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120 lines
3.8 KiB
C
120 lines
3.8 KiB
C
/* Memory allocation with expensive empty allocations.
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Copyright (C) 2003, 2008, 2010-2025 Free Software Foundation, Inc.
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Written by Bruno Haible <bruno@clisp.org>, 2003,
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based on prior work by Jim Meyering.
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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 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 Lesser General Public License for more details.
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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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#ifndef _EEALLOC_H
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#define _EEALLOC_H
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/* malloc (0) and realloc (NULL, 0) can return NULL even when memory
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is available; see ISO C 23 sections 7.24.3.
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When P is non-null realloc (P, 0) is worse, in that C23 says the
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behavior is undefined whereas POSIX.1-2024 (which extends C17) says
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that realloc (P, 0) when successful behaves like either (free (P),
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errno = EINVAL, NULL), or like (free (P), malloc (1)) returning non-null
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so long as you do not dereference the non-null pointer;
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and glibc does not conform to POSIX as it behaves like (free (P), NULL).
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There are similar issues with reallocarray.
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This behavior is sometimes unwelcome, as it entails extra checking
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to avoid confusing a zero-sized allocation with memory exhaustion,
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and to avoid undefined behavior in C23.
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This file provides malloc and realloc workalikes that consistently
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treat zero sizes as requests for zero-sized allocations instead of
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for null pointers. However, it does not provide workalikes for
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related functions like aligned_alloc, calloc, and reallocarray. */
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/* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE, _GL_ATTRIBUTE_ALLOC_SIZE,
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_GL_ATTRIBUTE_MALLOC. */
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#if !_GL_CONFIG_H_INCLUDED
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#error "Please include config.h first."
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#endif
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#include <stdlib.h>
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#if defined __CHERI_PURE_CAPABILITY__
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# include <cheri.h>
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#endif
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_GL_INLINE_HEADER_BEGIN
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#ifndef EEALLOC_INLINE
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# define EEALLOC_INLINE _GL_INLINE
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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#if MALLOC_0_IS_NONNULL
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# define eemalloc malloc
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#else
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EEALLOC_INLINE void *eemalloc (size_t n)
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_GL_ATTRIBUTE_MALLOC _GL_ATTRIBUTE_ALLOC_SIZE ((1))
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_GL_ATTRIBUTE_DEALLOC_FREE;
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EEALLOC_INLINE void *
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eemalloc (size_t n)
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{
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/* If n is zero, allocate a 1-byte block. */
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size_t nx = n;
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if (n == 0)
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nx = 1;
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void *ptr = malloc (nx);
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# if defined __CHERI_PURE_CAPABILITY__
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if (ptr != NULL)
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ptr = cheri_bounds_set (ptr, n);
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# endif
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return ptr;
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}
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#endif
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#if REALLOC_0_IS_NONNULL
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# define eerealloc realloc
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#else
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EEALLOC_INLINE void *eerealloc (void *p, size_t n)
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_GL_ATTRIBUTE_ALLOC_SIZE ((2));
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EEALLOC_INLINE void *
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eerealloc (void *p, size_t n)
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{
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/* Work around realloc glitch by treating a 0 size as if it were 1,
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to avoid undefined behavior in strict C23 platforms,
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and so that returning NULL is equivalent to failing. */
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void *ptr = realloc (p, n ? n : 1);
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# if defined __CHERI_PURE_CAPABILITY__
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if (ptr != NULL)
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ptr = cheri_bounds_set (ptr, n);
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# endif
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return ptr;
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}
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#endif
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/* Maybe we should also define variants
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eenmalloc (size_t n, size_t s) - behaves like eemalloc (n * s)
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eezalloc (size_t n) - like eemalloc followed by memset 0
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eecalloc (size_t n, size_t s) - like eemalloc (n * s) followed by memset 0
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eenrealloc (void *p, size_t n, size_t s) - like eerealloc (p, n * s)
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If this would be useful in your application. please speak up. */
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#ifdef __cplusplus
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}
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#endif
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_GL_INLINE_HEADER_END
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#endif /* _EEALLOC_H */
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