How do I detect if my code is being compiled with -fno-exceptions?

Question

I'm writing a C++ library and I would like to make my API throw exceptions for invalid parameters, but rely on asserts instead when the code is compiled with -fno-exceptions.

Is there a way to detect at compile-time if I'm allowed to use exception handling? Note that I'm writing a header-only library, so I don't have a configure phase and I don't have access to the build system to simply define a macro on the command line (and I don't want to add burden to the user).

Since the Standard doesn't have any concept of "-fno-exceptions", of course the solution could be compiler-dependent. In this case I'm interested in solutions that work with both g++ and clang++, other compilers are not important for this project.

Thank you very much

Answer 1

GCC and Clang define the __EXCEPTIONS macro when exceptions are enabled, and do not define it when exceptions are disabled via -fno-exceptions.

Example:

#include <cstdio>
int main() {
#ifdef __EXCEPTIONS
    puts("Exceptions are enabled");
#else
    puts("Exceptions are disabled");
#endif
}