_strtab_init/_bfd_elf_strtab_free/
	_bfd_elf_strtab_size.  Use _bfd_elf_strtab_add,
	_bfd_elf_strtab_finalize and _bfd_elf_strtab_offset to get
	st_name.
	(swap_out_syms): Likewise.
	* elflink.c (elf_final_link_info): Replace bfd_strtab_hash
	with elf_strtab_hash.  Remove symbuf, symbuf_count,
	symbuf_size and shndxbuf_size.
	(elf_link_flush_output_syms): Removed.
	(elf_link_output_sym): Renamed to ...
	(elf_link_output_symstrtab): This.  Replace _bfd_stringtab_add
	with _bfd_elf_strtab_add.  Don't flush symbols to the file nor
	swap out symbols.
	(elf_link_swap_symbols_out): New.
	(elf_link_output_extsym): Replace elf_link_output_sym with
	elf_link_output_symstrtab.
	(elf_link_input_bfd): Likewise.
	(elf_final_link_free): Replace _bfd_stringtab_free with
	_bfd_elf_strtab_free.  Remove symbuf.
	(bfd_elf_final_link): Replace _bfd_elf_stringtab_init with
	_bfd_elf_strtab_init.  Don't set symbuf, symbuf_count,
	symbuf_size nor shndxbuf_size.  Initialize strtabsize and
	strtab.  Initialize symshndxbuf to -1 when number of sections
	>= 64K.  Replace elf_link_output_sym/elf_link_output_sym with
	elf_link_output_symstrtab/elf_link_output_symstrtab. Don't
	call elf_link_flush_output_syms.  Call _bfd_elf_strtab_finalize
	and elf_link_swap_symbols_out.  Replace _bfd_stringtab_size
	and _bfd_stringtab_emit with _bfd_elf_strtab_size and
	_bfd_elf_strtab_emit.

gas/testsuite/

	PR gas/18451
	* gas/elf/elf.exp: Run strtab.
	* gas/elf/strtab.d: New file.
	* gas/elf/strtab.s: Likewise.

ld/testsuite/

	PR gas/18451
	* ld-elf/strtab.d: New file.
	* ld-elf/strtab.s: Likewise.

11 files changed, 324 insertions, 174 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 97c1431361b..321d86f0af4 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,44 @@
+2015-06-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR gas/18451
+	* elf-bfd.h (elf_sym_strtab): New.
+	(elf_link_hash_table): Add strtabcount, strtabsize and
+	strtab.
+	(_bfd_elf_stringtab_init): Removed.
+	* elf.c (_bfd_elf_stringtab_init): Removed.
+	(_bfd_elf_compute_section_file_positions): Replace
+	bfd_strtab_hash/_bfd_elf_stringtab_init/_bfd_stringtab_free/
+	_bfd_stringtab_size with
+	elf_strtab_hash/_bfd_elf_strtab_init/_bfd_elf_strtab_free/
+	_bfd_elf_strtab_size.  Use _bfd_elf_strtab_add,
+	_bfd_elf_strtab_finalize and _bfd_elf_strtab_offset to get
+	st_name.
+	(swap_out_syms): Likewise.
+	* elflink.c (elf_final_link_info): Replace bfd_strtab_hash
+	with elf_strtab_hash.  Remove symbuf, symbuf_count,
+	symbuf_size and shndxbuf_size.
+	(elf_link_flush_output_syms): Removed.
+	(elf_link_output_sym): Renamed to ...
+	(elf_link_output_symstrtab): This.  Replace _bfd_stringtab_add
+	with _bfd_elf_strtab_add.  Don't flush symbols to the file nor
+	swap out symbols.
+	(elf_link_swap_symbols_out): New.
+	(elf_link_output_extsym): Replace elf_link_output_sym with
+	elf_link_output_symstrtab.
+	(elf_link_input_bfd): Likewise.
+	(elf_final_link_free): Replace _bfd_stringtab_free with
+	_bfd_elf_strtab_free.  Remove symbuf.
+	(bfd_elf_final_link): Replace _bfd_elf_stringtab_init with
+	_bfd_elf_strtab_init.  Don't set symbuf, symbuf_count,
+	symbuf_size nor shndxbuf_size.  Initialize strtabsize and
+	strtab.  Initialize symshndxbuf to -1 when number of sections
+	>= 64K.  Replace elf_link_output_sym/elf_link_output_sym with
+	elf_link_output_symstrtab/elf_link_output_symstrtab. Don't
+	call elf_link_flush_output_syms.  Call _bfd_elf_strtab_finalize
+	and elf_link_swap_symbols_out.  Replace _bfd_stringtab_size
+	and _bfd_stringtab_emit with _bfd_elf_strtab_size and
+	_bfd_elf_strtab_emit.
+
 2015-06-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* elf64-x86-64.c (elf_x86_64_convert_mov_to_lea): Silence older
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 1127b7ebc12..06a3883086e 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -469,6 +469,13 @@ enum elf_target_id
   GENERIC_ELF_DATA
 };
 
+struct elf_sym_strtab
+{
+  Elf_Internal_Sym sym;
+  unsigned long dest_index;
+  unsigned long destshndx_index;
+};
+
 /* ELF linker hash table.  */
 
 struct elf_link_hash_table
@@ -512,6 +519,17 @@ struct elf_link_hash_table
      section.  */
   struct elf_strtab_hash *dynstr;
 
+  /* The number of symbol strings found in the link which must be put
+     into the .strtab section.  */
+  bfd_size_type strtabcount;
+
+  /* The array size of the symbol string table, which becomes the
+     .strtab section.  */
+  bfd_size_type strtabsize;
+
+  /* The array of strings, which becomes the .strtab section.  */
+  struct elf_sym_strtab *strtab;
+
   /* The number of buckets in the hash table in the .hash section.
      This is based on the number of dynamic symbols.  */
   bfd_size_type bucketcount;
@@ -1980,8 +1998,6 @@ extern Elf_Internal_Sym *bfd_sym_from_r_symndx
   (struct sym_cache *, bfd *, unsigned long);
 extern asection *bfd_section_from_elf_index
   (bfd *, unsigned int);
-extern struct bfd_strtab_hash *_bfd_elf_stringtab_init
-  (void);
 
 extern struct elf_strtab_hash * _bfd_elf_strtab_init
   (void);
diff --git a/bfd/elf.c b/bfd/elf.c
index 47638f4b55f..4020961a6a6 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -51,7 +51,7 @@ SECTION
 static int elf_sort_sections (const void *, const void *);
 static bfd_boolean assign_file_positions_except_relocs (bfd *, struct bfd_link_info *);
 static bfd_boolean prep_headers (bfd *);
-static bfd_boolean swap_out_syms (bfd *, struct bfd_strtab_hash **, int) ;
+static bfd_boolean swap_out_syms (bfd *, struct elf_strtab_hash **, int) ;
 static bfd_boolean elf_read_notes (bfd *, file_ptr, bfd_size_type) ;
 static bfd_boolean elf_parse_notes (bfd *abfd, char *buf, size_t size,
 				    file_ptr offset);
@@ -1610,29 +1610,6 @@ bfd_elf_print_symbol (bfd *abfd,
       break;
     }
 }
-
-/* Allocate an ELF string table--force the first byte to be zero.  */
-
-struct bfd_strtab_hash *
-_bfd_elf_stringtab_init (void)
-{
-  struct bfd_strtab_hash *ret;
-
-  ret = _bfd_stringtab_init ();
-  if (ret != NULL)
-    {
-      bfd_size_type loc;
-
-      loc = _bfd_stringtab_add (ret, "", TRUE, FALSE);
-      BFD_ASSERT (loc == 0 || loc == (bfd_size_type) -1);
-      if (loc == (bfd_size_type) -1)
-	{
-	  _bfd_stringtab_free (ret);
-	  ret = NULL;
-	}
-    }
-  return ret;
-}
 
 /* ELF .o/exec file reading */
 
@@ -3742,7 +3719,7 @@ _bfd_elf_compute_section_file_positions (bfd *abfd,
   const struct elf_backend_data *bed = get_elf_backend_data (abfd);
   struct fake_section_arg fsargs;
   bfd_boolean failed;
-  struct bfd_strtab_hash *strtab = NULL;
+  struct elf_strtab_hash *strtab = NULL;
   Elf_Internal_Shdr *shstrtab_hdr;
   bfd_boolean need_symtab;
 
@@ -3827,9 +3804,9 @@ _bfd_elf_compute_section_file_positions (bfd *abfd,
       /* Now that we know where the .strtab section goes, write it
 	 out.  */
       if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0
-	  || ! _bfd_stringtab_emit (abfd, strtab))
+	  || ! _bfd_elf_strtab_emit (abfd, strtab))
 	return FALSE;
-      _bfd_stringtab_free (strtab);
+      _bfd_elf_strtab_free (strtab);
     }
 
   abfd->output_has_begun = TRUE;
@@ -7065,18 +7042,21 @@ _bfd_elf_copy_private_symbol_data (bfd *ibfd,
 
 static bfd_boolean
 swap_out_syms (bfd *abfd,
-	       struct bfd_strtab_hash **sttp,
+	       struct elf_strtab_hash **sttp,
 	       int relocatable_p)
 {
   const struct elf_backend_data *bed;
   int symcount;
   asymbol **syms;
-  struct bfd_strtab_hash *stt;
+  struct elf_strtab_hash *stt;
   Elf_Internal_Shdr *symtab_hdr;
   Elf_Internal_Shdr *symtab_shndx_hdr;
   Elf_Internal_Shdr *symstrtab_hdr;
+  struct elf_sym_strtab *symstrtab;
   bfd_byte *outbound_syms;
   bfd_byte *outbound_shndx;
+  unsigned long outbound_syms_index;
+  unsigned long outbound_shndx_index;
   int idx;
   unsigned int num_locals;
   bfd_size_type amt;
@@ -7086,7 +7066,7 @@ swap_out_syms (bfd *abfd,
     return FALSE;
 
   /* Dump out the symtabs.  */
-  stt = _bfd_elf_stringtab_init ();
+  stt = _bfd_elf_strtab_init ();
   if (stt == NULL)
     return FALSE;
 
@@ -7102,16 +7082,29 @@ swap_out_syms (bfd *abfd,
   symstrtab_hdr = &elf_tdata (abfd)->strtab_hdr;
   symstrtab_hdr->sh_type = SHT_STRTAB;
 
+  /* Allocate buffer to swap out the .strtab section.  */
+  symstrtab = (struct elf_sym_strtab *) bfd_malloc ((symcount + 1)
+						    * sizeof (*symstrtab));
+  if (symstrtab == NULL)
+    {
+      _bfd_elf_strtab_free (stt);
+      return FALSE;
+    }
+
   outbound_syms = (bfd_byte *) bfd_alloc2 (abfd, 1 + symcount,
                                            bed->s->sizeof_sym);
   if (outbound_syms == NULL)
     {
-      _bfd_stringtab_free (stt);
+error_return:
+      _bfd_elf_strtab_free (stt);
+      free (symstrtab);
       return FALSE;
     }
   symtab_hdr->contents = outbound_syms;
+  outbound_syms_index = 0;
 
   outbound_shndx = NULL;
+  outbound_shndx_index = 0;
   symtab_shndx_hdr = &elf_tdata (abfd)->symtab_shndx_hdr;
   if (symtab_shndx_hdr->sh_name != 0)
     {
@@ -7119,10 +7112,7 @@ swap_out_syms (bfd *abfd,
       outbound_shndx =  (bfd_byte *)
           bfd_zalloc2 (abfd, 1 + symcount, sizeof (Elf_External_Sym_Shndx));
       if (outbound_shndx == NULL)
-	{
-	  _bfd_stringtab_free (stt);
-	  return FALSE;
-	}
+	goto error_return;
 
       symtab_shndx_hdr->contents = outbound_shndx;
       symtab_shndx_hdr->sh_type = SHT_SYMTAB_SHNDX;
@@ -7142,10 +7132,12 @@ swap_out_syms (bfd *abfd,
     sym.st_other = 0;
     sym.st_shndx = SHN_UNDEF;
     sym.st_target_internal = 0;
-    bed->s->swap_symbol_out (abfd, &sym, outbound_syms, outbound_shndx);
-    outbound_syms += bed->s->sizeof_sym;
+    symstrtab[0].sym = sym;
+    symstrtab[0].dest_index = outbound_syms_index;
+    symstrtab[0].destshndx_index = outbound_shndx_index;
+    outbound_syms_index++;
     if (outbound_shndx != NULL)
-      outbound_shndx += sizeof (Elf_External_Sym_Shndx);
+      outbound_shndx_index++;
   }
 
   name_local_sections
@@ -7153,7 +7145,7 @@ swap_out_syms (bfd *abfd,
        && bed->elf_backend_name_local_section_symbols (abfd));
 
   syms = bfd_get_outsymbols (abfd);
-  for (idx = 0; idx < symcount; idx++)
+  for (idx = 0; idx < symcount;)
     {
       Elf_Internal_Sym sym;
       bfd_vma value = syms[idx]->value;
@@ -7165,18 +7157,17 @@ swap_out_syms (bfd *abfd,
 	  && (flags & (BSF_SECTION_SYM | BSF_GLOBAL)) == BSF_SECTION_SYM)
 	{
 	  /* Local section symbols have no name.  */
-	  sym.st_name = 0;
+	  sym.st_name = (unsigned long) -1;
 	}
       else
 	{
-	  sym.st_name = (unsigned long) _bfd_stringtab_add (stt,
-							    syms[idx]->name,
-							    TRUE, FALSE);
+	  /* Call _bfd_elf_strtab_offset after _bfd_elf_strtab_finalize
+	     to get the final offset for st_name.  */
+	  sym.st_name
+	    = (unsigned long) _bfd_elf_strtab_add (stt, syms[idx]->name,
+						   FALSE);
 	  if (sym.st_name == (unsigned long) -1)
-	    {
-	      _bfd_stringtab_free (stt);
-	      return FALSE;
-	    }
+	    goto error_return;
 	}
 
       type_ptr = elf_symbol_from (abfd, syms[idx]);
@@ -7266,8 +7257,7 @@ Unable to find equivalent output section for symbol '%s' from section '%s'"),
 					  syms[idx]->name ? syms[idx]->name : "<Local sym>",
 					  sec->name);
 		      bfd_set_error (bfd_error_invalid_operation);
-		      _bfd_stringtab_free (stt);
-		      return FALSE;
+		      goto error_return;
 		    }
 
 		  shndx = _bfd_elf_section_from_bfd_section (abfd, sec2);
@@ -7353,14 +7343,40 @@ Unable to find equivalent output section for symbol '%s' from section '%s'"),
 	  sym.st_target_internal = 0;
 	}
 
-      bed->s->swap_symbol_out (abfd, &sym, outbound_syms, outbound_shndx);
-      outbound_syms += bed->s->sizeof_sym;
+      idx++;
+      symstrtab[idx].sym = sym;
+      symstrtab[idx].dest_index = outbound_syms_index;
+      symstrtab[idx].destshndx_index = outbound_shndx_index;
+
+      outbound_syms_index++;
       if (outbound_shndx != NULL)
-	outbound_shndx += sizeof (Elf_External_Sym_Shndx);
+	outbound_shndx_index++;
     }
 
+  /* Finalize the .strtab section.  */
+  _bfd_elf_strtab_finalize (stt);
+
+  /* Swap out the .strtab section.  */
+  for (idx = 0; idx <= symcount; idx++)
+    {
+      struct elf_sym_strtab *elfsym = &symstrtab[idx];
+      if (elfsym->sym.st_name == (unsigned long) -1)
+	elfsym->sym.st_name = 0;
+      else
+	elfsym->sym.st_name = _bfd_elf_strtab_offset (stt,
+						      elfsym->sym.st_name);
+      bed->s->swap_symbol_out (abfd, &elfsym->sym,
+			       (outbound_syms
+				+ (elfsym->dest_index
+				   * bed->s->sizeof_sym)),
+			       (outbound_shndx
+				+ (elfsym->destshndx_index
+				   * sizeof (Elf_External_Sym_Shndx))));
+    }
+  free (symstrtab);
+
   *sttp = stt;
-  symstrtab_hdr->sh_size = _bfd_stringtab_size (stt);
+  symstrtab_hdr->sh_size = _bfd_elf_strtab_size (stt);
   symstrtab_hdr->sh_type = SHT_STRTAB;
 
   symstrtab_hdr->sh_flags = 0;
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 95209061313..1c0861ba3aa 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -7444,7 +7444,7 @@ struct elf_final_link_info
   /* Output BFD.  */
   bfd *output_bfd;
   /* Symbol string table.  */
-  struct bfd_strtab_hash *symstrtab;
+  struct elf_strtab_hash *symstrtab;
   /* .dynsym section.  */
   asection *dynsym_sec;
   /* .hash section.  */
@@ -7471,16 +7471,8 @@ struct elf_final_link_info
   /* Array large enough to hold a section pointer for each local
      symbol of any input BFD.  */
   asection **sections;
-  /* Buffer to hold swapped out symbols.  */
-  bfd_byte *symbuf;
-  /* And one for symbol section indices.  */
+  /* Buffer for SHT_SYMTAB_SHNDX section.  */
   Elf_External_Sym_Shndx *symshndxbuf;
-  /* Number of swapped out symbols in buffer.  */
-  size_t symbuf_count;
-  /* Number of symbols which fit in symbuf.  */
-  size_t symbuf_size;
-  /* And same for symshndxbuf.  */
-  size_t shndxbuf_size;
   /* Number of STT_FILE syms seen.  */
   size_t filesym_count;
 };
@@ -8570,47 +8562,21 @@ elf_link_sort_relocs (bfd *abfd, struct bfd_link_info *info, asection **psec)
   return ret;
 }
 
-/* Flush the output symbols to the file.  */
-
-static bfd_boolean
-elf_link_flush_output_syms (struct elf_final_link_info *flinfo,
-			    const struct elf_backend_data *bed)
-{
-  if (flinfo->symbuf_count > 0)
-    {
-      Elf_Internal_Shdr *hdr;
-      file_ptr pos;
-      bfd_size_type amt;
-
-      hdr = &elf_tdata (flinfo->output_bfd)->symtab_hdr;
-      pos = hdr->sh_offset + hdr->sh_size;
-      amt = flinfo->symbuf_count * bed->s->sizeof_sym;
-      if (bfd_seek (flinfo->output_bfd, pos, SEEK_SET) != 0
-	  || bfd_bwrite (flinfo->symbuf, amt, flinfo->output_bfd) != amt)
-	return FALSE;
-
-      hdr->sh_size += amt;
-      flinfo->symbuf_count = 0;
-    }
-
-  return TRUE;
-}
-
-/* Add a symbol to the output symbol table.  */
+/* Add a symbol to the output symbol string table.  */
 
 static int
-elf_link_output_sym (struct elf_final_link_info *flinfo,
-		     const char *name,
-		     Elf_Internal_Sym *elfsym,
-		     asection *input_sec,
-		     struct elf_link_hash_entry *h)
-{
-  bfd_byte *dest;
-  Elf_External_Sym_Shndx *destshndx;
+elf_link_output_symstrtab (struct elf_final_link_info *flinfo,
+			   const char *name,
+			   Elf_Internal_Sym *elfsym,
+			   asection *input_sec,
+			   struct elf_link_hash_entry *h)
+{
   int (*output_symbol_hook)
     (struct bfd_link_info *, const char *, Elf_Internal_Sym *, asection *,
      struct elf_link_hash_entry *);
+  struct elf_link_hash_table *hash_table;
   const struct elf_backend_data *bed;
+  bfd_size_type strtabsize;
 
   BFD_ASSERT (elf_onesymtab (flinfo->output_bfd));
 
@@ -8623,49 +8589,119 @@ elf_link_output_sym (struct elf_final_link_info *flinfo,
 	return ret;
     }
 
-  if (name == NULL || *name == '\0')
-    elfsym->st_name = 0;
-  else if (input_sec->flags & SEC_EXCLUDE)
-    elfsym->st_name = 0;
+  if (name == NULL
+      || *name == '\0'
+      || (input_sec->flags & SEC_EXCLUDE))
+    elfsym->st_name = (unsigned long) -1;
   else
     {
-      elfsym->st_name = (unsigned long) _bfd_stringtab_add (flinfo->symstrtab,
-							    name, TRUE, FALSE);
+      /* Call _bfd_elf_strtab_offset after _bfd_elf_strtab_finalize
+	 to get the final offset for st_name.  */
+      elfsym->st_name
+	= (unsigned long) _bfd_elf_strtab_add (flinfo->symstrtab,
+					       name, FALSE);
       if (elfsym->st_name == (unsigned long) -1)
 	return 0;
     }
 
-  if (flinfo->symbuf_count >= flinfo->symbuf_size)
+  hash_table = elf_hash_table (flinfo->info);
+  strtabsize = hash_table->strtabsize;
+  if (strtabsize <= hash_table->strtabcount)
     {
-      if (! elf_link_flush_output_syms (flinfo, bed))
+      strtabsize += strtabsize;
+      hash_table->strtabsize = strtabsize;
+      strtabsize *= sizeof (*hash_table->strtab);
+      hash_table->strtab
+	= (struct elf_sym_strtab *) bfd_realloc (hash_table->strtab,
+						 strtabsize);
+      if (hash_table->strtab == NULL)
 	return 0;
     }
+  hash_table->strtab[hash_table->strtabcount].sym = *elfsym;
+  hash_table->strtab[hash_table->strtabcount].dest_index
+    = hash_table->strtabcount;
+  hash_table->strtab[hash_table->strtabcount].destshndx_index
+    = flinfo->symshndxbuf ? bfd_get_symcount (flinfo->output_bfd) : 0;
+
+  bfd_get_symcount (flinfo->output_bfd) += 1;
+  hash_table->strtabcount += 1;
+
+  return 1;
+}
+
+/* Swap symbols out to the symbol table and flush the output symbols to
+   the file.  */
 
-  dest = flinfo->symbuf + flinfo->symbuf_count * bed->s->sizeof_sym;
-  destshndx = flinfo->symshndxbuf;
-  if (destshndx != NULL)
+static bfd_boolean
+elf_link_swap_symbols_out (struct elf_final_link_info *flinfo)
+{
+  struct elf_link_hash_table *hash_table = elf_hash_table (flinfo->info);
+  bfd_size_type amt, i;
+  const struct elf_backend_data *bed;
+  bfd_byte *symbuf;
+  Elf_Internal_Shdr *hdr;
+  file_ptr pos;
+  bfd_boolean ret;
+
+  if (!hash_table->strtabcount)
+    return TRUE;
+
+  BFD_ASSERT (elf_onesymtab (flinfo->output_bfd));
+
+  bed = get_elf_backend_data (flinfo->output_bfd);
+
+  amt = bed->s->sizeof_sym * hash_table->strtabcount;
+  symbuf = (bfd_byte *) bfd_malloc (amt);
+  if (symbuf == NULL)
+    return FALSE;
+  
+  if (flinfo->symshndxbuf)
     {
-      if (bfd_get_symcount (flinfo->output_bfd) >= flinfo->shndxbuf_size)
+      amt = (sizeof (Elf_External_Sym_Shndx)
+	     * (bfd_get_symcount (flinfo->output_bfd)));
+      flinfo->symshndxbuf = (Elf_External_Sym_Shndx *) bfd_zmalloc (amt);
+      if (flinfo->symshndxbuf == NULL)
 	{
-	  bfd_size_type amt;
-
-	  amt = flinfo->shndxbuf_size * sizeof (Elf_External_Sym_Shndx);
-	  destshndx = (Elf_External_Sym_Shndx *) bfd_realloc (destshndx,
-							      amt * 2);
-	  if (destshndx == NULL)
-	    return 0;
-	  flinfo->symshndxbuf = destshndx;
-	  memset ((char *) destshndx + amt, 0, amt);
-	  flinfo->shndxbuf_size *= 2;
+	  free (symbuf);
+	  return FALSE;
 	}
-      destshndx += bfd_get_symcount (flinfo->output_bfd);
     }
 
-  bed->s->swap_symbol_out (flinfo->output_bfd, elfsym, dest, destshndx);
-  flinfo->symbuf_count += 1;
-  bfd_get_symcount (flinfo->output_bfd) += 1;
+  for (i = 0; i < hash_table->strtabcount; i++)
+    {
+      struct elf_sym_strtab *elfsym = &hash_table->strtab[i];
+      if (elfsym->sym.st_name == (unsigned long) -1)
+	elfsym->sym.st_name = 0;
+      else
+	elfsym->sym.st_name
+	  = (unsigned long) _bfd_elf_strtab_offset (flinfo->symstrtab,
+						    elfsym->sym.st_name);
+      bed->s->swap_symbol_out (flinfo->output_bfd, &elfsym->sym,
+			       ((bfd_byte *) symbuf
+				+ (elfsym->dest_index
+				   * bed->s->sizeof_sym)),
+			       (flinfo->symshndxbuf
+				+ elfsym->destshndx_index));
+    }
+
+  hdr = &elf_tdata (flinfo->output_bfd)->symtab_hdr;
+  pos = hdr->sh_offset + hdr->sh_size;
+  amt = hash_table->strtabcount * bed->s->sizeof_sym;
+  if (bfd_seek (flinfo->output_bfd, pos, SEEK_SET) == 0
+      && bfd_bwrite (symbuf, amt, flinfo->output_bfd) == amt)
+    {
+      hdr->sh_size += amt;
+      ret = TRUE;
+    }
+  else
+    ret = FALSE;
 
-  return 1;
+  free (symbuf);
+
+  free (hash_table->strtab);
+  hash_table->strtab = NULL;
+
+  return ret;
 }
 
 /* Return TRUE if the dynamic symbol SYM in ABFD is supported.  */
@@ -9291,15 +9327,16 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
       memset (&fsym, 0, sizeof (fsym));
       fsym.st_info = ELF_ST_INFO (STB_LOCAL, STT_FILE);
       fsym.st_shndx = SHN_ABS;
-      if (!elf_link_output_sym (eoinfo->flinfo, NULL, &fsym,
-				bfd_und_section_ptr, NULL))
+      if (!elf_link_output_symstrtab (eoinfo->flinfo, NULL, &fsym,
+				      bfd_und_section_ptr, NULL))
 	return FALSE;
 
       eoinfo->file_sym_done = TRUE;
     }
 
   indx = bfd_get_symcount (flinfo->output_bfd);
-  ret = elf_link_output_sym (flinfo, h->root.root.string, &sym, input_sec, h);
+  ret = elf_link_output_symstrtab (flinfo, h->root.root.string, &sym,
+				   input_sec, h);
   if (ret == 0)
     {
       eoinfo->failed = TRUE;
@@ -9593,10 +9630,11 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 	  memset (&osym, 0, sizeof (osym));
 	  osym.st_info = ELF_ST_INFO (STB_LOCAL, STT_FILE);
 	  osym.st_shndx = SHN_ABS;
-	  if (!elf_link_output_sym (flinfo,
-				    (input_bfd->lto_output ? NULL
-				     : input_bfd->filename),
-				    &osym, bfd_abs_section_ptr, NULL))
+	  if (!elf_link_output_symstrtab (flinfo,
+					  (input_bfd->lto_output ? NULL
+					   : input_bfd->filename),
+					  &osym, bfd_abs_section_ptr,
+					  NULL))
 	    return FALSE;
 	}
 
@@ -9628,7 +9666,7 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 	}
 
       indx = bfd_get_symcount (output_bfd);
-      ret = elf_link_output_sym (flinfo, name, &osym, isec, NULL);
+      ret = elf_link_output_symstrtab (flinfo, name, &osym, isec, NULL);
       if (ret == 0)
 	return FALSE;
       else if (ret == 1)
@@ -9711,7 +9749,8 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 		  sym.st_value += o->output_offset;
 
 		  indx = bfd_get_symcount (output_bfd);
-		  ret = elf_link_output_sym (flinfo, name, &sym, o, NULL);
+		  ret = elf_link_output_symstrtab (flinfo, name, &sym, o,
+						   NULL);
 		  if (ret == 0)
 		    return FALSE;
 		  else if (ret == 1)
@@ -10186,8 +10225,9 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 			    }
 
 			  indx = bfd_get_symcount (output_bfd);
-			  ret = elf_link_output_sym (flinfo, name, &sym, sec,
-						     NULL);
+			  ret = elf_link_output_symstrtab (flinfo, name,
+							   &sym, sec,
+							   NULL);
 			  if (ret == 0)
 			    return FALSE;
 			  else if (ret == 1)
@@ -10634,7 +10674,7 @@ elf_final_link_free (bfd *obfd, struct elf_final_link_info *flinfo)
   asection *o;
 
   if (flinfo->symstrtab != NULL)
-    _bfd_stringtab_free (flinfo->symstrtab);
+    _bfd_elf_strtab_free (flinfo->symstrtab);
   if (flinfo->contents != NULL)
     free (flinfo->contents);
   if (flinfo->external_relocs != NULL)
@@ -10651,8 +10691,6 @@ elf_final_link_free (bfd *obfd, struct elf_final_link_info *flinfo)
     free (flinfo->indices);
   if (flinfo->sections != NULL)
     free (flinfo->sections);
-  if (flinfo->symbuf != NULL)
-    free (flinfo->symbuf);
   if (flinfo->symshndxbuf != NULL)
     free (flinfo->symshndxbuf);
   for (o = obfd->sections; o != NULL; o = o->next)
@@ -10710,7 +10748,7 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 
   flinfo.info = info;
   flinfo.output_bfd = abfd;
-  flinfo.symstrtab = _bfd_elf_stringtab_init ();
+  flinfo.symstrtab = _bfd_elf_strtab_init ();
   if (flinfo.symstrtab == NULL)
     return FALSE;
 
@@ -10737,10 +10775,7 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
   flinfo.internal_syms = NULL;
   flinfo.indices = NULL;
   flinfo.sections = NULL;
-  flinfo.symbuf = NULL;
   flinfo.symshndxbuf = NULL;
-  flinfo.symbuf_count = 0;
-  flinfo.shndxbuf_size = 0;
   flinfo.filesym_count = 0;
 
   /* The object attributes have been merged.  Remove the input
@@ -10972,27 +11007,18 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
   /* sh_offset is set just below.  */
   symtab_hdr->sh_addralign = (bfd_vma) 1 << bed->s->log_file_align;
 
-  /* Allocate a buffer to hold swapped out symbols.  This is to avoid
-     continuously seeking to the right position in the file.  */
-  if (! info->keep_memory || max_sym_count < 20)
-    flinfo.symbuf_size = 20;
-  else
-    flinfo.symbuf_size = max_sym_count;
-  amt = flinfo.symbuf_size;
-  amt *= bed->s->sizeof_sym;
-  flinfo.symbuf = (bfd_byte *) bfd_malloc (amt);
-  if (flinfo.symbuf == NULL)
+  if (max_sym_count < 20)
+    max_sym_count = 20;
+  elf_hash_table (info)->strtabsize = max_sym_count;
+  amt = max_sym_count * sizeof (struct elf_sym_strtab);
+  elf_hash_table (info)->strtab
+    = (struct elf_sym_strtab *) bfd_malloc (amt);
+  if (elf_hash_table (info)->strtab == NULL)
     goto error_return;
-  if (elf_numsections (abfd) > (SHN_LORESERVE & 0xFFFF))
-    {
-      /* Wild guess at number of output symbols.  realloc'd as needed.  */
-      amt = 2 * max_sym_count + elf_numsections (abfd) + 1000;
-      flinfo.shndxbuf_size = amt;
-      amt *= sizeof (Elf_External_Sym_Shndx);
-      flinfo.symshndxbuf = (Elf_External_Sym_Shndx *) bfd_zmalloc (amt);
-      if (flinfo.symshndxbuf == NULL)
-	goto error_return;
-    }
+  /* The real buffer will be allocated in elf_link_swap_symbols_out.  */
+  flinfo.symshndxbuf
+    = (elf_numsections (abfd) > (SHN_LORESERVE & 0xFFFF)
+       ? (Elf_External_Sym_Shndx *) -1 : NULL);
 
   if (info->strip != strip_all || emit_relocs)
     {
@@ -11012,8 +11038,8 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
       elfsym.st_other = 0;
       elfsym.st_shndx = SHN_UNDEF;
       elfsym.st_target_internal = 0;
-      if (elf_link_output_sym (&flinfo, NULL, &elfsym, bfd_und_section_ptr,
-			       NULL) != 1)
+      if (elf_link_output_symstrtab (&flinfo, NULL, &elfsym,
+				     bfd_und_section_ptr, NULL) != 1)
 	goto error_return;
 
       /* Output a symbol for each section.  We output these even if we are
@@ -11036,7 +11062,8 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 	      elfsym.st_shndx = i;
 	      if (!info->relocatable)
 		elfsym.st_value = o->vma;
-	      if (elf_link_output_sym (&flinfo, NULL, &elfsym, o, NULL) != 1)
+	      if (elf_link_output_symstrtab (&flinfo, NULL, &elfsym, o,
+					     NULL) != 1)
 		goto error_return;
 	    }
 	}
@@ -11253,7 +11280,8 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 	 struct elf_link_hash_entry *);
 
       if (! ((*bed->elf_backend_output_arch_local_syms)
-	     (abfd, info, &flinfo, (out_sym_func) elf_link_output_sym)))
+	     (abfd, info, &flinfo,
+	      (out_sym_func) elf_link_output_symstrtab)))
 	return FALSE;
     }
 
@@ -11364,12 +11392,16 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 	 struct elf_link_hash_entry *);
 
       if (! ((*bed->elf_backend_output_arch_syms)
-	     (abfd, info, &flinfo, (out_sym_func) elf_link_output_sym)))
+	     (abfd, info, &flinfo,
+	      (out_sym_func) elf_link_output_symstrtab)))
 	return FALSE;
     }
 
-  /* Flush all symbols to the file.  */
-  if (! elf_link_flush_output_syms (&flinfo, bed))
+  /* Finalize the .strtab section.  */
+  _bfd_elf_strtab_finalize (flinfo.symstrtab);
+
+  /* Swap out the .strtab section. */
+  if (!elf_link_swap_symbols_out (&flinfo))
     return FALSE;
 
   /* Now we know the size of the symtab section.  */
@@ -11402,7 +11434,7 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
       symstrtab_hdr->sh_type = SHT_STRTAB;
       symstrtab_hdr->sh_flags = 0;
       symstrtab_hdr->sh_addr = 0;
-      symstrtab_hdr->sh_size = _bfd_stringtab_size (flinfo.symstrtab);
+      symstrtab_hdr->sh_size = _bfd_elf_strtab_size (flinfo.symstrtab);
       symstrtab_hdr->sh_entsize = 0;
       symstrtab_hdr->sh_link = 0;
       symstrtab_hdr->sh_info = 0;
@@ -11414,7 +11446,7 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
       elf_next_file_pos (abfd) = off;
 
       if (bfd_seek (abfd, symstrtab_hdr->sh_offset, SEEK_SET) != 0
-	  || ! _bfd_stringtab_emit (abfd, flinfo.symstrtab))
+	  || ! _bfd_elf_strtab_emit (abfd, flinfo.symstrtab))
 	return FALSE;
     }
 
diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog
index d469d4c0b53..9db75353de9 100644
--- a/gas/testsuite/ChangeLog
+++ b/gas/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2015-06-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR gas/18451
+	* gas/elf/elf.exp: Run strtab.
+	* gas/elf/strtab.d: New file.
+	* gas/elf/strtab.s: Likewise.
+
 2015-06-22  Peter Bergner  <bergner@vnet.ibm.com>
 
 	* gas/ppc/e6500.s <sync>: Fix invalid test.
diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 47b5a21b030..ff19badefb8 100644
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -209,6 +209,8 @@ if { [is_elf_format] } then {
     run_dump_test "common1"
     run_dump_test "common2"
 
+    run_dump_test "strtab"
+
 load_lib gas-dg.exp
 dg-init
 dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/err-*.s $srcdir/$subdir/warn-*.s]] "" ""
diff --git a/gas/testsuite/gas/elf/strtab.d b/gas/testsuite/gas/elf/strtab.d
new file mode 100644
index 00000000000..c6495d7262b
--- /dev/null
+++ b/gas/testsuite/gas/elf/strtab.d
@@ -0,0 +1,7 @@
+#readelf: -W -x .strtab
+#name: .strtab section
+
+#failif
+#...
+ +0x[0-9 ]+.*\.xxxx\..*
+#...
diff --git a/gas/testsuite/gas/elf/strtab.s b/gas/testsuite/gas/elf/strtab.s
new file mode 100644
index 00000000000..931d9ef31df
--- /dev/null
+++ b/gas/testsuite/gas/elf/strtab.s
@@ -0,0 +1,8 @@
+ .text
+.globl x; x:
+.globl xx; xx:
+.globl xxx; xxx:
+.globl xxxx; xxxx:
+.globl xxxxx; xxxxx:
+.globl xxxxxx; xxxxxx:
+	.byte 0
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index 2031bc82936..abc431ec6e8 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR gas/18451
+	* ld-elf/strtab.d: New file.
+	* ld-elf/strtab.s: Likewise.
+
 2015-06-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* ld-i386/i386.exp: Run pltgot-2 for Linux targets.
diff --git a/ld/testsuite/ld-elf/strtab.d b/ld/testsuite/ld-elf/strtab.d
new file mode 100644
index 00000000000..07977087725
--- /dev/null
+++ b/ld/testsuite/ld-elf/strtab.d
@@ -0,0 +1,7 @@
+#ld: -shared
+#readelf: -W -x .strtab
+
+#failif
+#...
+ +0x[0-9 ]+.*\.xxxx\..*
+#...
diff --git a/ld/testsuite/ld-elf/strtab.s b/ld/testsuite/ld-elf/strtab.s
new file mode 100644
index 00000000000..931d9ef31df
--- /dev/null
+++ b/ld/testsuite/ld-elf/strtab.s
@@ -0,0 +1,8 @@
+ .text
+.globl x; x:
+.globl xx; xx:
+.globl xxx; xxx:
+.globl xxxx; xxxx:
+.globl xxxxx; xxxxx:
+.globl xxxxxx; xxxxxx:
+	.byte 0