gdb/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright 1990 Free Software Foundation
   3                   Written May 1989 by Mike Haertel.
   4
   5    The author may be reached (Email) at the address mike@ai.mit.edu,
   6    or (US mail) as Mike Haertel c/o Free Software Foundation.
   7
   8 This program is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2 of the License, or
  11 (at your option) any later version.
  12
  13 This program is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with this program; if not, write to the Free Software
  20 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  21
  22 #include "ansidecl.h"
  23 #include "gmalloc.h"
  24
  25 /* Old hook values.  */
  26 static void EXFUN((*old_free_hook), (PTR ptr));
  27 static PTR EXFUN((*old_malloc_hook), (size_t size));
  28 static PTR EXFUN((*old_realloc_hook), (PTR ptr, size_t size));
  29
  30
  31 /* Function to call when something awful happens. */
  32 extern void abort();
  33 static void EXFUN((*abortfunc), (void)) = (void (*)()) abort;
  34
  35 /* Arbitrary magical numbers.  */
  36 #define MAGICWORD       0xfedabeeb
  37 #define MAGICBYTE       ((char) 0xd7)
  38
  39 struct hdr
  40   {
  41     size_t size;                /* Exact size requested by user.  */
  42     unsigned int magic;         /* Magic number to check header integrity.  */
  43   };
  44
  45 static void
  46 DEFUN(checkhdr, (hdr), CONST struct hdr *hdr)
  47 {
  48   if (hdr->magic != MAGICWORD || ((char *) &hdr[1])[hdr->size] != MAGICBYTE)
  49     (*abortfunc)();
  50 }
  51
  52 static void
  53 DEFUN(freehook, (ptr), PTR ptr)
  54 {
  55   struct hdr *hdr = ((struct hdr *) ptr) - 1;
  56   checkhdr(hdr);
  57   hdr->magic = 0;
  58   __free_hook = old_free_hook;
  59   free(hdr);
  60   __free_hook = freehook;
  61 }
  62
  63 static PTR
  64 DEFUN(mallochook, (size), size_t size)
  65 {
  66   struct hdr *hdr;
  67
  68   __malloc_hook = old_malloc_hook;
  69   hdr = (struct hdr *) malloc(sizeof(struct hdr) + size + 1);
  70   __malloc_hook = mallochook;
  71   if (hdr == NULL)
  72     return NULL;
  73
  74   hdr->size = size;
  75   hdr->magic = MAGICWORD;
  76   ((char *) &hdr[1])[size] = MAGICBYTE;
  77   return (PTR) (hdr + 1);
  78 }
  79
  80 static PTR
  81 DEFUN(reallochook, (ptr, size), PTR ptr AND size_t size)
  82 {
  83   struct hdr *hdr = ((struct hdr *) ptr) - 1;
  84
  85   checkhdr(hdr);
  86   __free_hook = old_free_hook;
  87   __malloc_hook = old_malloc_hook;
  88   __realloc_hook = old_realloc_hook;
  89   hdr = (struct hdr *) realloc((PTR) hdr, sizeof(struct hdr) + size + 1);
  90   __free_hook = freehook;
  91   __malloc_hook = mallochook;
  92   __realloc_hook = reallochook;
  93   if (hdr == NULL)
  94     return NULL;
  95
  96   hdr->size = size;
  97   ((char *) &hdr[1])[size] = MAGICBYTE;
  98   return (PTR) (hdr + 1);
  99 }
 100
 101 void
 102 DEFUN(mcheck, (func), void EXFUN((*func), (void)))
 103 {
 104   static int mcheck_used = 0;
 105
 106   if (func)
 107     abortfunc = func;
 108
 109   /* These hooks may not be safely inserted if malloc is already in use.  */
 110   if (!__malloc_initialized && !mcheck_used)
 111     {
 112       old_free_hook = __free_hook;
 113       __free_hook = freehook;
 114       old_malloc_hook = __malloc_hook;
 115       __malloc_hook = mallochook;
 116       old_realloc_hook = __realloc_hook;
 117       __realloc_hook = reallochook;
 118       mcheck_used = 1;
 119     }
 120 }