| /* 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; |
| |
| /* 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 */ |