gnu/lib/libmalloc/mtrace.c

   1 /* More debugging hooks for `malloc'.
   2    Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
   3                  Written April 2, 1991 by John Gilmore of Cygnus Support.
   4                  Based on mcheck.c by Mike Haertel.
   5
   6 This library is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public License as
   8 published by the Free Software Foundation; either version 2 of the
   9 License, or (at your option) any later version.
  10
  11 This library is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with this library; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  19 Cambridge, MA 02139, USA.
  20
  21    The author may be reached (Email) at the address mike@ai.mit.edu,
  22    or (US mail) as Mike Haertel c/o Free Software Foundation.  */
  23
  24 #ifndef _MALLOC_INTERNAL
  25 #define _MALLOC_INTERNAL
  26 #include <malloc.h>
  27 #endif
  28
  29 #include <stdio.h>
  30
  31 #ifndef __GNU_LIBRARY__
  32 extern char *getenv ();
  33 #else
  34 #include <stdlib.h>
  35 #endif
  36
  37 static FILE *mallstream;
  38 static char mallenv[]= "MALLOC_TRACE";
  39 static char mallbuf[BUFSIZ];    /* Buffer for the output.  */
  40
  41 /* Address to breakpoint on accesses to... */
  42 __ptr_t mallwatch;
  43
  44 /* Old hook values.  */
  45 static void (*tr_old_free_hook) __P ((__ptr_t ptr));
  46 static __ptr_t (*tr_old_malloc_hook) __P ((size_t size));
  47 static __ptr_t (*tr_old_realloc_hook) __P ((__ptr_t ptr, size_t size));
  48
  49 /* This function is called when the block being alloc'd, realloc'd, or
  50    freed has an address matching the variable "mallwatch".  In a debugger,
  51    set "mallwatch" to the address of interest, then put a breakpoint on
  52    tr_break.  */
  53
  54 void tr_break __P ((void));
  55 void
  56 tr_break ()
  57 {
  58 }
  59
  60 static void tr_freehook __P ((__ptr_t));
  61 static void
  62 tr_freehook (ptr)
  63      __ptr_t ptr;
  64 {
  65   fprintf (mallstream, "- %p\n", ptr);  /* Be sure to print it first.  */
  66   if (ptr == mallwatch)
  67     tr_break ();
  68   __free_hook = tr_old_free_hook;
  69   free (ptr);
  70   __free_hook = tr_freehook;
  71 }
  72
  73 static __ptr_t tr_mallochook __P ((size_t));
  74 static __ptr_t
  75 tr_mallochook (size)
  76      size_t size;
  77 {
  78   __ptr_t hdr;
  79
  80   __malloc_hook = tr_old_malloc_hook;
  81   hdr = (__ptr_t) malloc (size);
  82   __malloc_hook = tr_mallochook;
  83
  84   /* We could be printing a NULL here; that's OK.  */
  85   fprintf (mallstream, "+ %p %x\n", hdr, size);
  86
  87   if (hdr == mallwatch)
  88     tr_break ();
  89
  90   return hdr;
  91 }
  92
  93 static __ptr_t tr_reallochook __P ((__ptr_t, size_t));
  94 static __ptr_t
  95 tr_reallochook (ptr, size)
  96      __ptr_t ptr;
  97      size_t size;
  98 {
  99   __ptr_t hdr;
 100
 101   if (ptr == mallwatch)
 102     tr_break ();
 103
 104   __free_hook = tr_old_free_hook;
 105   __malloc_hook = tr_old_malloc_hook;
 106   __realloc_hook = tr_old_realloc_hook;
 107   hdr = (__ptr_t) realloc (ptr, size);
 108   __free_hook = tr_freehook;
 109   __malloc_hook = tr_mallochook;
 110   __realloc_hook = tr_reallochook;
 111   if (hdr == NULL)
 112     /* Failed realloc.  */
 113     fprintf (mallstream, "! %p %x\n", ptr, size);
 114   else
 115     fprintf (mallstream, "< %p\n> %p %x\n", ptr, hdr, size);
 116
 117   if (hdr == mallwatch)
 118     tr_break ();
 119
 120   return hdr;
 121 }
 122
 123 /* We enable tracing if either the environment variable MALLOC_TRACE
 124    is set, or if the variable mallwatch has been patched to an address
 125    that the debugging user wants us to stop on.  When patching mallwatch,
 126    don't forget to set a breakpoint on tr_break!  */
 127
 128 void
 129 mtrace ()
 130 {
 131   char *mallfile;
 132
 133   mallfile = getenv (mallenv);
 134   if (mallfile != NULL || mallwatch != NULL)
 135     {
 136       mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "w");
 137       if (mallstream != NULL)
 138         {
 139           /* Be sure it doesn't malloc its buffer!  */
 140           setbuf (mallstream, mallbuf);
 141           fprintf (mallstream, "= Start\n");
 142           tr_old_free_hook = __free_hook;
 143           __free_hook = tr_freehook;
 144           tr_old_malloc_hook = __malloc_hook;
 145           __malloc_hook = tr_mallochook;
 146           tr_old_realloc_hook = __realloc_hook;
 147           __realloc_hook = tr_reallochook;
 148         }
 149     }
 150 }