New upstream version 2.3.4
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556 changed files with 90432 additions and 53391 deletions
163
gl/malloca.c
163
gl/malloca.c
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/* Safe automatic memory allocation.
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Copyright (C) 2003, 2006-2007, 2009-2013 Free Software Foundation, Inc.
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Written by Bruno Haible <bruno@clisp.org>, 2003.
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Copyright (C) 2003, 2006-2007, 2009-2023 Free Software Foundation, Inc.
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Written by Bruno Haible <bruno@clisp.org>, 2003, 2018.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <http://www.gnu.org/licenses/>. */
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#define _GL_USE_STDLIB_ALLOC 1
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#include <config.h>
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@ -21,82 +21,56 @@
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/* Specification. */
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#include "malloca.h"
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#include <stdint.h>
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#include <stdckdint.h>
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#include "verify.h"
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#include "idx.h"
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/* The speed critical point in this file is freea() applied to an alloca()
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result: it must be fast, to match the speed of alloca(). The speed of
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mmalloca() and freea() in the other case are not critical, because they
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are only invoked for big memory sizes. */
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are only invoked for big memory sizes.
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Here we use a bit in the address as an indicator, an idea by Ondřej Bílka.
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malloca() can return three types of pointers:
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- Pointers ≡ 0 mod 2*sa_alignment_max come from stack allocation.
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- Pointers ≡ sa_alignment_max mod 2*sa_alignment_max come from heap
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allocation.
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- NULL comes from a failed heap allocation. */
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#if HAVE_ALLOCA
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/* Store the mmalloca() results in a hash table. This is needed to reliably
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distinguish a mmalloca() result and an alloca() result.
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Although it is possible that the same pointer is returned by alloca() and
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by mmalloca() at different times in the same application, it does not lead
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to a bug in freea(), because:
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- Before a pointer returned by alloca() can point into malloc()ed memory,
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the function must return, and once this has happened the programmer must
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not call freea() on it anyway.
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- Before a pointer returned by mmalloca() can point into the stack, it
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must be freed. The only function that can free it is freea(), and
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when freea() frees it, it also removes it from the hash table. */
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#define MAGIC_NUMBER 0x1415fb4a
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#define MAGIC_SIZE sizeof (int)
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/* This is how the header info would look like without any alignment
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considerations. */
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struct preliminary_header { void *next; int magic; };
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/* But the header's size must be a multiple of sa_alignment_max. */
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#define HEADER_SIZE \
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(((sizeof (struct preliminary_header) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max)
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union header {
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void *next;
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struct {
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char room[HEADER_SIZE - MAGIC_SIZE];
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int word;
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} magic;
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};
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verify (HEADER_SIZE == sizeof (union header));
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/* We make the hash table quite big, so that during lookups the probability
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of empty hash buckets is quite high. There is no need to make the hash
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table resizable, because when the hash table gets filled so much that the
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lookup becomes slow, it means that the application has memory leaks. */
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#define HASH_TABLE_SIZE 257
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static void * mmalloca_results[HASH_TABLE_SIZE];
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#endif
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/* Type for holding very small pointer differences. */
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typedef unsigned char small_t;
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/* Verify that it is wide enough. */
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static_assert (2 * sa_alignment_max - 1 <= (small_t) -1);
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void *
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mmalloca (size_t n)
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{
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#if HAVE_ALLOCA
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/* Allocate one more word, that serves as an indicator for malloc()ed
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memory, so that freea() of an alloca() result is fast. */
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size_t nplus = n + HEADER_SIZE;
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if (nplus >= n)
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/* Allocate one more word, used to determine the address to pass to freea(),
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and room for the alignment ≡ sa_alignment_max mod 2*sa_alignment_max. */
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uintptr_t alignment2_mask = 2 * sa_alignment_max - 1;
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int plus = sizeof (small_t) + alignment2_mask;
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idx_t nplus;
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if (!ckd_add (&nplus, n, plus) && !xalloc_oversized (nplus, 1))
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{
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void *p = malloc (nplus);
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char *mem = (char *) malloc (nplus);
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if (p != NULL)
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if (mem != NULL)
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{
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size_t slot;
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union header *h = p;
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p = h + 1;
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/* Put a magic number into the indicator word. */
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h->magic.word = MAGIC_NUMBER;
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/* Enter p into the hash table. */
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slot = (uintptr_t) p % HASH_TABLE_SIZE;
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h->next = mmalloca_results[slot];
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mmalloca_results[slot] = p;
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uintptr_t umem = (uintptr_t)mem, umemplus;
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/* The ckd_add avoids signed integer overflow on
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theoretical platforms where UINTPTR_MAX <= INT_MAX. */
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ckd_add (&umemplus, umem, sizeof (small_t) + sa_alignment_max - 1);
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idx_t offset = ((umemplus & ~alignment2_mask)
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+ sa_alignment_max - umem);
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void *vp = mem + offset;
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small_t *p = vp;
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/* Here p >= mem + sizeof (small_t),
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and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1
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hence p + n <= mem + nplus.
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So, the memory range [p, p+n) lies in the allocated memory range
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[mem, mem + nplus). */
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p[-1] = offset;
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/* p ≡ sa_alignment_max mod 2*sa_alignment_max. */
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return p;
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}
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}
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@ -115,35 +89,24 @@ mmalloca (size_t n)
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void
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freea (void *p)
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{
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/* mmalloca() may have returned NULL. */
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if (p != NULL)
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/* Check argument. */
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if ((uintptr_t) p & (sa_alignment_max - 1))
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{
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/* Attempt to quickly distinguish the mmalloca() result - which has
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a magic indicator word - and the alloca() result - which has an
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uninitialized indicator word. It is for this test that sa_increment
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additional bytes are allocated in the alloca() case. */
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if (((int *) p)[-1] == MAGIC_NUMBER)
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{
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/* Looks like a mmalloca() result. To see whether it really is one,
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perform a lookup in the hash table. */
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size_t slot = (uintptr_t) p % HASH_TABLE_SIZE;
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void **chain = &mmalloca_results[slot];
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for (; *chain != NULL;)
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{
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union header *h = p;
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if (*chain == p)
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{
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/* Found it. Remove it from the hash table and free it. */
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union header *p_begin = h - 1;
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*chain = p_begin->next;
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free (p_begin);
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return;
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}
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h = *chain;
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chain = &h[-1].next;
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}
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}
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/* At this point, we know it was not a mmalloca() result. */
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/* p was not the result of a malloca() call. Invalid argument. */
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abort ();
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}
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/* Determine whether p was a non-NULL pointer returned by mmalloca(). */
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if ((uintptr_t) p & sa_alignment_max)
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{
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void *mem = (char *) p - ((small_t *) p)[-1];
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free (mem);
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}
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}
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#endif
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/*
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* Hey Emacs!
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* Local Variables:
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* coding: utf-8
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* End:
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*/
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