On 21 February 2018 at 14:15, Jeffrey Walton wrote:
> Hi Everyone,
>
> I'm trying to determine when I can use std::uncaught_exceptions().
>
> $ cat test.cxx
> #include <iostream>
>
> #ifndef __has_feature
> # define __has_feature(x) 0
> #endif
>
> #if _MSC_VER >= 1900
> # define MY_EXCEPTIONS 1
> #elif __has_feature(cxx_exceptions)
__has_feature is a Clang extension, GCC doesn't support it, so this is
always false.
> # define MY_EXCEPTIONS 1
> #endif
>
> #ifdef MY_EXCEPTIONS
> # include <exception>
> #endif
>
> int main(int argc, char* argv[])
> {
> #ifdef MY_EXCEPTIONS
> std::cout << std::uncaught_exceptions() << std::endl;
You're assuming that if Clang's cxx_exceptions feature is present then
so is the new C++17 function, which is wrong.
The recommended way to test for exceptions being enabled is to test
#if __cpp_exceptions
(that works on Clang and GCC, but not MSVC because they don't support
WG21 SD-6 feature-test macros).
The recommended way to test for std::uncaught_exceptions is #if
__cpp_lib_uncaught_exceptions >= 201411
(that works with libstdc++ but not MSVC or libc++ because they don't
support WG21 SD-6 feature-test macros for the standard library).
SD-6 can be found at
https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
