<html lang="en"> <head> <title>Integer Overflow Builtins - Using the GNU Compiler Collection (GCC)</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Using the GNU Compiler Collection (GCC)"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> <link rel="prev" href="_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins" title="__atomic Builtins"> <link rel="next" href="x86-specific-memory-model-extensions-for-transactional-memory.html#x86-specific-memory-model-extensions-for-transactional-memory" title="x86 specific memory model extensions for transactional memory"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being ``Funding Free Software'', the Front-Cover Texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the section entitled ``GNU Free Documentation License''. (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.--> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Integer-Overflow-Builtins"></a> <p> Next: <a rel="next" accesskey="n" href="x86-specific-memory-model-extensions-for-transactional-memory.html#x86-specific-memory-model-extensions-for-transactional-memory">x86 specific memory model extensions for transactional memory</a>, Previous: <a rel="previous" accesskey="p" href="_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins">__atomic Builtins</a>, Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> <hr> </div> <h3 class="section">6.52 Built-in Functions to Perform Arithmetic with Overflow Checking</h3> <p>The following built-in functions allow performing simple arithmetic operations together with checking whether the operations overflowed. <div class="defun"> — Built-in Function: bool <b>__builtin_add_overflow</b> (<var>type1 a, type2 b, type3 *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fadd_005foverflow-3562"></a></var><br> — Built-in Function: bool <b>__builtin_sadd_overflow</b> (<var>int a, int b, int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsadd_005foverflow-3563"></a></var><br> — Built-in Function: bool <b>__builtin_saddl_overflow</b> (<var>long int a, long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsaddl_005foverflow-3564"></a></var><br> — Built-in Function: bool <b>__builtin_saddll_overflow</b> (<var>long long int a, long long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsaddll_005foverflow-3565"></a></var><br> — Built-in Function: bool <b>__builtin_uadd_overflow</b> (<var>unsigned int a, unsigned int b, unsigned int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fuadd_005foverflow-3566"></a></var><br> — Built-in Function: bool <b>__builtin_uaddl_overflow</b> (<var>unsigned long int a, unsigned long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fuaddl_005foverflow-3567"></a></var><br> — Built-in Function: bool <b>__builtin_uaddll_overflow</b> (<var>unsigned long long int a, unsigned long long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fuaddll_005foverflow-3568"></a></var><br> <blockquote> <p>These built-in functions promote the first two operands into infinite precision signed type and perform addition on those promoted operands. The result is then cast to the type the third pointer argument points to and stored there. If the stored result is equal to the infinite precision result, the built-in functions return false, otherwise they return true. As the addition is performed in infinite signed precision, these built-in functions have fully defined behavior for all argument values. <p>The first built-in function allows arbitrary integral types for operands and the result type must be pointer to some integer type, the rest of the built-in functions have explicit integer types. <p>The compiler will attempt to use hardware instructions to implement these built-in functions where possible, like conditional jump on overflow after addition, conditional jump on carry etc. </blockquote></div> <div class="defun"> — Built-in Function: bool <b>__builtin_sub_overflow</b> (<var>type1 a, type2 b, type3 *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsub_005foverflow-3569"></a></var><br> — Built-in Function: bool <b>__builtin_ssub_overflow</b> (<var>int a, int b, int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fssub_005foverflow-3570"></a></var><br> — Built-in Function: bool <b>__builtin_ssubl_overflow</b> (<var>long int a, long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fssubl_005foverflow-3571"></a></var><br> — Built-in Function: bool <b>__builtin_ssubll_overflow</b> (<var>long long int a, long long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fssubll_005foverflow-3572"></a></var><br> — Built-in Function: bool <b>__builtin_usub_overflow</b> (<var>unsigned int a, unsigned int b, unsigned int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fusub_005foverflow-3573"></a></var><br> — Built-in Function: bool <b>__builtin_usubl_overflow</b> (<var>unsigned long int a, unsigned long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fusubl_005foverflow-3574"></a></var><br> — Built-in Function: bool <b>__builtin_usubll_overflow</b> (<var>unsigned long long int a, unsigned long long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fusubll_005foverflow-3575"></a></var><br> <blockquote> <p>These built-in functions are similar to the add overflow checking built-in functions above, except they perform subtraction, subtract the second argument from the first one, instead of addition. </blockquote></div> <div class="defun"> — Built-in Function: bool <b>__builtin_mul_overflow</b> (<var>type1 a, type2 b, type3 *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fmul_005foverflow-3576"></a></var><br> — Built-in Function: bool <b>__builtin_smul_overflow</b> (<var>int a, int b, int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsmul_005foverflow-3577"></a></var><br> — Built-in Function: bool <b>__builtin_smull_overflow</b> (<var>long int a, long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsmull_005foverflow-3578"></a></var><br> — Built-in Function: bool <b>__builtin_smulll_overflow</b> (<var>long long int a, long long int b, long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsmulll_005foverflow-3579"></a></var><br> — Built-in Function: bool <b>__builtin_umul_overflow</b> (<var>unsigned int a, unsigned int b, unsigned int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fumul_005foverflow-3580"></a></var><br> — Built-in Function: bool <b>__builtin_umull_overflow</b> (<var>unsigned long int a, unsigned long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fumull_005foverflow-3581"></a></var><br> — Built-in Function: bool <b>__builtin_umulll_overflow</b> (<var>unsigned long long int a, unsigned long long int b, unsigned long int *res</var>)<var><a name="index-g_t_005f_005fbuiltin_005fumulll_005foverflow-3582"></a></var><br> <blockquote> <p>These built-in functions are similar to the add overflow checking built-in functions above, except they perform multiplication, instead of addition. </blockquote></div> </body></html>