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Diffstat (limited to 'malloc/malloc-internal.h')
-rw-r--r-- | malloc/malloc-internal.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h new file mode 100644 index 0000000000..9cee0fb2d7 --- /dev/null +++ b/malloc/malloc-internal.h @@ -0,0 +1,97 @@ +/* Internal declarations for malloc, for use within libc. + Copyright (C) 2016-2018 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; see the file COPYING.LIB. If + not, see <http://www.gnu.org/licenses/>. */ + +#ifndef _MALLOC_INTERNAL_H +#define _MALLOC_INTERNAL_H + +#include <malloc-machine.h> +#include <malloc-sysdep.h> + +/* INTERNAL_SIZE_T is the word-size used for internal bookkeeping of + chunk sizes. + + The default version is the same as size_t. + + While not strictly necessary, it is best to define this as an + unsigned type, even if size_t is a signed type. This may avoid some + artificial size limitations on some systems. + + On a 64-bit machine, you may be able to reduce malloc overhead by + defining INTERNAL_SIZE_T to be a 32 bit `unsigned int' at the + expense of not being able to handle more than 2^32 of malloced + space. If this limitation is acceptable, you are encouraged to set + this unless you are on a platform requiring 16byte alignments. In + this case the alignment requirements turn out to negate any + potential advantages of decreasing size_t word size. + + Implementors: Beware of the possible combinations of: + - INTERNAL_SIZE_T might be signed or unsigned, might be 32 or 64 bits, + and might be the same width as int or as long + - size_t might have different width and signedness as INTERNAL_SIZE_T + - int and long might be 32 or 64 bits, and might be the same width + + To deal with this, most comparisons and difference computations + among INTERNAL_SIZE_Ts should cast them to unsigned long, being + aware of the fact that casting an unsigned int to a wider long does + not sign-extend. (This also makes checking for negative numbers + awkward.) Some of these casts result in harmless compiler warnings + on some systems. */ +#ifndef INTERNAL_SIZE_T +# define INTERNAL_SIZE_T size_t +#endif + +/* The corresponding word size. */ +#define SIZE_SZ (sizeof (INTERNAL_SIZE_T)) + +/* The corresponding bit mask value. */ +#define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1) + + +/* Called in the parent process before a fork. */ +void __malloc_fork_lock_parent (void) attribute_hidden; + +/* Called in the parent process after a fork. */ +void __malloc_fork_unlock_parent (void) attribute_hidden; + +/* Called in the child process after a fork. */ +void __malloc_fork_unlock_child (void) attribute_hidden; + +/* Called as part of the thread shutdown sequence. */ +void __malloc_arena_thread_freeres (void) attribute_hidden; + +/* Set *RESULT to LEFT * RIGHT. Return true if the multiplication + overflowed. */ +static inline bool +check_mul_overflow_size_t (size_t left, size_t right, size_t *result) +{ +#if __GNUC__ >= 5 + return __builtin_mul_overflow (left, right, result); +#else + /* size_t is unsigned so the behavior on overflow is defined. */ + *result = left * right; + size_t half_size_t = ((size_t) 1) << (8 * sizeof (size_t) / 2); + if (__glibc_unlikely ((left | right) >= half_size_t)) + { + if (__glibc_unlikely (right != 0 && *result / right != left)) + return true; + } + return false; +#endif +} + +#endif /* _MALLOC_INTERNAL_H */ |