Eliminate make_cleanup_obstack_free, introduce auto_obstack

This commit eliminates make_cleanup_obstack_free, replacing it with a
new auto_obstack type that inherits obstack to add cdtors.

These changes in the parsers may not be obvious:

 -  obstack_init (&name_obstack);
 -  make_cleanup_obstack_free (&name_obstack);
 +  name_obstack.clear ();

Here, the 'name_obstack' variable is a global.  The change means that
the obstack's contents from a previous parse will stay around until
the next parsing starts.  I.e., memory won't be reclaimed until then.
I don't think that's a problem, these objects don't really grow much
at all.

The other option I tried was to add a separate type that is like
auto_obstack but manages an external obstack, just for those cases.  I
like the current approach better as that other approach adds more
boilerplate and yet another type to learn.

gdb/ChangeLog:
2017-06-27  Pedro Alves  <palves@redhat.com>

	* c-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(c_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* c-lang.c (evaluate_subexp_c): Use auto_obstack.
	* d-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(d_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* dwarf2loc.c (fetch_const_value_from_synthetic_pointer): Use
	auto_obstack.
	* dwarf2read.c (create_addrmap_from_index)
	(dwarf2_build_psymtabs_hard)
	(update_enumeration_type_from_children): Likewise.
	* gdb_obstack.h (auto_obstack): New type.
	* go-exp.y (name_obstack): Now an auto_obstack.
	(build_packaged_name): Use auto_obstack::clear.
	(go_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* linux-tdep.c (linux_make_mappings_corefile_notes): Use
	auto_obstack.
	* printcmd.c (printf_wide_c_string, ui_printf): Use auto_obstack.
	* rust-exp.y (work_obstack): Now an auto_obstack.
	(rust_parse, rust_lex_tests): Use auto_obstack::clear instead of
	reinitializing and freeing the obstack.
	* utils.c (do_obstack_free, make_cleanup_obstack_free): Delete.
	(host_char_to_target): Use auto_obstack.
	* utils.h (make_cleanup_obstack_free): Delete declaration.
	* valprint.c (generic_emit_char, generic_printstr): Use
	auto_obstack.

gdb/ChangeLog

@@ -1,3 +1,36 @@
+2017-06-27  Pedro Alves  <palves@redhat.com>
+
+	* c-exp.y (name_obstack): Now an auto_obstack.
+	(yylex): Use auto_obstack::clear.
+	(c_parse): Use auto_obstack::clear instead of reinitializing and
+	freeing the obstack.
+	* c-lang.c (evaluate_subexp_c): Use auto_obstack.
+	* d-exp.y (name_obstack): Now an auto_obstack.
+	(yylex): Use auto_obstack::clear.
+	(d_parse): Use auto_obstack::clear instead of reinitializing and
+	freeing the obstack.
+	* dwarf2loc.c (fetch_const_value_from_synthetic_pointer): Use
+	auto_obstack.
+	* dwarf2read.c (create_addrmap_from_index)
+	(dwarf2_build_psymtabs_hard)
+	(update_enumeration_type_from_children): Likewise.
+	* gdb_obstack.h (auto_obstack): New type.
+	* go-exp.y (name_obstack): Now an auto_obstack.
+	(build_packaged_name): Use auto_obstack::clear.
+	(go_parse): Use auto_obstack::clear instead of reinitializing and
+	freeing the obstack.
+	* linux-tdep.c (linux_make_mappings_corefile_notes): Use
+	auto_obstack.
+	* printcmd.c (printf_wide_c_string, ui_printf): Use auto_obstack.
+	* rust-exp.y (work_obstack): Now an auto_obstack.
+	(rust_parse, rust_lex_tests): Use auto_obstack::clear instead of
+	reinitializing and freeing the obstack.
+	* utils.c (do_obstack_free, make_cleanup_obstack_free): Delete.
+	(host_char_to_target): Use auto_obstack.
+	* utils.h (make_cleanup_obstack_free): Delete declaration.
+	* valprint.c (generic_emit_char, generic_printstr): Use
+	auto_obstack.
+
 2017-06-27  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* darwin-nat.c (darwin_check_new_threads): Don't handle dummy

gdb/c-exp.y

@@ -2806,7 +2806,7 @@ static int popping;
 
 /* Temporary storage for c_lex; this holds symbol names as they are
    built up.  */
-static struct obstack name_obstack;
+auto_obstack name_obstack;
 
 /* Classify a NAME token.  The contents of the token are in `yylval'.
    Updates yylval and returns the new token type.  BLOCK is the block
@@ -3067,7 +3067,7 @@ yylex (void)
   current = *VEC_index (token_and_value, token_fifo, next_to_examine);
   ++next_to_examine;
 
-  obstack_free (&name_obstack, obstack_base (&name_obstack));
+  name_obstack.clear ();
   checkpoint = 0;
   if (current.token == FILENAME)
     search_block = current.value.bval;
@@ -3169,6 +3169,9 @@ c_parse (struct parser_state *par_state)
   gdb_assert (par_state != NULL);
   pstate = par_state;
 
+  /* Note that parsing (within yyparse) freely installs cleanups
+     assuming they'll be run here (below).  */
+
   back_to = make_cleanup (free_current_contents, &expression_macro_scope);
   make_cleanup_clear_parser_state (&pstate);
 
@@ -3197,8 +3200,7 @@ c_parse (struct parser_state *par_state)
 
   VEC_free (token_and_value, token_fifo);
   popping = 0;
-  obstack_init (&name_obstack);
+  name_obstack.clear ();
-  make_cleanup_obstack_free (&name_obstack);
 
   result = yyparse ();
   do_cleanups (back_to);

gdb/c-lang.c

@@ -570,15 +570,12 @@ evaluate_subexp_c (struct type *expect_type, struct expression *exp,
       {
 	int oplen, limit;
 	struct type *type;
-	struct obstack output;
-	struct cleanup *cleanup;
 	struct value *result;
 	c_string_type dest_type;
 	const char *dest_charset;
 	int satisfy_expected = 0;
 
-	obstack_init (&output);
+	auto_obstack output;
-	cleanup = make_cleanup_obstack_free (&output);
 
 	++*pos;
 	oplen = longest_to_int (exp->elts[*pos].longconst);
@@ -656,7 +653,6 @@ evaluate_subexp_c (struct type *expect_type, struct expression *exp,
 	      result = allocate_value (type);
 	    else
 	      result = value_cstring ("", 0, type);
-	    do_cleanups (cleanup);
 	    return result;
 	  }
 
@@ -702,7 +698,6 @@ evaluate_subexp_c (struct type *expect_type, struct expression *exp,
 				      obstack_object_size (&output),
 				      type);
 	  }
-	do_cleanups (cleanup);
 	return result;
       }
       break;

gdb/d-exp.y

@@ -1342,7 +1342,7 @@ static int popping;
 
 /* Temporary storage for yylex; this holds symbol names as they are
    built up.  */
-static struct obstack name_obstack;
+static auto_obstack name_obstack;
 
 /* Classify an IDENTIFIER token.  The contents of the token are in `yylval'.
    Updates yylval and returns the new token type.  BLOCK is the block
@@ -1480,7 +1480,7 @@ yylex (void)
      first try building up a name until we find the qualified module.  */
   if (current.token == UNKNOWN_NAME)
     {
-      obstack_free (&name_obstack, obstack_base (&name_obstack));
+      name_obstack.clear ();
       obstack_grow (&name_obstack, current.value.sval.ptr,
 		    current.value.sval.length);
 
@@ -1533,7 +1533,7 @@ yylex (void)
   if (current.token != TYPENAME && current.token != '.')
     goto do_pop;
 
-  obstack_free (&name_obstack, obstack_base (&name_obstack));
+  name_obstack.clear ();
   checkpoint = 0;
   if (current.token == '.')
     search_block = NULL;
@@ -1627,6 +1627,8 @@ d_parse (struct parser_state *par_state)
   gdb_assert (par_state != NULL);
   pstate = par_state;
 
+  /* Note that parsing (within yyparse) freely installs cleanups
+     assuming they're run here (below).  */
   back_to = make_cleanup (null_cleanup, NULL);
 
   scoped_restore restore_yydebug = make_scoped_restore (&yydebug,
@@ -1639,8 +1641,7 @@ d_parse (struct parser_state *par_state)
 
   VEC_free (token_and_value, token_fifo);
   popping = 0;
-  obstack_init (&name_obstack);
+  name_obstack.clear ();
-  make_cleanup_obstack_free (&name_obstack);
 
   result = yyparse ();
   do_cleanups (back_to);

gdb/dwarf2loc.c

@@ -2121,13 +2121,10 @@ fetch_const_value_from_synthetic_pointer (sect_offset die, LONGEST byte_offset,
 					  struct type *type)
 {
   struct value *result = NULL;
-  struct obstack temp_obstack;
-  struct cleanup *cleanup;
   const gdb_byte *bytes;
   LONGEST len;
 
-  obstack_init (&temp_obstack);
+  auto_obstack temp_obstack;
-  cleanup = make_cleanup_obstack_free (&temp_obstack);
   bytes = dwarf2_fetch_constant_bytes (die, per_cu, &temp_obstack, &len);
 
   if (bytes != NULL)
@@ -2144,8 +2141,6 @@ fetch_const_value_from_synthetic_pointer (sect_offset die, LONGEST byte_offset,
   else
     result = allocate_optimized_out_value (TYPE_TARGET_TYPE (type));
 
-  do_cleanups (cleanup);
-
   return result;
 }
 

gdb/dwarf2read.c

@@ -3060,13 +3060,11 @@ create_addrmap_from_index (struct objfile *objfile, struct mapped_index *index)
 {
   struct gdbarch *gdbarch = get_objfile_arch (objfile);
   const gdb_byte *iter, *end;
-  struct obstack temp_obstack;
   struct addrmap *mutable_map;
-  struct cleanup *cleanup;
   CORE_ADDR baseaddr;
 
-  obstack_init (&temp_obstack);
+  auto_obstack temp_obstack;
-  cleanup = make_cleanup_obstack_free (&temp_obstack);
+
   mutable_map = addrmap_create_mutable (&temp_obstack);
 
   iter = index->address_table;
@@ -3107,7 +3105,6 @@ create_addrmap_from_index (struct objfile *objfile, struct mapped_index *index)
 
   objfile->psymtabs_addrmap = addrmap_create_fixed (mutable_map,
 						    &objfile->objfile_obstack);
-  do_cleanups (cleanup);
 }
 
 /* The hash function for strings in the mapped index.  This is the same as
@@ -6626,7 +6623,6 @@ static void
 dwarf2_build_psymtabs_hard (struct objfile *objfile)
 {
   struct cleanup *back_to, *addrmap_cleanup;
-  struct obstack temp_obstack;
   int i;
 
   if (dwarf_read_debug)
@@ -6649,8 +6645,7 @@ dwarf2_build_psymtabs_hard (struct objfile *objfile)
 
   /* Create a temporary address map on a temporary obstack.  We later
      copy this to the final obstack.  */
-  obstack_init (&temp_obstack);
+  auto_obstack temp_obstack;
-  make_cleanup_obstack_free (&temp_obstack);
   objfile->psymtabs_addrmap = addrmap_create_mutable (&temp_obstack);
   addrmap_cleanup = make_cleanup (psymtabs_addrmap_cleanup, objfile);
 
@@ -13796,15 +13791,12 @@ update_enumeration_type_from_children (struct die_info *die,
 				       struct type *type,
 				       struct dwarf2_cu *cu)
 {
-  struct obstack obstack;
   struct die_info *child_die;
   int unsigned_enum = 1;
   int flag_enum = 1;
   ULONGEST mask = 0;
-  struct cleanup *old_chain;
 
-  obstack_init (&obstack);
+  auto_obstack obstack;
-  old_chain = make_cleanup_obstack_free (&obstack);
 
   for (child_die = die->child;
        child_die != NULL && child_die->tag;
@@ -13849,8 +13841,6 @@ update_enumeration_type_from_children (struct die_info *die,
     TYPE_UNSIGNED (type) = 1;
   if (flag_enum)
     TYPE_FLAG_ENUM (type) = 1;
-
-  do_cleanups (old_chain);
 }
 
 /* Given a DW_AT_enumeration_type die, set its type.  We do not

gdb/gdb_obstack.h

@@ -63,4 +63,19 @@ extern char *obconcat (struct obstack *obstackp, ...) ATTRIBUTE_SENTINEL;
 
 extern char *obstack_strdup (struct obstack *obstackp, const char *string);
 
+/* An obstack that frees itself on scope exit.  */
+struct auto_obstack : obstack
+{
+  auto_obstack ()
+  { obstack_init (this); }
+
+  ~auto_obstack ()
+  { obstack_free (this, NULL); }
+
+  /* Free all memory in the obstack but leave it valid for further
+     allocation.  */
+  void clear ()
+  { obstack_free (this, obstack_base (this)); }
+};
+
 #endif

gdb/go-exp.y

@@ -1297,7 +1297,7 @@ static int popping;
 
 /* Temporary storage for yylex; this holds symbol names as they are
    built up.  */
-static struct obstack name_obstack;
+static auto_obstack name_obstack;
 
 /* Build "package.name" in name_obstack.
    For convenience of the caller, the name is NUL-terminated,
@@ -1309,7 +1309,7 @@ build_packaged_name (const char *package, int package_len,
 {
   struct stoken result;
 
-  obstack_free (&name_obstack, obstack_base (&name_obstack));
+  name_obstack.clear ();
   obstack_grow (&name_obstack, package, package_len);
   obstack_grow_str (&name_obstack, ".");
   obstack_grow (&name_obstack, name, name_len);
@@ -1567,6 +1567,8 @@ go_parse (struct parser_state *par_state)
   gdb_assert (par_state != NULL);
   pstate = par_state;
 
+  /* Note that parsing (within yyparse) freely installs cleanups
+     assuming they'll be run here (below).  */
   back_to = make_cleanup (null_cleanup, NULL);
 
   scoped_restore restore_yydebug = make_scoped_restore (&yydebug,
@@ -1579,8 +1581,7 @@ go_parse (struct parser_state *par_state)
 
   VEC_free (token_and_value, token_fifo);
   popping = 0;
-  obstack_init (&name_obstack);
+  name_obstack.clear ();
-  make_cleanup_obstack_free (&name_obstack);
 
   result = yyparse ();
   do_cleanups (back_to);

gdb/linux-tdep.c

@@ -1506,16 +1506,12 @@ linux_make_mappings_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
 				    char *note_data, int *note_size)
 {
   struct cleanup *cleanup;
-  struct obstack data_obstack, filename_obstack;
   struct linux_make_mappings_data mapping_data;
   struct type *long_type
     = arch_integer_type (gdbarch, gdbarch_long_bit (gdbarch), 0, "long");
   gdb_byte buf[sizeof (ULONGEST)];
 
-  obstack_init (&data_obstack);
+  auto_obstack data_obstack, filename_obstack;
-  cleanup = make_cleanup_obstack_free (&data_obstack);
-  obstack_init (&filename_obstack);
-  make_cleanup_obstack_free (&filename_obstack);
 
   mapping_data.file_count = 0;
   mapping_data.data_obstack = &data_obstack;
@@ -1548,7 +1544,6 @@ linux_make_mappings_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
 				      obstack_object_size (&data_obstack));
     }
 
-  do_cleanups (cleanup);
   return note_data;
 }
 

gdb/printcmd.c

@@ -2255,8 +2255,6 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
 					 "wchar_t", NULL, 0);
   int wcwidth = TYPE_LENGTH (wctype);
   gdb_byte *buf = (gdb_byte *) alloca (wcwidth);
-  struct obstack output;
-  struct cleanup *inner_cleanup;
 
   tem = value_as_address (value);
 
@@ -2275,8 +2273,7 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
     read_memory (tem, str, j);
   memset (&str[j], 0, wcwidth);
 
-  obstack_init (&output);
+  auto_obstack output;
-  inner_cleanup = make_cleanup_obstack_free (&output);
 
   convert_between_encodings (target_wide_charset (gdbarch),
 			     host_charset (),
@@ -2285,7 +2282,6 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
   obstack_grow_str0 (&output, "");
 
   fprintf_filtered (stream, format, obstack_base (&output));
-  do_cleanups (inner_cleanup);
 }
 
 /* Subroutine of ui_printf to simplify it.
@@ -2531,8 +2527,6 @@ ui_printf (const char *arg, struct ui_file *stream)
 	      struct type *wctype = lookup_typename (current_language, gdbarch,
 						     "wchar_t", NULL, 0);
 	      struct type *valtype;
-	      struct obstack output;
-	      struct cleanup *inner_cleanup;
 	      const gdb_byte *bytes;
 
 	      valtype = value_type (val_args[i]);
@@ -2542,8 +2536,7 @@ ui_printf (const char *arg, struct ui_file *stream)
 
 	      bytes = value_contents (val_args[i]);
 
-	      obstack_init (&output);
+	      auto_obstack output;
-	      inner_cleanup = make_cleanup_obstack_free (&output);
 
 	      convert_between_encodings (target_wide_charset (gdbarch),
 					 host_charset (),
@@ -2554,7 +2547,6 @@ ui_printf (const char *arg, struct ui_file *stream)
 
 	      fprintf_filtered (stream, current_substring,
                                 obstack_base (&output));
-	      do_cleanups (inner_cleanup);
 	    }
 	    break;
 	  case double_arg:

gdb/rust-exp.y

@@ -185,7 +185,7 @@ static int unit_testing;
 
 /* Obstack for data temporarily allocated during parsing.  */
 
-static struct obstack work_obstack;
+static auto_obstack work_obstack;
 
 /* Result of parsing.  Points into work_obstack.  */
 
@@ -2446,13 +2446,17 @@ int
 rust_parse (struct parser_state *state)
 {
   int result;
-  struct cleanup *cleanup;
 
-  obstack_init (&work_obstack);
+  work_obstack.clear ();
-  cleanup = make_cleanup_obstack_free (&work_obstack);
+
   rust_ast = NULL;
 
   pstate = state;
+
+  /* Note that parsing (within rustyyparse) freely installs cleanups
+     assuming they're run here (below).  */
+  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+
   result = rustyyparse ();
 
   if (!result || (parse_completion && rust_ast != NULL))
@@ -2631,7 +2635,7 @@ rust_lex_tests (void)
 {
   int i;
 
-  obstack_init (&work_obstack);
+  work_obstack.clear ();
   unit_testing = 1;
 
   rust_lex_test_one ("", 0);
@@ -2722,7 +2726,6 @@ rust_lex_tests (void)
   rust_lex_test_completion ();
   rust_lex_test_push_back ();
 
-  obstack_free (&work_obstack, NULL);
   unit_testing = 0;
 }
 

gdb/utils.c

@@ -166,24 +166,6 @@ make_cleanup_fclose (FILE *file)
   return make_cleanup (do_fclose_cleanup, file);
 }
 
-/* Helper function which does the work for make_cleanup_obstack_free.  */
-
-static void
-do_obstack_free (void *arg)
-{
-  struct obstack *ob = (struct obstack *) arg;
-
-  obstack_free (ob, NULL);
-}
-
-/* Return a new cleanup that frees OBSTACK.  */
-
-struct cleanup *
-make_cleanup_obstack_free (struct obstack *obstack)
-{
-  return make_cleanup (do_obstack_free, obstack);
-}
-
 /* Helper function for make_cleanup_ui_out_redirect_pop.  */
 
 static void
@@ -1277,13 +1259,10 @@ query (const char *ctlstr, ...)
 static int
 host_char_to_target (struct gdbarch *gdbarch, int c, int *target_c)
 {
-  struct obstack host_data;
   char the_char = c;
-  struct cleanup *cleanups;
   int result = 0;
 
-  obstack_init (&host_data);
+  auto_obstack host_data;
-  cleanups = make_cleanup_obstack_free (&host_data);
 
   convert_between_encodings (target_charset (gdbarch), host_charset (),
 			     (gdb_byte *) &the_char, 1, 1,
@@ -1295,7 +1274,6 @@ host_char_to_target (struct gdbarch *gdbarch, int c, int *target_c)
       *target_c = *(char *) obstack_base (&host_data);
     }
 
-  do_cleanups (cleanups);
   return result;
 }
 

gdb/utils.h

@@ -78,9 +78,6 @@ extern struct cleanup *(make_cleanup_free_section_addr_info
 
 extern struct cleanup *make_cleanup_fclose (FILE *file);
 
-struct obstack;
-extern struct cleanup *make_cleanup_obstack_free (struct obstack *obstack);
-
 extern struct cleanup *make_cleanup_restore_integer (int *variable);
 extern struct cleanup *make_cleanup_restore_uinteger (unsigned int *variable);
 

gdb/valprint.c

@@ -2484,8 +2484,6 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
 {
   enum bfd_endian byte_order
     = gdbarch_byte_order (get_type_arch (type));
-  struct obstack wchar_buf, output;
-  struct cleanup *cleanups;
   gdb_byte *buf;
   int need_escape = 0;
 
@@ -2495,8 +2493,7 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
   wchar_iterator iter (buf, TYPE_LENGTH (type), encoding, TYPE_LENGTH (type));
 
   /* This holds the printable form of the wchar_t data.  */
-  obstack_init (&wchar_buf);
+  auto_obstack wchar_buf;
-  cleanups = make_cleanup_obstack_free (&wchar_buf);
 
   while (1)
     {
@@ -2543,8 +2540,7 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
     }
 
   /* The output in the host encoding.  */
-  obstack_init (&output);
+  auto_obstack output;
-  make_cleanup_obstack_free (&output);
 
   convert_between_encodings (INTERMEDIATE_ENCODING, host_charset (),
 			     (gdb_byte *) obstack_base (&wchar_buf),
@@ -2553,8 +2549,6 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
   obstack_1grow (&output, '\0');
 
   fputs_filtered ((const char *) obstack_base (&output), stream);
-
-  do_cleanups (cleanups);
 }
 
 /* Return the repeat count of the next character/byte in ITER,
@@ -2813,7 +2807,6 @@ generic_printstr (struct ui_file *stream, struct type *type,
   enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));
   unsigned int i;
   int width = TYPE_LENGTH (type);
-  struct obstack wchar_buf, output;
   struct cleanup *cleanup;
   int finished = 0;
   struct converted_character *last;
@@ -2885,8 +2878,7 @@ generic_printstr (struct ui_file *stream, struct type *type,
 
   /* WCHAR_BUF is the obstack we use to represent the string in
      wchar_t form.  */
-  obstack_init (&wchar_buf);
+  auto_obstack wchar_buf;
-  make_cleanup_obstack_free (&wchar_buf);
 
   /* Print the output string to the obstack.  */
   print_converted_chars_to_obstack (&wchar_buf, converted_chars, quote_char,
@@ -2896,8 +2888,7 @@ generic_printstr (struct ui_file *stream, struct type *type,
     obstack_grow_wstr (&wchar_buf, LCST ("..."));
 
   /* OUTPUT is where we collect `char's for printing.  */
-  obstack_init (&output);
+  auto_obstack output;
-  make_cleanup_obstack_free (&output);
 
   convert_between_encodings (INTERMEDIATE_ENCODING, host_charset (),
 			     (gdb_byte *) obstack_base (&wchar_buf),