[RFA] Avoid memory leaks in set_language function.

["Pierre Muller" <pierre.muller@ics-cnrs.unistra.fr>]

With the troubles that I have with my patch,
I started looking into a memory debugger...
  I finally started to use drmemory
for mingw compiled GDB executables.

This also revealed a few memory leaks
related to repeated add_language function calls.


Error #76: LEAK 34 direct bytes 0x0370aa58-0x0370aa7a + 0 indirect bytes
# 0 xmalloc
[../../puresrc/gdb/common/common-utils.c:50]
# 1 xstrdup
[../../puresrc/libiberty/xstrdup.c:34]
# 2 add_setshow_cmd_full
[../../puresrc/gdb/cli/cli-decode.c:450]
# 3 add_setshow_enum_cmd
[../../puresrc/gdb/cli/cli-decode.c:489]
# 4 add_language                          [../../puresrc/gdb/language.c:588]
# 5 _initialize_m2_language               [../../puresrc/gdb/m2-lang.c:446]
# 6 initialize_all_files
[e:\cygwin-1.7\usr\local\src\gdbcvs\mingw32-puresrc-dwarf\gdb/init.c:212]
# 7 gdb_init                              [../../puresrc/gdb/top.c:1707]
# 8 captured_main                         [../../puresrc/gdb/main.c:731]
# 9 catch_errors
[../../puresrc/gdb/exceptions.c:546]
#10 gdb_main                              [../../puresrc/gdb/main.c:1041]
#11 main                                  [../../puresrc/gdb/gdb.c:34]


 The patch below fixes that memory leaks by 
xfree'ing doc fields if flags contains a new flag called DOC_ALLOCATED.
This flag is set in add_setshom_cmd_full
and sometimes also in add_alias_cmd.



Pierre Muller
GDB pascal language maintainer


2012-12-05  Pierre Muller  <muller@sourceware.org>

        Avoid memory leaks on struct cmd_list_element.doc field.
        * cli/cli-decode.c (add_alias_cmd): Make a copy of doc field
        if flags contains DOC_ALLOCATED.
        (add_setshow_cmd_full): Add DOC_ALLOCATED to set and show
        flags.
        (delete_cmd): Handle DOC_ALLOCATED flag.
        * cli/cli-decode.h (DOC_ALLOCATED): New macro for use
        in flags filed of struct cmd_list_element.
        (struct cmd_list_element): Document new flag item.

Index: src/gdb/cli/cli-decode.c
===================================================================
RCS file: /cvs/src/src/gdb/cli/cli-decode.c,v
retrieving revision 1.110
diff -u -p -r1.110 cli-decode.c
--- src/gdb/cli/cli-decode.c    20 Nov 2012 21:02:35 -0000      1.110
+++ src/gdb/cli/cli-decode.c    5 Dec 2012 17:02:25 -0000
@@ -306,6 +306,13 @@ add_alias_cmd (char *name, char *oldname
     }

   c = add_cmd (name, class, NULL, old->doc, list);
+
+  /* If OLD->DOC can be freed, we should make another copy.  */
+  if (old->flags & DOC_ALLOCATED)
+    {
+      c->doc = xstrdup (old->doc);
+      c->flags |= DOC_ALLOCATED;
+    }
   /* NOTE: Both FUNC and all the FUNCTIONs need to be copied.  */
   c->func = old->func;
   c->function = old->function;
@@ -451,6 +458,8 @@ add_setshow_cmd_full (char *name,
     }
   set = add_set_or_show_cmd (name, set_cmd, class, var_type, var,
                             full_set_doc, set_list);
+  set->flags |= DOC_ALLOCATED;
+
   if (set_func != NULL)
     set_cmd_sfunc (set, set_func);

@@ -458,6 +467,7 @@ add_setshow_cmd_full (char *name,

   show = add_set_or_show_cmd (name, show_cmd, class, var_type, var,
                              full_show_doc, show_list);
+  show->flags |= DOC_ALLOCATED;
   show->show_value_func = show_func;

   if (set_result != NULL)
@@ -769,6 +779,8 @@ delete_cmd (char *name, struct cmd_list_
          *prehookee = iter->hookee_pre;
          if (iter->hookee_post)
            iter->hookee_post->hook_post = 0;
+         if (iter->doc && iter->flags & DOC_ALLOCATED)
+           xfree (iter->doc);
          *posthook = iter->hook_post;
          *posthookee = iter->hookee_post;

Index: src/gdb/cli/cli-decode.h
===================================================================
RCS file: /cvs/src/src/gdb/cli/cli-decode.h,v
retrieving revision 1.43
diff -u -p -r1.43 cli-decode.h
--- src/gdb/cli/cli-decode.h    9 Aug 2012 12:53:43 -0000       1.43
+++ src/gdb/cli/cli-decode.h    5 Dec 2012 17:02:25 -0000
@@ -51,7 +51,7 @@ cmd_types;
 #define CMD_DEPRECATED            0x1
 #define DEPRECATED_WARN_USER      0x2
 #define MALLOCED_REPLACEMENT      0x4
-
+#define DOC_ALLOCATED             0x8
 struct cmd_list_element
   {
     /* Points to next command in this list.  */
@@ -112,7 +112,9 @@ struct cmd_list_element
        memory for replacement is malloc'ed.  When a command is
        undeprecated or re-deprecated at runtime we don't want to risk
        calling free on statically allocated memory, so we check this
-       flag.  */
+       flag.
+
+       bit 3: DOC_ALLOCATED, set if the doc field should be xfree'd.  */

     int flags;