diff options
Diffstat (limited to 'lib/allocsa.c')
| -rw-r--r-- | lib/allocsa.c | 137 |
1 files changed, 0 insertions, 137 deletions
diff --git a/lib/allocsa.c b/lib/allocsa.c deleted file mode 100644 index 97652e6..0000000 --- a/lib/allocsa.c +++ /dev/null @@ -1,137 +0,0 @@ -/* Safe automatic memory allocation. - Copyright (C) 2003, 2006 Free Software Foundation, Inc. - Written by Bruno Haible <bruno@clisp.org>, 2003. - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2, or (at your option) - any later version. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software Foundation, - Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ - -#include <config.h> - -/* Specification. */ -#include "allocsa.h" - -/* The speed critical point in this file is freesa() applied to an alloca() - result: it must be fast, to match the speed of alloca(). The speed of - mallocsa() and freesa() in the other case are not critical, because they - are only invoked for big memory sizes. */ - -#if HAVE_ALLOCA - -/* Store the mallocsa() results in a hash table. This is needed to reliably - distinguish a mallocsa() result and an alloca() result. - - Although it is possible that the same pointer is returned by alloca() and - by mallocsa() at different times in the same application, it does not lead - to a bug in freesa(), because: - - Before a pointer returned by alloca() can point into malloc()ed memory, - the function must return, and once this has happened the programmer must - not call freesa() on it anyway. - - Before a pointer returned by mallocsa() can point into the stack, it - must be freed. The only function that can free it is freesa(), and - when freesa() frees it, it also removes it from the hash table. */ - -#define MAGIC_NUMBER 0x1415fb4a -#define MAGIC_SIZE sizeof (int) -/* This is how the header info would look like without any alignment - considerations. */ -struct preliminary_header { void *next; char room[MAGIC_SIZE]; }; -/* But the header's size must be a multiple of sa_alignment_max. */ -#define HEADER_SIZE \ - (((sizeof (struct preliminary_header) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max) -struct header { void *next; char room[HEADER_SIZE - sizeof (struct preliminary_header) + MAGIC_SIZE]; }; -/* Verify that HEADER_SIZE == sizeof (struct header). */ -typedef int verify1[2 * (HEADER_SIZE == sizeof (struct header)) - 1]; -/* We make the hash table quite big, so that during lookups the probability - of empty hash buckets is quite high. There is no need to make the hash - table resizable, because when the hash table gets filled so much that the - lookup becomes slow, it means that the application has memory leaks. */ -#define HASH_TABLE_SIZE 257 -static void * mallocsa_results[HASH_TABLE_SIZE]; - -#endif - -void * -mallocsa (size_t n) -{ -#if HAVE_ALLOCA - /* Allocate one more word, that serves as an indicator for malloc()ed - memory, so that freesa() of an alloca() result is fast. */ - size_t nplus = n + HEADER_SIZE; - - if (nplus >= n) - { - char *p = (char *) malloc (nplus); - - if (p != NULL) - { - size_t slot; - - p += HEADER_SIZE; - - /* Put a magic number into the indicator word. */ - ((int *) p)[-1] = MAGIC_NUMBER; - - /* Enter p into the hash table. */ - slot = (unsigned long) p % HASH_TABLE_SIZE; - ((struct header *) (p - HEADER_SIZE))->next = mallocsa_results[slot]; - mallocsa_results[slot] = p; - - return p; - } - } - /* Out of memory. */ - return NULL; -#else -# if !MALLOC_0_IS_NONNULL - if (n == 0) - n = 1; -# endif - return malloc (n); -#endif -} - -#if HAVE_ALLOCA -void -freesa (void *p) -{ - /* mallocsa() may have returned NULL. */ - if (p != NULL) - { - /* Attempt to quickly distinguish the mallocsa() result - which has - a magic indicator word - and the alloca() result - which has an - uninitialized indicator word. It is for this test that sa_increment - additional bytes are allocated in the alloca() case. */ - if (((int *) p)[-1] == MAGIC_NUMBER) - { - /* Looks like a mallocsa() result. To see whether it really is one, - perform a lookup in the hash table. */ - size_t slot = (unsigned long) p % HASH_TABLE_SIZE; - void **chain = &mallocsa_results[slot]; - for (; *chain != NULL;) - { - if (*chain == p) - { - /* Found it. Remove it from the hash table and free it. */ - char *p_begin = (char *) p - HEADER_SIZE; - *chain = ((struct header *) p_begin)->next; - free (p_begin); - return; - } - chain = &((struct header *) ((char *) *chain - HEADER_SIZE))->next; - } - } - /* At this point, we know it was not a mallocsa() result. */ - } -} -#endif |