1  /* Macros for declaring functions as non-returning.
       2  
       3     Copyright (C) 2017-2023 Free Software Foundation, Inc.
       4  
       5     This file is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU Lesser General Public License as
       7     published by the Free Software Foundation; either version 2.1 of the
       8     License, or (at your option) any later version.
       9  
      10     This file 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 Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser 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      || defined __clang__ \
      66      || (0x5110 <= __SUNPRO_C)
      67    /* For compatibility with _GL_NORETURN_FUNCPTR on clang, use
      68       __attribute__((__noreturn__)), not _Noreturn.  */
      69  # define _GL_NORETURN_FUNC __attribute__ ((__noreturn__))
      70  #elif 1200 <= _MSC_VER
      71    /* Use MSVC specific syntax.  */
      72  # define _GL_NORETURN_FUNC __declspec (noreturn)
      73  #elif defined __cplusplus
      74    /* Use ISO C++11 syntax when the compiler supports it.  */
      75  # if (__cplusplus >= 201103 && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
      76       || (_MSC_VER >= 1900)
      77  #  define _GL_NORETURN_FUNC [[noreturn]]
      78    /* clang++ supports the _Noreturn keyword, but g++ doesn't.  */
      79  # elif defined __clang__
      80  #  define _GL_NORETURN_FUNC _Noreturn
      81  # else
      82  #  define _GL_NORETURN_FUNC /* empty */
      83  # endif
      84  #else
      85    /* Use ISO C11 syntax when the compiler supports it.  */
      86  # if __STDC_VERSION__ >= 201112 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7)
      87  #  define _GL_NORETURN_FUNC _Noreturn
      88  # else
      89  #  define _GL_NORETURN_FUNC /* empty */
      90  # endif
      91  #endif
      92  
      93  /* Declares that a function is nonreturning.
      94     Use in types and declarations that involve function pointers:
      95       _GL_NORETURN_FUNCPTR void (*funcptr) (void);
      96   */
      97  #if (3 <= __GNUC__ || (__GNUC__ == 2 && 8 <= __GNUC_MINOR__)) \
      98      || defined __clang__ \
      99      || (0x5110 <= __SUNPRO_C)
     100  # define _GL_NORETURN_FUNCPTR __attribute__ ((__noreturn__))
     101  #else
     102  # define _GL_NORETURN_FUNCPTR /* empty */
     103  #endif
     104  
     105  /* Comments about the compiler dependent language features:
     106     - '_Noreturn'    - standardized by ISO C11, available in C only (not in C++),
     107                        and not applicable to pointers.
     108     - '[[noreturn]]' - standardized by ISO C++11, available in C++ only,
     109                        and not applicable to pointers.
     110     - '__attribute__((__noreturn__))' - available in GCC and clang only,
     111                                         both in C and C++.
     112     - '__declspec(noreturn)' - available in MSVC only,
     113                                both in C and C++, not applicable to pointers.
     114   */
     115  
     116  #endif /* _NORETURN_H */