| File: | gl/malloca.c |
| Warning: | line 65, column 31 Potential leak of memory pointed to by 'mem' |
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| 1 | /* Safe automatic memory allocation. | |||
| 2 | Copyright (C) 2003, 2006-2007, 2009-2020 Free Software Foundation, Inc. | |||
| 3 | Written by Bruno Haible <bruno@clisp.org>, 2003, 2018. | |||
| 4 | ||||
| 5 | This program is free software; you can redistribute it and/or modify | |||
| 6 | it under the terms of the GNU General Public License as published by | |||
| 7 | the Free Software Foundation; either version 3, or (at your option) | |||
| 8 | any later version. | |||
| 9 | ||||
| 10 | This program is distributed in the hope that it will be useful, | |||
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |||
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |||
| 13 | GNU General Public License for more details. | |||
| 14 | ||||
| 15 | You should have received a copy of the GNU General Public License | |||
| 16 | along with this program; if not, see <https://www.gnu.org/licenses/>. */ | |||
| 17 | ||||
| 18 | #define _GL_USE_STDLIB_ALLOC1 1 | |||
| 19 | #include <config.h> | |||
| 20 | ||||
| 21 | /* Specification. */ | |||
| 22 | #include "malloca.h" | |||
| 23 | ||||
| 24 | #include "verify.h" | |||
| 25 | ||||
| 26 | /* The speed critical point in this file is freea() applied to an alloca() | |||
| 27 | result: it must be fast, to match the speed of alloca(). The speed of | |||
| 28 | mmalloca() and freea() in the other case are not critical, because they | |||
| 29 | are only invoked for big memory sizes. | |||
| 30 | Here we use a bit in the address as an indicator, an idea by Ondřej Bílka. | |||
| 31 | malloca() can return three types of pointers: | |||
| 32 | - Pointers ≡ 0 mod 2*sa_alignment_max come from stack allocation. | |||
| 33 | - Pointers ≡ sa_alignment_max mod 2*sa_alignment_max come from heap | |||
| 34 | allocation. | |||
| 35 | - NULL comes from a failed heap allocation. */ | |||
| 36 | ||||
| 37 | /* Type for holding very small pointer differences. */ | |||
| 38 | typedef unsigned char small_t; | |||
| 39 | /* Verify that it is wide enough. */ | |||
| 40 | verify (2 * sa_alignment_max - 1 <= (small_t) -1)_Static_assert (2 * sa_alignment_max - 1 <= (small_t) -1, "verify (" "2 * sa_alignment_max - 1 <= (small_t) -1" ")"); | |||
| 41 | ||||
| 42 | void * | |||
| 43 | mmalloca (size_t n) | |||
| 44 | { | |||
| 45 | #if HAVE_ALLOCA1 | |||
| 46 | /* Allocate one more word, used to determine the address to pass to freea(), | |||
| 47 | and room for the alignment ≡ sa_alignment_max mod 2*sa_alignment_max. */ | |||
| 48 | size_t nplus = n + sizeof (small_t) + 2 * sa_alignment_max - 1; | |||
| 49 | ||||
| 50 | if (nplus >= n) | |||
| ||||
| 51 | { | |||
| 52 | char *mem = (char *) malloc (nplus); | |||
| 53 | ||||
| 54 | if (mem != NULL((void*)0)) | |||
| 55 | { | |||
| 56 | char *p = | |||
| 57 | (char *)((((uintptr_t)mem + sizeof (small_t) + sa_alignment_max - 1) | |||
| 58 | & ~(uintptr_t)(2 * sa_alignment_max - 1)) | |||
| 59 | + sa_alignment_max); | |||
| 60 | /* Here p >= mem + sizeof (small_t), | |||
| 61 | and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1 | |||
| 62 | hence p + n <= mem + nplus. | |||
| 63 | So, the memory range [p, p+n) lies in the allocated memory range | |||
| 64 | [mem, mem + nplus). */ | |||
| 65 | ((small_t *) p)[-1] = p - mem; | |||
| ||||
| 66 | /* p ≡ sa_alignment_max mod 2*sa_alignment_max. */ | |||
| 67 | return p; | |||
| 68 | } | |||
| 69 | } | |||
| 70 | /* Out of memory. */ | |||
| 71 | return NULL((void*)0); | |||
| 72 | #else | |||
| 73 | # if !MALLOC_0_IS_NONNULL1 | |||
| 74 | if (n == 0) | |||
| 75 | n = 1; | |||
| 76 | # endif | |||
| 77 | return malloc (n); | |||
| 78 | #endif | |||
| 79 | } | |||
| 80 | ||||
| 81 | #if HAVE_ALLOCA1 | |||
| 82 | void | |||
| 83 | freea (void *p) | |||
| 84 | { | |||
| 85 | /* Check argument. */ | |||
| 86 | if ((uintptr_t) p & (sa_alignment_max - 1)) | |||
| 87 | { | |||
| 88 | /* p was not the result of a malloca() call. Invalid argument. */ | |||
| 89 | abort (); | |||
| 90 | } | |||
| 91 | /* Determine whether p was a non-NULL pointer returned by mmalloca(). */ | |||
| 92 | if ((uintptr_t) p & sa_alignment_max) | |||
| 93 | { | |||
| 94 | void *mem = (char *) p - ((small_t *) p)[-1]; | |||
| 95 | free (mem); | |||
| 96 | } | |||
| 97 | } | |||
| 98 | #endif | |||
| 99 | ||||
| 100 | /* | |||
| 101 | * Hey Emacs! | |||
| 102 | * Local Variables: | |||
| 103 | * coding: utf-8 | |||
| 104 | * End: | |||
| 105 | */ |