[PATCH] (gmem.c) ENABLE_MEM_CHECK bug

[Martin Pool <mbp wistful humbug org au>]

Attached is a tiny patch to fix a bug that causes g_malloc0 to break
its invariants when ENABLE_MEM_CHECK is defined and ENABLE_MEM_PROFILE
is not.  The bug causes a coredump in testglib.c using the glib-1.1.2
source.

-- 
Martin Pool



*** gmem.c.~1~	Thu Jun 11 09:21:13 1998
--- gmem.c	Sat Aug 22 15:28:45 1998
***************
*** 1,6 ****
  /* GLIB - Library of useful routines for C programming
!  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Library General Public
   * License as published by the Free Software Foundation; either
--- 1,6 ----
  /* GLIB - Library of useful routines for C programming
!  * Copyright (C) 1995-1998  Peter Mattis, Spencer Kimball and Josh MacDonald
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Library General Public
   * License as published by the Free Software Foundation; either
***************
*** 22,29 ****
--- 22,45 ----
  
  /* #define ENABLE_MEM_PROFILE */
  /* #define ENABLE_MEM_CHECK */
  
+ /*
+  * This library can check for some attempts to do illegal things to
+  * memory (ENABLE_MEM_CHECK), and can do profiling
+  * (ENABLE_MEM_PROFILE).  Both features are implemented by storing
+  * words before the start of the memory chunk.
+  *
+  * The first, at offset -2*SIZEOF_LONG, is used only if
+  * ENABLE_MEM_CHECK is set, and stores 0 after the memory has been
+  * allocated and 1 when it has been freed.  The second, at offset
+  * -SIZEOF_LONG, is used if either flag is set and stores the size of
+  * the block.
+  *
+  * The MEM_CHECK flag is checked when memory is realloc'd and free'd,
+  * and it can be explicitly checked before using a block by calling
+  * g_mem_check().
+  */
  
  #define MAX_MEM_AREA  65536L
  #define MEM_AREA_SIZE 4L
  
***************
*** 167,175 ****
    if (size == 0)
      return NULL;
  
  
! #ifdef ENABLE_MEM_PROFILE
    size += SIZEOF_LONG;
  #endif /* ENABLE_MEM_PROFILE */
  
  #ifdef ENABLE_MEM_CHECK
--- 183,191 ----
    if (size == 0)
      return NULL;
  
  
! #if defined(ENABLE_MEM_PROFILE) || defined(ENABLE_MEM_CHECK)
    size += SIZEOF_LONG;
  #endif /* ENABLE_MEM_PROFILE */
  
  #ifdef ENABLE_MEM_CHECK
***************
*** 350,358 ****
  
    t = (gulong*) ((guchar*) mem - SIZEOF_LONG - SIZEOF_LONG);
  
    if (*t >= 1)
!     g_warning ("mem: 0x%08x has been freed: %lu\n", (gulong) mem, *t);
  #endif /* ENABLE_MEM_CHECK */
  }
  
  GMemChunk*
--- 366,374 ----
  
    t = (gulong*) ((guchar*) mem - SIZEOF_LONG - SIZEOF_LONG);
  
    if (*t >= 1)
!     g_warning ("mem: 0x%p has been freed: %lu\n", mem, *t);
  #endif /* ENABLE_MEM_CHECK */
  }
  
  GMemChunk*