gnulib: lib/malloca.c annotate

annotate lib/malloca.c @ 39235:6a04b04905e5

malloca, xmalloca: Make multithread-safe. Reported by Florian Weimer <fweimer@redhat.com>. Implements an idea by Ondřej Bílka <neleai@seznam.cz>. * lib/malloca.h (malloca): In the stack allocation case, return a pointer that is a multiple of 2 * sa_alignment_max. (sa_increment): Remove enum item. * lib/xmalloca.h (xmalloca): In the stack allocation case, return a pointer that is a multiple of 2 * sa_alignment_max. * lib/malloca.c (NO_SANITIZE_MEMORY): Remove macro. (MAGIC_NUMBER, MAGIC_SIZE, preliminary_header, HEADER_SIZE, header, HASH_TABLE_SIZE, mmalloca_results): Remove. (small_t): New type. (mmalloca, free): Rewritten. * lib/malloca.valgrind: Remove file. * modules/malloca (Files): Remove it. (Depends-on): Remove verify.

author	Bruno Haible <bruno@clisp.org>
date	Fri, 02 Feb 2018 19:32:02 +0100
parents	24e347e0e326
children	fc9a55e09027

rev	line source
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	1 /* Safe automatic memory allocation.
39199 24e347e0e326 maint: Run 'make update-copyright' Paul Eggert <eggert@cs.ucla.edu> parents: 38844 diff changeset	2 Copyright (C) 2003, 2006-2007, 2009-2018 Free Software Foundation, Inc.
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	3 Written by Bruno Haible <bruno@clisp.org>, 2003, 2018.
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	4
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	5 This program is free software; you can redistribute it and/or modify
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	6 it under the terms of the GNU General Public License as published by
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	7 the Free Software Foundation; either version 2, or (at your option)
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	8 any later version.
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	9
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	10 This program is distributed in the hope that it will be useful,
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	11 but WITHOUT ANY WARRANTY; without even the implied warranty of
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	13 GNU General Public License for more details.
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	14
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	15 You should have received a copy of the GNU General Public License
38844 a8586d5e30d2 all: prefer https: URLs Paul Eggert <eggert@cs.ucla.edu> parents: 38683 diff changeset	16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	17
34231 39cd7b3c3f75 * lib/malloca.c (_GL_USE_STDLIB_ALLOC, malloc): Likewise. Paul Eggert <eggert@cs.ucla.edu> parents: 33770 diff changeset	18 #define _GL_USE_STDLIB_ALLOC 1
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	19 #include <config.h>
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	20
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	21 /* Specification. */
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	22 #include "malloca.h"
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	23
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	24 /* The speed critical point in this file is freea() applied to an alloca()
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	25 result: it must be fast, to match the speed of alloca(). The speed of
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	26 mmalloca() and freea() in the other case are not critical, because they
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	27 are only invoked for big memory sizes.
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	28 Here we use a bit in the address as an indicator, an idea by Ondřej Bílka.
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	29 malloca() can return three types of pointers:
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	30 - Pointers ≡ 0 mod 2*sa_alignment_max come from stack allocation.
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	31 - Pointers ≡ sa_alignment_max mod 2*sa_alignment_max come from heap
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	32 allocation.
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	33 - NULL comes from a failed heap allocation. */
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	34
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	35 /* Type for holding very small pointer differences. */
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	36 typedef unsigned char small_t;
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	37
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	38 void *
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	39 mmalloca (size_t n)
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	40 {
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	41 #if HAVE_ALLOCA
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	42 /* Allocate one more word, used to determine the address to pass to freea(),
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	43 and room for the alignment ≡ sa_alignment_max mod 2sa_alignment_max. /
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	44 size_t nplus = n + sizeof (small_t) + 2 * sa_alignment_max - 1;
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	45
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	46 if (nplus >= n)
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	47 {
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	48 char mem = (char ) malloc (nplus);
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	49
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	50 if (mem != NULL)
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	51 {
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	52 char *p =
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	53 (char *)((((uintptr_t)mem + sizeof (small_t) + sa_alignment_max - 1)
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	54 & ~(uintptr_t)(2 * sa_alignment_max - 1))
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	55 + sa_alignment_max);
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	56 /* Here p >= mem + sizeof (small_t),
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	57 and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	58 hence p + n <= mem + nplus.
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	59 So, the memory range [p, p+n) lies in the allocated memory range
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	60 [mem, mem + nplus). */
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	61 ((small_t *) p)[-1] = p - mem;
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	62 /* p ≡ sa_alignment_max mod 2sa_alignment_max. /
32112 dc7644a1c024 Use spaces for indentation, not tabs. Bruno Haible <bruno@clisp.org> parents: 28623 diff changeset	63 return p;
dc7644a1c024 Use spaces for indentation, not tabs. Bruno Haible <bruno@clisp.org> parents: 28623 diff changeset	64 }
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	65 }
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	66 /* Out of memory. */
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	67 return NULL;
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	68 #else
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	69 # if !MALLOC_0_IS_NONNULL
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	70 if (n == 0)
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	71 n = 1;
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	72 # endif
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	73 return malloc (n);
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	74 #endif
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	75 }
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	76
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	77 #if HAVE_ALLOCA
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	78 void
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	79 freea (void *p)
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	80 {
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	81 /* Determine whether p was a non-NULL pointer returned by mmalloca(). */
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	82 if ((uintptr_t) p & sa_alignment_max)
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	83 {
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	84 void mem = (char ) p - ((small_t *) p)[-1];
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	85 free (mem);
28623 227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	86 }
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	87 }
227e2944ac3f Move to here from allocsa.c. Bruno Haible <bruno@clisp.org> parents: diff changeset	88 #endif
39235 6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	89
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	90 /*
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	91 * Hey Emacs!
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	92 * Local Variables:
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	93 * coding: utf-8
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	94 * End:
6a04b04905e5 malloca, xmalloca: Make multithread-safe. Bruno Haible <bruno@clisp.org> parents: 39199 diff changeset	95 */

Mercurial > gnulib

annotate lib/malloca.c @ 39235:6a04b04905e5