mtrace.c revision efc6f628e15de95bcd13e4f0ee223cb42115d520 
1/* More debugging hooks for `malloc'.
2   Copyright (C) 1991, 1992 Free Software Foundation, Inc.
3		 Written April 2, 1991 by John Gilmore of Cygnus Support.
4		 Based on mcheck.c by Mike Haertel.
5
6This library is free software; you can redistribute it and/or
7modify it under the terms of the GNU Library General Public License as
8published by the Free Software Foundation; either version 2 of the
9License, or (at your option) any later version.
10
11This library is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14Library General Public License for more details.
15
16You should have received a copy of the GNU Library General Public
17License along with this library; see the file COPYING.LIB.  If
18not, write to the Free Software Foundation, Inc., 675 Mass Ave,
19Cambridge, 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 "./mtrace.h"
27#endif
28
29#include <stdio.h>
30
31#ifndef	__GNU_LIBRARY__
32extern char *getenv ();
33#else
34#include <stdlib.h>
35#endif
36
37static FILE *mallstream;
38static char mallenv[]= "MALLOC_TRACE";
39static char mallbuf[BUFSIZ];	/* Buffer for the output.  */
40
41/* Address to breakpoint on accesses to... */
42__ptr_t mallwatch;
43
44/* Old hook values.  */
45static void (*tr_old_free_hook) __P ((__ptr_t ptr));
46static __ptr_t (*tr_old_malloc_hook) __P ((size_t size));
47static __ptr_t (*tr_old_realloc_hook) __P ((__ptr_t ptr, size_t size));
48
49/*
50 * Added by TYT, 10/10/93 --- so that we can print
51 */
52FILE *malloc_get_mallstream()
53{
54	return mallstream;
55}
56
57/* This function is called when the block being alloc'd, realloc'd, or
58   freed has an address matching the variable "mallwatch".  In a debugger,
59   set "mallwatch" to the address of interest, then put a breakpoint on
60   tr_break.  */
61
62void tr_break __P ((void));
63void
64tr_break ()
65{
66}
67
68static void tr_freehook __P ((__ptr_t));
69static void
70tr_freehook (ptr)
71     __ptr_t ptr;
72{
73  fprintf (mallstream, "- %p\n", ptr);	/* Be sure to print it first.  */
74  if (ptr == mallwatch)
75    tr_break ();
76  __free_hook = tr_old_free_hook;
77  free (ptr);
78  __free_hook = tr_freehook;
79}
80
81static __ptr_t tr_mallochook __P ((size_t));
82static __ptr_t
83tr_mallochook (size)
84     size_t size;
85{
86  __ptr_t hdr;
87
88  __malloc_hook = tr_old_malloc_hook;
89  hdr = (__ptr_t) malloc (size);
90  __malloc_hook = tr_mallochook;
91
92  /* We could be printing a NULL here; that's OK.  */
93  fprintf (mallstream, "+ %p %d\n", hdr, size);
94
95  if (hdr == mallwatch)
96    tr_break ();
97
98  return hdr;
99}
100
101static __ptr_t tr_reallochook __P ((__ptr_t, size_t));
102static __ptr_t
103tr_reallochook (ptr, size)
104     __ptr_t ptr;
105     size_t size;
106{
107  __ptr_t hdr;
108
109  if (ptr == mallwatch)
110    tr_break ();
111
112  __free_hook = tr_old_free_hook;
113  __malloc_hook = tr_old_malloc_hook;
114  __realloc_hook = tr_old_realloc_hook;
115  hdr = (__ptr_t) realloc (ptr, size);
116  __free_hook = tr_freehook;
117  __malloc_hook = tr_mallochook;
118  __realloc_hook = tr_reallochook;
119  if (hdr == NULL)
120    /* Failed realloc.  */
121    fprintf (mallstream, "! %p %d\n", ptr, size);
122  else
123    fprintf (mallstream, "< %p\n> %p %d\n", ptr, hdr, size);
124
125  if (hdr == mallwatch)
126    tr_break ();
127
128  return hdr;
129}
130
131/* We enable tracing if either the environment variable MALLOC_TRACE
132   is set, or if the variable mallwatch has been patched to an address
133   that the debugging user wants us to stop on.  When patching mallwatch,
134   don't forget to set a breakpoint on tr_break!  */
135
136void
137mtrace ()
138{
139  char *mallfile;
140
141  mallfile = getenv (mallenv);
142  if (mallfile != NULL || mallwatch != NULL)
143    {
144      mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "w");
145      if (mallstream != NULL)
146	{
147	  /* Be sure it doesn't malloc its buffer!  */
148	  setbuf (mallstream, mallbuf);
149	  fprintf (mallstream, "= Start\n");
150	  tr_old_free_hook = __free_hook;
151	  __free_hook = tr_freehook;
152	  tr_old_malloc_hook = __malloc_hook;
153	  __malloc_hook = tr_mallochook;
154	  tr_old_realloc_hook = __realloc_hook;
155	  __realloc_hook = tr_reallochook;
156	}
157    }
158}
159