summaryrefslogtreecommitdiffstats
path: root/gl/malloca.c
diff options
context:
space:
mode:
Diffstat (limited to 'gl/malloca.c')
-rw-r--r--gl/malloca.c45
1 files changed, 27 insertions, 18 deletions
diff --git a/gl/malloca.c b/gl/malloca.c
index 21bbc1f5..311be569 100644
--- a/gl/malloca.c
+++ b/gl/malloca.c
@@ -1,5 +1,5 @@
1/* Safe automatic memory allocation. 1/* Safe automatic memory allocation.
2 Copyright (C) 2003, 2006-2007, 2009-2010 Free Software Foundation, Inc. 2 Copyright (C) 2003, 2006-2007, 2009-2013 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2003. 3 Written by Bruno Haible <bruno@clisp.org>, 2003.
4 4
5 This program is free software; you can redistribute it and/or modify 5 This program is free software; you can redistribute it and/or modify
@@ -13,16 +13,17 @@
13 GNU General Public License for more details. 13 GNU General Public License for more details.
14 14
15 You should have received a copy of the GNU General Public License 15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation, 16 along with this program; if not, see <http://www.gnu.org/licenses/>. */
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 17
18#define _GL_USE_STDLIB_ALLOC 1
19#include <config.h> 19#include <config.h>
20 20
21/* Specification. */ 21/* Specification. */
22#include "malloca.h" 22#include "malloca.h"
23 23
24/* Use the system functions, not the gnulib overrides in this file. */ 24#include <stdint.h>
25#undef malloc 25
26#include "verify.h"
26 27
27/* The speed critical point in this file is freea() applied to an alloca() 28/* The speed critical point in this file is freea() applied to an alloca()
28 result: it must be fast, to match the speed of alloca(). The speed of 29 result: it must be fast, to match the speed of alloca(). The speed of
@@ -48,13 +49,18 @@
48#define MAGIC_SIZE sizeof (int) 49#define MAGIC_SIZE sizeof (int)
49/* This is how the header info would look like without any alignment 50/* This is how the header info would look like without any alignment
50 considerations. */ 51 considerations. */
51struct preliminary_header { void *next; char room[MAGIC_SIZE]; }; 52struct preliminary_header { void *next; int magic; };
52/* But the header's size must be a multiple of sa_alignment_max. */ 53/* But the header's size must be a multiple of sa_alignment_max. */
53#define HEADER_SIZE \ 54#define HEADER_SIZE \
54 (((sizeof (struct preliminary_header) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max) 55 (((sizeof (struct preliminary_header) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max)
55struct header { void *next; char room[HEADER_SIZE - sizeof (struct preliminary_header) + MAGIC_SIZE]; }; 56union header {
56/* Verify that HEADER_SIZE == sizeof (struct header). */ 57 void *next;
57typedef int verify1[2 * (HEADER_SIZE == sizeof (struct header)) - 1]; 58 struct {
59 char room[HEADER_SIZE - MAGIC_SIZE];
60 int word;
61 } magic;
62};
63verify (HEADER_SIZE == sizeof (union header));
58/* We make the hash table quite big, so that during lookups the probability 64/* We make the hash table quite big, so that during lookups the probability
59 of empty hash buckets is quite high. There is no need to make the hash 65 of empty hash buckets is quite high. There is no need to make the hash
60 table resizable, because when the hash table gets filled so much that the 66 table resizable, because when the hash table gets filled so much that the
@@ -74,20 +80,21 @@ mmalloca (size_t n)
74 80
75 if (nplus >= n) 81 if (nplus >= n)
76 { 82 {
77 char *p = (char *) malloc (nplus); 83 void *p = malloc (nplus);
78 84
79 if (p != NULL) 85 if (p != NULL)
80 { 86 {
81 size_t slot; 87 size_t slot;
88 union header *h = p;
82 89
83 p += HEADER_SIZE; 90 p = h + 1;
84 91
85 /* Put a magic number into the indicator word. */ 92 /* Put a magic number into the indicator word. */
86 ((int *) p)[-1] = MAGIC_NUMBER; 93 h->magic.word = MAGIC_NUMBER;
87 94
88 /* Enter p into the hash table. */ 95 /* Enter p into the hash table. */
89 slot = (unsigned long) p % HASH_TABLE_SIZE; 96 slot = (uintptr_t) p % HASH_TABLE_SIZE;
90 ((struct header *) (p - HEADER_SIZE))->next = mmalloca_results[slot]; 97 h->next = mmalloca_results[slot];
91 mmalloca_results[slot] = p; 98 mmalloca_results[slot] = p;
92 99
93 return p; 100 return p;
@@ -119,19 +126,21 @@ freea (void *p)
119 { 126 {
120 /* Looks like a mmalloca() result. To see whether it really is one, 127 /* Looks like a mmalloca() result. To see whether it really is one,
121 perform a lookup in the hash table. */ 128 perform a lookup in the hash table. */
122 size_t slot = (unsigned long) p % HASH_TABLE_SIZE; 129 size_t slot = (uintptr_t) p % HASH_TABLE_SIZE;
123 void **chain = &mmalloca_results[slot]; 130 void **chain = &mmalloca_results[slot];
124 for (; *chain != NULL;) 131 for (; *chain != NULL;)
125 { 132 {
133 union header *h = p;
126 if (*chain == p) 134 if (*chain == p)
127 { 135 {
128 /* Found it. Remove it from the hash table and free it. */ 136 /* Found it. Remove it from the hash table and free it. */
129 char *p_begin = (char *) p - HEADER_SIZE; 137 union header *p_begin = h - 1;
130 *chain = ((struct header *) p_begin)->next; 138 *chain = p_begin->next;
131 free (p_begin); 139 free (p_begin);
132 return; 140 return;
133 } 141 }
134 chain = &((struct header *) ((char *) *chain - HEADER_SIZE))->next; 142 h = *chain;
143 chain = &h[-1].next;
135 } 144 }
136 } 145 }
137 /* At this point, we know it was not a mmalloca() result. */ 146 /* At this point, we know it was not a mmalloca() result. */