FreeBSD/Linux Kernel Cross Reference
sys/compat/linuxkpi/common/include/linux/overflow.h

     /*-
      * Copyright (c) 2020 The FreeBSD Foundation
      *
      * This software was developed by Emmanuel Vadot under sponsorship
      * from the FreeBSD Foundation.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    
    #ifndef __LINUXKPI_LINUX_OVERFLOW_H__
    #define __LINUXKPI_LINUX_OVERFLOW_H__
    
    #include <sys/stdint.h>
    #include <sys/types.h>
    
    #define check_add_overflow(a, b, c)             \
            __builtin_add_overflow(a, b, c)
    
    #define check_mul_overflow(a, b, c)     \
            __builtin_mul_overflow(a, b, c)
    
    static inline size_t
    array_size(size_t x, size_t y)
    {
            size_t retval;
    
            if (__builtin_mul_overflow(x, y, &retval))
                    retval = SIZE_MAX;
            return (retval);
    }
    
    #endif  /* __LINUXKPI_LINUX_OVERFLOW_H__ */

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