Make ada_decode not use a static buffer

This makes it safer to use in general, and also allows using it on a
background thread in the future.

Inspired by tromey's patch at:
https://github.com/tromey/gdb/commit/1226cbdfa436297a5dec054d94592c45891afa93
(however, implemented in a different way)

gdb/ChangeLog:

2019-09-23  Christian Biesinger  <cbiesinger@google.com>

	* ada-exp.y (write_object_remaining): Update.
	* ada-lang.c (ada_decode): Return a std::string instead of a char*
	and eliminate the static buffer.
	(ada_decode_symbol): Update.
	(ada_la_decode): Update.
	(ada_sniff_from_mangled_name): Update.
	(is_valid_name_for_wild_match): Update.
	(ada_lookup_name_info::matches): Update and simplify.
	(name_matches_regex): Update.
	(ada_add_global_exceptions): Update.
	* ada-lang.h (ada_decode): Update signature.
	* ada-varobj.c (ada_varobj_describe_simple_array_child): Update.
	* dwarf-index-write.c (debug_names::insert): Update.

6 files changed, 52 insertions, 46 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4374348c8df..33951b88c63 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,19 @@
+2019-09-23  Christian Biesinger  <cbiesinger@google.com>
+
+	* ada-exp.y (write_object_remaining): Update.
+	* ada-lang.c (ada_decode): Return a std::string instead of a char*
+	and eliminate the static buffer.
+	(ada_decode_symbol): Update.
+	(ada_la_decode): Update.
+	(ada_sniff_from_mangled_name): Update.
+	(is_valid_name_for_wild_match): Update.
+	(ada_lookup_name_info::matches): Update and simplify.
+	(name_matches_regex): Update.
+	(ada_add_global_exceptions): Update.
+	* ada-lang.h (ada_decode): Update signature.
+	* ada-varobj.c (ada_varobj_describe_simple_array_child): Update.
+	* dwarf-index-write.c (debug_names::insert): Update.
+
 2019-09-21  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* solib-svr4.c (svr4_iterate_over_objfiles_in_search_order): Fix
diff --git a/gdb/ada-exp.y b/gdb/ada-exp.y
index c8a7b9c9c75..160e64bc05b 100644
--- a/gdb/ada-exp.y
+++ b/gdb/ada-exp.y
@@ -816,7 +816,7 @@ write_object_renaming (struct parser_state *par_state,
 			  renamed_entity_len);
   ada_lookup_encoded_symbol (name, orig_left_context, VAR_DOMAIN, &sym_info);
   if (sym_info.symbol == NULL)
-    error (_("Could not find renamed variable: %s"), ada_decode (name));
+    error (_("Could not find renamed variable: %s"), ada_decode (name).c_str ());
   else if (SYMBOL_CLASS (sym_info.symbol) == LOC_TYPEDEF)
     /* We have a renaming of an old-style renaming symbol.  Don't
        trust the block information.  */
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index c34733e754f..063b98bde5b 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -1105,22 +1105,16 @@ ada_remove_po_subprogram_suffix (const char *encoded, int *len)
 
 /* If ENCODED follows the GNAT entity encoding conventions, then return
    the decoded form of ENCODED.  Otherwise, return "<%s>" where "%s" is
-   replaced by ENCODED.
+   replaced by ENCODED.  */
 
-   The resulting string is valid until the next call of ada_decode.
-   If the string is unchanged by decoding, the original string pointer
-   is returned.  */
-
-const char *
+std::string
 ada_decode (const char *encoded)
 {
   int i, j;
   int len0;
   const char *p;
-  char *decoded;
   int at_start_name;
-  static char *decoding_buffer = NULL;
-  static size_t decoding_buffer_size = 0;
+  std::string decoded;
 
   /* With function descriptors on PPC64, the value of a symbol named
      ".FN", if it exists, is the entry point of the function "FN".  */
@@ -1179,8 +1173,7 @@ ada_decode (const char *encoded)
 
   /* Make decoded big enough for possible expansion by operator name.  */
 
-  GROW_VECT (decoding_buffer, decoding_buffer_size, 2 * len0 + 1);
-  decoded = decoding_buffer;
+  decoded.resize (2 * len0 + 1, 'X');
 
   /* Remove trailing __{digit}+ or trailing ${digit}+.  */
 
@@ -1217,7 +1210,7 @@ ada_decode (const char *encoded)
                             op_len - 1) == 0)
                   && !isalnum (encoded[i + op_len]))
                 {
-                  strcpy (decoded + j, ada_opname_table[k].decoded);
+                  strcpy (&decoded.front() + j, ada_opname_table[k].decoded);
                   at_start_name = 0;
                   i += op_len;
                   j += strlen (ada_opname_table[k].decoded);
@@ -1338,27 +1331,22 @@ ada_decode (const char *encoded)
           j += 1;
         }
     }
-  decoded[j] = '\000';
+  decoded.resize (j);
 
   /* Decoded names should never contain any uppercase character.
      Double-check this, and abort the decoding if we find one.  */
 
-  for (i = 0; decoded[i] != '\0'; i += 1)
+  for (i = 0; i < decoded.length(); ++i)
     if (isupper (decoded[i]) || decoded[i] == ' ')
       goto Suppress;
 
-  if (strcmp (decoded, encoded) == 0)
-    return encoded;
-  else
-    return decoded;
+  return decoded;
 
 Suppress:
-  GROW_VECT (decoding_buffer, decoding_buffer_size, strlen (encoded) + 3);
-  decoded = decoding_buffer;
   if (encoded[0] == '<')
-    strcpy (decoded, encoded);
+    decoded = encoded;
   else
-    xsnprintf (decoded, decoding_buffer_size, "<%s>", encoded);
+    decoded = '<' + std::string(encoded) + '>';
   return decoded;
 
 }
@@ -1389,13 +1377,13 @@ ada_decode_symbol (const struct general_symbol_info *arg)
 
   if (!gsymbol->ada_mangled)
     {
-      const char *decoded = ada_decode (gsymbol->name);
+      std::string decoded = ada_decode (gsymbol->name);
       struct obstack *obstack = gsymbol->language_specific.obstack;
 
       gsymbol->ada_mangled = 1;
 
       if (obstack != NULL)
-	*resultp = obstack_strdup (obstack, decoded);
+	*resultp = obstack_strdup (obstack, decoded.c_str ());
       else
         {
 	  /* Sometimes, we can't find a corresponding objfile, in
@@ -1404,10 +1392,10 @@ ada_decode_symbol (const struct general_symbol_info *arg)
 	     significant memory leak (FIXME).  */
 
           char **slot = (char **) htab_find_slot (decoded_names_store,
-                                                  decoded, INSERT);
+                                                  decoded.c_str (), INSERT);
 
           if (*slot == NULL)
-            *slot = xstrdup (decoded);
+            *slot = xstrdup (decoded.c_str ());
           *resultp = *slot;
         }
     }
@@ -1418,7 +1406,7 @@ ada_decode_symbol (const struct general_symbol_info *arg)
 static char *
 ada_la_decode (const char *encoded, int options)
 {
-  return xstrdup (ada_decode (encoded));
+  return xstrdup (ada_decode (encoded).c_str ());
 }
 
 /* Implement la_sniff_from_mangled_name for Ada.  */
@@ -1426,11 +1414,11 @@ ada_la_decode (const char *encoded, int options)
 static int
 ada_sniff_from_mangled_name (const char *mangled, char **out)
 {
-  const char *demangled = ada_decode (mangled);
+  std::string demangled = ada_decode (mangled);
 
   *out = NULL;
 
-  if (demangled != mangled && demangled != NULL && demangled[0] != '<')
+  if (demangled != mangled && demangled[0] != '<')
     {
       /* Set the gsymbol language to Ada, but still return 0.
 	 Two reasons for that:
@@ -5993,7 +5981,7 @@ is_name_suffix (const char *str)
 static int
 is_valid_name_for_wild_match (const char *name0)
 {
-  const char *decoded_name = ada_decode (name0);
+  std::string decoded_name = ada_decode (name0);
   int i;
 
   /* If the decoded name starts with an angle bracket, it means that
@@ -6233,19 +6221,16 @@ ada_lookup_name_info::matches
   if (strncmp (sym_name, text, text_len) == 0)
     match = true;
 
+  std::string decoded_name = ada_decode (sym_name);
   if (match && !m_encoded_p)
     {
       /* One needed check before declaring a positive match is to verify
          that iff we are doing a verbatim match, the decoded version
          of the symbol name starts with '<'.  Otherwise, this symbol name
          is not a suitable completion.  */
-      const char *sym_name_copy = sym_name;
-      bool has_angle_bracket;
 
-      sym_name = ada_decode (sym_name);
-      has_angle_bracket = (sym_name[0] == '<');
+      bool has_angle_bracket = (decoded_name[0] == '<');
       match = (has_angle_bracket == m_verbatim_p);
-      sym_name = sym_name_copy;
     }
 
   if (match && !m_verbatim_p)
@@ -6269,7 +6254,7 @@ ada_lookup_name_info::matches
       /* Since we are doing wild matching, this means that TEXT
          may represent an unqualified symbol name.  We therefore must
          also compare TEXT against the unqualified name of the symbol.  */
-      sym_name = ada_unqualified_name (ada_decode (sym_name));
+      sym_name = ada_unqualified_name (decoded_name.c_str ());
 
       if (strncmp (sym_name, text, text_len) == 0)
 	match = true;
@@ -13494,7 +13479,7 @@ static bool
 name_matches_regex (const char *name, compiled_regex *preg)
 {
   return (preg == NULL
-	  || preg->exec (ada_decode (name), 0, NULL, 0) == 0);
+	  || preg->exec (ada_decode (name).c_str (), 0, NULL, 0) == 0);
 }
 
 /* Add all exceptions defined globally whose name name match
@@ -13527,8 +13512,8 @@ ada_add_global_exceptions (compiled_regex *preg,
 			   lookup_name_info::match_any (),
 			   [&] (const char *search_name)
 			   {
-			     const char *decoded = ada_decode (search_name);
-			     return name_matches_regex (decoded, preg);
+			     std::string decoded = ada_decode (search_name);
+			     return name_matches_regex (decoded.c_str (), preg);
 			   },
 			   NULL,
 			   VARIABLES_DOMAIN);
diff --git a/gdb/ada-lang.h b/gdb/ada-lang.h
index 2fc3f523ca7..c7279d5ac39 100644
--- a/gdb/ada-lang.h
+++ b/gdb/ada-lang.h
@@ -227,7 +227,7 @@ extern struct type *ada_get_decoded_type (struct type *type);
 
 extern const char *ada_decode_symbol (const struct general_symbol_info *);
 
-extern const char *ada_decode (const char*);
+extern std::string ada_decode (const char*);
 
 extern enum language ada_update_initial_language (enum language);
 
diff --git a/gdb/ada-varobj.c b/gdb/ada-varobj.c
index a4d553d3786..1a5d0ac2393 100644
--- a/gdb/ada-varobj.c
+++ b/gdb/ada-varobj.c
@@ -624,6 +624,7 @@ ada_varobj_describe_simple_array_child (struct value *parent_value,
 	 of the array index type when such type qualification is
 	 needed.  */
       const char *index_type_name = NULL;
+      std::string decoded;
 
       /* If the index type is a range type, find the base type.  */
       while (TYPE_CODE (index_type) == TYPE_CODE_RANGE)
@@ -634,7 +635,10 @@ ada_varobj_describe_simple_array_child (struct value *parent_value,
 	{
 	  index_type_name = ada_type_name (index_type);
 	  if (index_type_name)
-	    index_type_name = ada_decode (index_type_name);
+	    {
+	      decoded = ada_decode (index_type_name);
+	      index_type_name = decoded.c_str ();
+	    }
 	}
 
       if (index_type_name != NULL)
diff --git a/gdb/dwarf-index-write.c b/gdb/dwarf-index-write.c
index 153c6792f0c..0947ba9ec14 100644
--- a/gdb/dwarf-index-write.c
+++ b/gdb/dwarf-index-write.c
@@ -714,13 +714,14 @@ public:
 	   name (of the form "<MumBle>") must be entered without the
 	   angle brackets.  Note that the current index is unusual,
 	   see PR symtab/24820 for details.  */
-	const char *decoded = ada_decode (name);
+	std::string decoded = ada_decode (name);
 	if (decoded[0] == '<')
 	  name = (char *) obstack_copy0 (&m_string_obstack,
-					 decoded + 1,
-					 strlen (decoded + 1) - 1);
+					 decoded.c_str () + 1,
+					 decoded.length () - 2);
 	else
-	  name = obstack_strdup (&m_string_obstack, ada_encode (decoded));
+	  name = obstack_strdup (&m_string_obstack,
+				 ada_encode (decoded.c_str ()));
       }
 
     const auto insertpair