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Annotation of mandoc/compat_recallocarray.c, Revision 1.1

1.1     ! schwarze    1: #include "config.h"
        !             2:
        !             3: #if HAVE_RECALLOCARRAY
        !             4:
        !             5: int dummy;
        !             6:
        !             7: #else
        !             8:
        !             9: /*     $Id: compat_reallocarray.c,v 1.4 2014/12/11 09:05:01 schwarze Exp $ */
        !            10: /*     $OpenBSD: malloc.c,v 1.225 2017/05/13 07:11:29 otto Exp $ */
        !            11: /*
        !            12:  * Copyright (c) 2017 Otto Moerbeek <otto@drijf.net>
        !            13:  *
        !            14:  * Permission to use, copy, modify, and distribute this software for any
        !            15:  * purpose with or without fee is hereby granted, provided that the above
        !            16:  * copyright notice and this permission notice appear in all copies.
        !            17:  *
        !            18:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
        !            19:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
        !            20:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
        !            21:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
        !            22:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
        !            23:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
        !            24:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
        !            25:  */
        !            26:
        !            27: #include <sys/types.h>
        !            28: #include <errno.h>
        !            29: #include <stdint.h>
        !            30: #include <stdlib.h>
        !            31: #include <string.h>
        !            32:
        !            33: /*
        !            34:  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
        !            35:  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
        !            36:  */
        !            37: #define MUL_NO_OVERFLOW        ((size_t)1 << (sizeof(size_t) * 4))
        !            38:
        !            39: /*
        !            40:  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
        !            41:  * macros have very poor portability.  Since we only use this
        !            42:  * to avoid free() overhead for small shrinking, simply pick
        !            43:  * an arbitrary number.
        !            44:  */
        !            45: #define MALLOC_PAGESIZE         (1UL << 12)
        !            46:
        !            47:
        !            48: void *
        !            49: recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
        !            50: {
        !            51:        size_t oldsize, newsize;
        !            52:        void *newptr;
        !            53:
        !            54:        if (ptr == NULL)
        !            55:                return calloc(newnmemb, size);
        !            56:
        !            57:        if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
        !            58:            newnmemb > 0 && SIZE_MAX / newnmemb < size) {
        !            59:                errno = ENOMEM;
        !            60:                return NULL;
        !            61:        }
        !            62:        newsize = newnmemb * size;
        !            63:
        !            64:        if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
        !            65:            oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
        !            66:                errno = EINVAL;
        !            67:                return NULL;
        !            68:        }
        !            69:        oldsize = oldnmemb * size;
        !            70:
        !            71:        /*
        !            72:         * Don't bother too much if we're shrinking just a bit,
        !            73:         * we do not shrink for series of small steps, oh well.
        !            74:         */
        !            75:        if (newsize <= oldsize) {
        !            76:                size_t d = oldsize - newsize;
        !            77:
        !            78:                if (d < oldsize / 2 && d < MALLOC_PAGESIZE) {
        !            79:                        memset((char *)ptr + newsize, 0, d);
        !            80:                        return ptr;
        !            81:                }
        !            82:        }
        !            83:
        !            84:        newptr = malloc(newsize);
        !            85:        if (newptr == NULL)
        !            86:                return NULL;
        !            87:
        !            88:        if (newsize > oldsize) {
        !            89:                memcpy(newptr, ptr, oldsize);
        !            90:                memset((char *)newptr + oldsize, 0, newsize - oldsize);
        !            91:        } else
        !            92:                memcpy(newptr, ptr, newsize);
        !            93:
        !            94:        /*
        !            95:         * At this point, the OpenBSD implementation calls
        !            96:         * explicit_bzero() on the old memory before it is
        !            97:         * freed.  Since explicit_bzero() is hard to implement
        !            98:         * portably and we don't handle confidential data in
        !            99:         * mandoc in the first place, simply free the memory
        !           100:         * without clearing it.
        !           101:         */
        !           102:
        !           103:        free(ptr);
        !           104:
        !           105:        return newptr;
        !           106: }
        !           107:
        !           108: #endif /* !HAVE_RECALLOCARRAY */