1 /* Macros for declaring functions as non-returning. 2 3 Copyright (C) 2017-2020 Free Software Foundation, Inc. 4 5 This program is free software: you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 17 18 /* Written by Paul Eggert and Bruno Haible. */ 19 20 #ifndef _NORETURN_H 21 #define _NORETURN_H 1 22 23 /* A "non-returning" function is a function which cannot return normally. 24 It can transfer control only through longjmp(), throw (in C++), or similar 25 mechanisms. 26 27 This file defines two macros _GL_NORETURN_FUNC and _GL_NORETURN_FUNCPTR, 28 that declare a function to be non-returning. 29 _GL_NORETURN_FUNC is for use in function declarations and function 30 definitions. 31 _GL_NORETURN_FUNCPTR is for use on function pointers. 32 33 Comparison of this file with <stdnoreturn.h>: 34 <stdnoreturn.h> defines a macro (or keyword) _Noreturn that declares 35 a function to be non-returning. _Noreturn is only for use in function 36 declarations and function definitions. 37 Therefore, if the non-returning functions you have to declare are unlikely 38 to be accessed through function pointers, and if the efficiency with C++ 39 compilers other than g++, clang, MSVC++ is not an issue to you, you can use 40 module 'stdnoreturn' instead of this one, and _Noreturn instead of 41 _GL_NORETURN_FUNC. 42 */ 43 44 /* Declares that a function is nonreturning. 45 Use in C only code: 46 _GL_NORETURN_FUNC extern void func (void); 47 extern _GL_NORETURN_FUNC void func (void); 48 extern void _GL_NORETURN_FUNC func (void); 49 Use in C++ only code for a function with C linkage: 50 extern "C" { _GL_NORETURN_FUNC void func (void); } 51 Use in C++ only code for a function with C++ linkage: 52 _GL_NORETURN_FUNC extern void func (void); 53 Use in C & C++ code for a function with C linkage: 54 #ifdef __cplusplus 55 extern "C" { 56 #endif 57 _GL_NORETURN_FUNC void func (void); 58 #ifdef __cplusplus 59 } 60 #endif 61 Use in C & C++ code for a function with current language linkage: 62 _GL_NORETURN_FUNC extern void func (void); 63 */ 64 #if (3 <= __GNUC__ || (__GNUC__ == 2 && 8 <= __GNUC_MINOR__)) \ 65 || (0x5110 <= __SUNPRO_C) 66 /* For compatibility with _GL_NORETURN_FUNCPTR on clang, use 67 __attribute__((__noreturn__)), not _Noreturn. */ 68 # define _GL_NORETURN_FUNC __attribute__ ((__noreturn__)) 69 #elif 1200 <= _MSC_VER 70 /* Use MSVC specific syntax. */ 71 # define _GL_NORETURN_FUNC __declspec (noreturn) 72 #elif defined __cplusplus 73 /* Use ISO C++11 syntax when the compiler supports it. */ 74 # if (__cplusplus >= 201103 && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \ 75 || (_MSC_VER >= 1900) 76 # define _GL_NORETURN_FUNC [[noreturn]] 77 /* clang++ supports the _Noreturn keyword, but g++ doesn't. */ 78 # elif defined __clang__ 79 # define _GL_NORETURN_FUNC _Noreturn 80 # else 81 # define _GL_NORETURN_FUNC /* empty */ 82 # endif 83 #else 84 /* Use ISO C11 syntax when the compiler supports it. */ 85 # if __STDC_VERSION__ >= 201112 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7) 86 # define _GL_NORETURN_FUNC _Noreturn 87 # else 88 # define _GL_NORETURN_FUNC /* empty */ 89 # endif 90 #endif 91 92 /* Declares that a function is nonreturning. 93 Use in types and declarations that involve function pointers: 94 _GL_NORETURN_FUNCPTR void (*funcptr) (void); 95 */ 96 #if (3 <= __GNUC__ || (__GNUC__ == 2 && 8 <= __GNUC_MINOR__)) \ 97 || (0x5110 <= __SUNPRO_C) 98 # define _GL_NORETURN_FUNCPTR __attribute__ ((__noreturn__)) 99 #else 100 # define _GL_NORETURN_FUNCPTR /* empty */ 101 #endif 102 103 /* Comments about the compiler dependent language features: 104 - '_Noreturn' - standardized by ISO C11, available in C only (not in C++), 105 and not applicable to pointers. 106 - '[[noreturn]]' - standardized by ISO C++11, available in C++ only, 107 and not applicable to pointers. 108 - '__attribute__((__noreturn__))' - available in GCC and clang only, 109 both in C and C++. 110 - '__declspec(noreturn)' - available in MSVC only, 111 both in C and C++, not applicable to pointers. 112 */ 113 114 #endif /* _NORETURN_H */ 115