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128 lines
4.4 KiB
128 lines
4.4 KiB
/* Safe automatic memory allocation. |
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Copyright (C) 2003-2007, 2009-2017 Free Software Foundation, Inc. |
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Written by Bruno Haible <bruno@clisp.org>, 2003. |
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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 program 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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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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#ifndef _MALLOCA_H |
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#define _MALLOCA_H |
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#include <alloca.h> |
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#include <stddef.h> |
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#include <stdlib.h> |
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#include <stdint.h> |
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#include "xalloc-oversized.h" |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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/* safe_alloca(N) is equivalent to alloca(N) when it is safe to call |
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alloca(N); otherwise it returns NULL. It either returns N bytes of |
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memory allocated on the stack, that lasts until the function returns, |
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or NULL. |
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Use of safe_alloca should be avoided: |
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- inside arguments of function calls - undefined behaviour, |
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- in inline functions - the allocation may actually last until the |
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calling function returns. |
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*/ |
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#if HAVE_ALLOCA |
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/* The OS usually guarantees only one guard page at the bottom of the stack, |
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and a page size can be as small as 4096 bytes. So we cannot safely |
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allocate anything larger than 4096 bytes. Also care for the possibility |
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of a few compiler-allocated temporary stack slots. |
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This must be a macro, not a function. */ |
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# define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL) |
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#else |
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# define safe_alloca(N) ((void) (N), NULL) |
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#endif |
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/* malloca(N) is a safe variant of alloca(N). It allocates N bytes of |
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memory allocated on the stack, that must be freed using freea() before |
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the function returns. Upon failure, it returns NULL. */ |
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#if HAVE_ALLOCA |
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# define malloca(N) \ |
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((N) < 4032 - sa_increment \ |
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? (void *) ((char *) alloca ((N) + sa_increment) + sa_increment) \ |
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: mmalloca (N)) |
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#else |
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# define malloca(N) \ |
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mmalloca (N) |
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#endif |
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extern void * mmalloca (size_t n); |
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/* Free a block of memory allocated through malloca(). */ |
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#if HAVE_ALLOCA |
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extern void freea (void *p); |
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#else |
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# define freea free |
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#endif |
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/* nmalloca(N,S) is an overflow-safe variant of malloca (N * S). |
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It allocates an array of N objects, each with S bytes of memory, |
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on the stack. S must be positive and N must be nonnegative. |
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The array must be freed using freea() before the function returns. */ |
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#define nmalloca(n, s) (xalloc_oversized (n, s) ? NULL : malloca ((n) * (s))) |
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#ifdef __cplusplus |
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} |
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#endif |
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/* ------------------- Auxiliary, non-public definitions ------------------- */ |
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/* Determine the alignment of a type at compile time. */ |
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#if defined __GNUC__ || defined __IBM__ALIGNOF__ |
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# define sa_alignof __alignof__ |
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#elif defined __cplusplus |
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template <class type> struct sa_alignof_helper { char __slot1; type __slot2; }; |
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# define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2) |
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#elif defined __hpux |
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/* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof |
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values. */ |
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# define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8) |
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#elif defined _AIX |
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/* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof |
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values. */ |
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# define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8) |
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#else |
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# define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) |
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#endif |
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enum |
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{ |
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/* The desired alignment of memory allocations is the maximum alignment |
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among all elementary types. */ |
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sa_alignment_long = sa_alignof (long), |
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sa_alignment_double = sa_alignof (double), |
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#if HAVE_LONG_LONG_INT |
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sa_alignment_longlong = sa_alignof (long long), |
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#endif |
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sa_alignment_longdouble = sa_alignof (long double), |
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sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1) |
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#if HAVE_LONG_LONG_INT |
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| (sa_alignment_longlong - 1) |
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#endif |
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| (sa_alignment_longdouble - 1) |
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) + 1, |
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/* The increment that guarantees room for a magic word must be >= sizeof (int) |
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and a multiple of sa_alignment_max. */ |
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sa_increment = ((sizeof (int) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max |
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}; |
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#endif /* _MALLOCA_H */
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