Bug Summary

File:compat/obstack.c
Location:line 258, column 19
Description:Access to field 'prev' results in a dereference of a null pointer (loaded from variable 'new_chunk')

Annotated Source Code

1/* obstack.c - subroutines used implicitly by object stack macros
2 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C 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 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
19 Boston, MA 02110-1301, USA. */
20
21#include "git-compat-util.h"
22#include <gettext.h>
23#include "obstack.h"
24
25/* NOTE BEFORE MODIFYING THIS FILE: This version number must be
26 incremented whenever callers compiled using an old obstack.h can no
27 longer properly call the functions in this obstack.c. */
28#define OBSTACK_INTERFACE_VERSION1 1
29
30/* Comment out all this code if we are using the GNU C Library, and are not
31 actually compiling the library itself, and the installed library
32 supports the same library interface we do. This code is part of the GNU
33 C Library, but also included in many other GNU distributions. Compiling
34 and linking in this code is a waste when using the GNU C library
35 (especially if it is a shared library). Rather than having every GNU
36 program understand `configure --with-gnu-libc' and omit the object
37 files, it is simpler to just do this in the source for each such file. */
38
39#include <stdio.h> /* Random thing to get __GNU_LIBRARY__. */
40#if !defined _LIBC && defined __GNU_LIBRARY__ && __GNU_LIBRARY__ > 1
41# include <gnu-versions.h>
42# if _GNU_OBSTACK_INTERFACE_VERSION == OBSTACK_INTERFACE_VERSION1
43# define ELIDE_CODE
44# endif
45#endif
46
47#include <stddef.h>
48
49#ifndef ELIDE_CODE
50
51
52# if HAVE_INTTYPES_H
53# include <inttypes.h>
54# endif
55# if HAVE_STDINT_H || defined _LIBC
56# include <stdint.h>
57# endif
58
59/* Determine default alignment. */
60union fooround
61{
62 uintmax_t i;
63 long double d;
64 void *p;
65};
66struct fooalign
67{
68 char c;
69 union fooround u;
70};
71/* If malloc were really smart, it would round addresses to DEFAULT_ALIGNMENT.
72 But in fact it might be less smart and round addresses to as much as
73 DEFAULT_ROUNDING. So we prepare for it to do that. */
74enum
75 {
76 DEFAULT_ALIGNMENT = offsetof (struct fooalign, u)__builtin_offsetof(struct fooalign, u),
77 DEFAULT_ROUNDING = sizeof (union fooround)
78 };
79
80/* When we copy a long block of data, this is the unit to do it with.
81 On some machines, copying successive ints does not work;
82 in such a case, redefine COPYING_UNIT to `long' (if that works)
83 or `char' as a last resort. */
84# ifndef COPYING_UNITint
85# define COPYING_UNITint int
86# endif
87
88
89/* The functions allocating more room by calling `obstack_chunk_alloc'
90 jump to the handler pointed to by `obstack_alloc_failed_handler'.
91 This can be set to a user defined function which should either
92 abort gracefully or use longjump - but shouldn't return. This
93 variable by default points to the internal function
94 `print_and_abort'. */
95static void print_and_abort (void);
96void (*obstack_alloc_failed_handler) (void) = print_and_abort;
97
98# ifdef _LIBC
99# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_3_4)
100/* A looong time ago (before 1994, anyway; we're not sure) this global variable
101 was used by non-GNU-C macros to avoid multiple evaluation. The GNU C
102 library still exports it because somebody might use it. */
103struct obstack *_obstack_compat;
104compat_symbol (libc, _obstack_compat, _obstack, GLIBC_2_0);
105# endif
106# endif
107
108/* Define a macro that either calls functions with the traditional malloc/free
109 calling interface, or calls functions with the mmalloc/mfree interface
110 (that adds an extra first argument), based on the state of use_extra_arg.
111 For free, do not use ?:, since some compilers, like the MIPS compilers,
112 do not allow (expr) ? void : void. */
113
114# define CALL_CHUNKFUN(h, size)(((h) -> use_extra_arg) ? (*(h)->chunkfun) ((h)->extra_arg
, (size)) : (*(struct _obstack_chunk *(*) (long)) (h)->chunkfun
) ((size))) \
115 (((h) -> use_extra_arg) \
116 ? (*(h)->chunkfun) ((h)->extra_arg, (size)) \
117 : (*(struct _obstack_chunk *(*) (long)) (h)->chunkfun) ((size)))
118
119# define CALL_FREEFUN(h, old_chunk)do { if ((h) -> use_extra_arg) (*(h)->freefun) ((h)->
extra_arg, (old_chunk)); else (*(void (*) (void *)) (h)->freefun
) ((old_chunk)); } while (0) \
120 do { \
121 if ((h) -> use_extra_arg) \
122 (*(h)->freefun) ((h)->extra_arg, (old_chunk)); \
123 else \
124 (*(void (*) (void *)) (h)->freefun) ((old_chunk)); \
125 } while (0)
126
127
128/* Initialize an obstack H for use. Specify chunk size SIZE (0 means default).
129 Objects start on multiples of ALIGNMENT (0 means use default).
130 CHUNKFUN is the function to use to allocate chunks,
131 and FREEFUN the function to free them.
132
133 Return nonzero if successful, calls obstack_alloc_failed_handler if
134 allocation fails. */
135
136int
137_obstack_begin (struct obstack *h,
138 int size, int alignment,
139 void *(*chunkfun) (long),
140 void (*freefun) (void *))
141{
142 register struct _obstack_chunk *chunk; /* points to new chunk */
143
144 if (alignment == 0)
145 alignment = DEFAULT_ALIGNMENT;
146 if (size == 0)
147 /* Default size is what GNU malloc can fit in a 4096-byte block. */
148 {
149 /* 12 is sizeof (mhead) and 4 is EXTRA from GNU malloc.
150 Use the values for range checking, because if range checking is off,
151 the extra bytes won't be missed terribly, but if range checking is on
152 and we used a larger request, a whole extra 4096 bytes would be
153 allocated.
154
155 These number are irrelevant to the new GNU malloc. I suspect it is
156 less sensitive to the size of the request. */
157 int extra = ((((12 + DEFAULT_ROUNDING - 1) & ~(DEFAULT_ROUNDING - 1))
158 + 4 + DEFAULT_ROUNDING - 1)
159 & ~(DEFAULT_ROUNDING - 1));
160 size = 4096 - extra;
161 }
162
163 h->chunkfun = (struct _obstack_chunk * (*)(void *, long)) chunkfun;
164 h->freefun = (void (*) (void *, struct _obstack_chunk *)) freefun;
165 h->chunk_size = size;
166 h->alignment_mask = alignment - 1;
167 h->use_extra_arg = 0;
168
169 chunk = h->chunk = CALL_CHUNKFUN (h, h -> chunk_size)(((h) -> use_extra_arg) ? (*(h)->chunkfun) ((h)->extra_arg
, (h -> chunk_size)) : (*(struct _obstack_chunk *(*) (long
)) (h)->chunkfun) ((h -> chunk_size)));
170 if (!chunk)
171 (*obstack_alloc_failed_handler) ();
172 h->next_free = h->object_base = __PTR_ALIGN ((char *) chunk, chunk->contents,((sizeof (long int) < sizeof (void *) ? ((char *) chunk) :
(char *) 0) + (((chunk->contents) - (sizeof (long int) <
sizeof (void *) ? ((char *) chunk) : (char *) 0) + (alignment
- 1)) & ~(alignment - 1)))
173 alignment - 1)((sizeof (long int) < sizeof (void *) ? ((char *) chunk) :
(char *) 0) + (((chunk->contents) - (sizeof (long int) <
sizeof (void *) ? ((char *) chunk) : (char *) 0) + (alignment
- 1)) & ~(alignment - 1)));
174 h->chunk_limit = chunk->limit
175 = (char *) chunk + h->chunk_size;
176 chunk->prev = NULL((void*)0);
177 /* The initial chunk now contains no empty object. */
178 h->maybe_empty_object = 0;
179 h->alloc_failed = 0;
180 return 1;
181}
182
183int
184_obstack_begin_1 (struct obstack *h, int size, int alignment,
185 void *(*chunkfun) (void *, long),
186 void (*freefun) (void *, void *),
187 void *arg)
188{
189 register struct _obstack_chunk *chunk; /* points to new chunk */
190
191 if (alignment == 0)
192 alignment = DEFAULT_ALIGNMENT;
193 if (size == 0)
194 /* Default size is what GNU malloc can fit in a 4096-byte block. */
195 {
196 /* 12 is sizeof (mhead) and 4 is EXTRA from GNU malloc.
197 Use the values for range checking, because if range checking is off,
198 the extra bytes won't be missed terribly, but if range checking is on
199 and we used a larger request, a whole extra 4096 bytes would be
200 allocated.
201
202 These number are irrelevant to the new GNU malloc. I suspect it is
203 less sensitive to the size of the request. */
204 int extra = ((((12 + DEFAULT_ROUNDING - 1) & ~(DEFAULT_ROUNDING - 1))
205 + 4 + DEFAULT_ROUNDING - 1)
206 & ~(DEFAULT_ROUNDING - 1));
207 size = 4096 - extra;
208 }
209
210 h->chunkfun = (struct _obstack_chunk * (*)(void *,long)) chunkfun;
211 h->freefun = (void (*) (void *, struct _obstack_chunk *)) freefun;
212 h->chunk_size = size;
213 h->alignment_mask = alignment - 1;
214 h->extra_arg = arg;
215 h->use_extra_arg = 1;
216
217 chunk = h->chunk = CALL_CHUNKFUN (h, h -> chunk_size)(((h) -> use_extra_arg) ? (*(h)->chunkfun) ((h)->extra_arg
, (h -> chunk_size)) : (*(struct _obstack_chunk *(*) (long
)) (h)->chunkfun) ((h -> chunk_size)));
218 if (!chunk)
219 (*obstack_alloc_failed_handler) ();
220 h->next_free = h->object_base = __PTR_ALIGN ((char *) chunk, chunk->contents,((sizeof (long int) < sizeof (void *) ? ((char *) chunk) :
(char *) 0) + (((chunk->contents) - (sizeof (long int) <
sizeof (void *) ? ((char *) chunk) : (char *) 0) + (alignment
- 1)) & ~(alignment - 1)))
221 alignment - 1)((sizeof (long int) < sizeof (void *) ? ((char *) chunk) :
(char *) 0) + (((chunk->contents) - (sizeof (long int) <
sizeof (void *) ? ((char *) chunk) : (char *) 0) + (alignment
- 1)) & ~(alignment - 1)));
222 h->chunk_limit = chunk->limit
223 = (char *) chunk + h->chunk_size;
224 chunk->prev = NULL((void*)0);
225 /* The initial chunk now contains no empty object. */
226 h->maybe_empty_object = 0;
227 h->alloc_failed = 0;
228 return 1;
229}
230
231/* Allocate a new current chunk for the obstack *H
232 on the assumption that LENGTH bytes need to be added
233 to the current object, or a new object of length LENGTH allocated.
234 Copies any partial object from the end of the old chunk
235 to the beginning of the new one. */
236
237void
238_obstack_newchunk (struct obstack *h, int length)
239{
240 register struct _obstack_chunk *old_chunk = h->chunk;
241 register struct _obstack_chunk *new_chunk;
242 register long new_size;
243 register long obj_size = h->next_free - h->object_base;
244 register long i;
245 long already;
246 char *object_base;
247
248 /* Compute size for new chunk. */
249 new_size = (obj_size + length) + (obj_size >> 3) + h->alignment_mask + 100;
250 if (new_size < h->chunk_size)
1
Taking false branch
→
251 new_size = h->chunk_size;
252
253 /* Allocate and initialize the new chunk. */
254 new_chunk = CALL_CHUNKFUN (h, new_size)(((h) -> use_extra_arg) ? (*(h)->chunkfun) ((h)->extra_arg
, (new_size)) : (*(struct _obstack_chunk *(*) (long)) (h)->
chunkfun) ((new_size)));
2
←
Value assigned to 'new_chunk'
→
255 if (!new_chunk)
3
←
Assuming 'new_chunk' is null
→
4
←
Taking true branch
→
256 (*obstack_alloc_failed_handler) ();
257 h->chunk = new_chunk;
258 new_chunk->prev = old_chunk;
5
←
Access to field 'prev' results in a dereference of a null pointer (loaded from variable 'new_chunk')
259 new_chunk->limit = h->chunk_limit = (char *) new_chunk + new_size;
260
261 /* Compute an aligned object_base in the new chunk */
262 object_base =
263 __PTR_ALIGN ((char *) new_chunk, new_chunk->contents, h->alignment_mask)((sizeof (long int) < sizeof (void *) ? ((char *) new_chunk
) : (char *) 0) + (((new_chunk->contents) - (sizeof (long int
) < sizeof (void *) ? ((char *) new_chunk) : (char *) 0) +
(h->alignment_mask)) & ~(h->alignment_mask)));
264
265 /* Move the existing object to the new chunk.
266 Word at a time is fast and is safe if the object
267 is sufficiently aligned. */
268 if (h->alignment_mask + 1 >= DEFAULT_ALIGNMENT)
269 {
270 for (i = obj_size / sizeof (COPYING_UNITint) - 1;
271 i >= 0; i--)
272 ((COPYING_UNITint *)object_base)[i]
273 = ((COPYING_UNITint *)h->object_base)[i];
274 /* We used to copy the odd few remaining bytes as one extra COPYING_UNIT,
275 but that can cross a page boundary on a machine
276 which does not do strict alignment for COPYING_UNITS. */
277 already = obj_size / sizeof (COPYING_UNITint) * sizeof (COPYING_UNITint);
278 }
279 else
280 already = 0;
281 /* Copy remaining bytes one by one. */
282 for (i = already; i < obj_size; i++)
283 object_base[i] = h->object_base[i];
284
285 /* If the object just copied was the only data in OLD_CHUNK,
286 free that chunk and remove it from the chain.
287 But not if that chunk might contain an empty object. */
288 if (! h->maybe_empty_object
289 && (h->object_base
290 == __PTR_ALIGN ((char *) old_chunk, old_chunk->contents,((sizeof (long int) < sizeof (void *) ? ((char *) old_chunk
) : (char *) 0) + (((old_chunk->contents) - (sizeof (long int
) < sizeof (void *) ? ((char *) old_chunk) : (char *) 0) +
(h->alignment_mask)) & ~(h->alignment_mask)))
291 h->alignment_mask)((sizeof (long int) < sizeof (void *) ? ((char *) old_chunk
) : (char *) 0) + (((old_chunk->contents) - (sizeof (long int
) < sizeof (void *) ? ((char *) old_chunk) : (char *) 0) +
(h->alignment_mask)) & ~(h->alignment_mask)))))
292 {
293 new_chunk->prev = old_chunk->prev;
294 CALL_FREEFUN (h, old_chunk)do { if ((h) -> use_extra_arg) (*(h)->freefun) ((h)->
extra_arg, (old_chunk)); else (*(void (*) (void *)) (h)->freefun
) ((old_chunk)); } while (0);
295 }
296
297 h->object_base = object_base;
298 h->next_free = h->object_base + obj_size;
299 /* The new chunk certainly contains no empty object yet. */
300 h->maybe_empty_object = 0;
301}
302# ifdef _LIBC
303libc_hidden_def (_obstack_newchunk)
304# endif
305
306/* Return nonzero if object OBJ has been allocated from obstack H.
307 This is here for debugging.
308 If you use it in a program, you are probably losing. */
309
310/* Suppress -Wmissing-prototypes warning. We don't want to declare this in
311 obstack.h because it is just for debugging. */
312int _obstack_allocated_p (struct obstack *h, void *obj);
313
314int
315_obstack_allocated_p (struct obstack *h, void *obj)
316{
317 register struct _obstack_chunk *lp; /* below addr of any objects in this chunk */
318 register struct _obstack_chunk *plp; /* point to previous chunk if any */
319
320 lp = (h)->chunk;
321 /* We use >= rather than > since the object cannot be exactly at
322 the beginning of the chunk but might be an empty object exactly
323 at the end of an adjacent chunk. */
324 while (lp != NULL((void*)0) && ((void *) lp >= obj || (void *) (lp)->limit < obj))
325 {
326 plp = lp->prev;
327 lp = plp;
328 }
329 return lp != NULL((void*)0);
330}
331
332/* Free objects in obstack H, including OBJ and everything allocate
333 more recently than OBJ. If OBJ is zero, free everything in H. */
334
335# undef obstack_free
336
337void
338obstack_free (struct obstack *h, void *obj)
339{
340 register struct _obstack_chunk *lp; /* below addr of any objects in this chunk */
341 register struct _obstack_chunk *plp; /* point to previous chunk if any */
342
343 lp = h->chunk;
344 /* We use >= because there cannot be an object at the beginning of a chunk.
345 But there can be an empty object at that address
346 at the end of another chunk. */
347 while (lp != NULL((void*)0) && ((void *) lp >= obj || (void *) (lp)->limit < obj))
348 {
349 plp = lp->prev;
350 CALL_FREEFUN (h, lp)do { if ((h) -> use_extra_arg) (*(h)->freefun) ((h)->
extra_arg, (lp)); else (*(void (*) (void *)) (h)->freefun)
((lp)); } while (0);
351 lp = plp;
352 /* If we switch chunks, we can't tell whether the new current
353 chunk contains an empty object, so assume that it may. */
354 h->maybe_empty_object = 1;
355 }
356 if (lp)
357 {
358 h->object_base = h->next_free = (char *) (obj);
359 h->chunk_limit = lp->limit;
360 h->chunk = lp;
361 }
362 else if (obj != NULL((void*)0))
363 /* obj is not in any of the chunks! */
364 abort ();
365}
366
367# ifdef _LIBC
368/* Older versions of libc used a function _obstack_free intended to be
369 called by non-GCC compilers. */
370strong_alias (obstack_free, _obstack_free)
371# endif
372
373int
374_obstack_memory_used (struct obstack *h)
375{
376 register struct _obstack_chunk* lp;
377 register int nbytes = 0;
378
379 for (lp = h->chunk; lp != NULL((void*)0); lp = lp->prev)
380 {
381 nbytes += lp->limit - (char *) lp;
382 }
383 return nbytes;
384}
385
386# ifdef _LIBC
387# include <libio/iolibio.h>
388# endif
389
390# ifndef __attribute__
391/* This feature is available in gcc versions 2.5 and later. */
392# if __GNUC__4 < 2 || (__GNUC__4 == 2 && __GNUC_MINOR__2 < 5)
393# define __attribute__(Spec) /* empty */
394# endif
395# endif
396
397static void
398print_and_abort (void)
399{
400 /* Don't change any of these strings. Yes, it would be possible to add
401 the newline to the string and use fputs or so. But this must not
402 happen because the "memory exhausted" message appears in other places
403 like this and the translation should be reused instead of creating
404 a very similar string which requires a separate translation. */
405# ifdef _LIBC
406 (void) __fxprintf (NULL((void*)0), "%s\n", _("memory exhausted"));
407# else
408 fprintf (stderr__stderrp, "%s\n", _("memory exhausted"));
409# endif
410 exit (1);
411}
412
413#endif /* !ELIDE_CODE */