Is there a way to know if exceptions have been disabled? - c++

Question

Is there a way to know if exceptions have been disabled in C++?
I'm developing an application that uses exceptions and I want to avoid having the user compile the application with exceptions disabled, like a warning that you need exceptions.

Answer 1

The standard certainly does not entertain such a functionality.
Assuming you are using a modern and competent compiler to compile code that contains a throw, then the compiler will error. But you can of course compile one part of the code WITH exceptions, and another without, in which case you still get exceptions thrown, but no way of catching them (since there is no catch either). So the program will probably terminate on first exception being thrown.
If you supply headers, you could just add a dummy function in an unnamed namespace:
namespace {
inline void dummy_dummy_my_thing_to_check_exceptions()
{
throw 123;
}
}
and never even call that function, it will still fail to compile.
I doubt that any compiler that lets you turn off exceptions will accept code that does this - I have tried with g++ 4.8.2, g++ 4.6.3, clang++ 3.6.0 (as of three weeks ago) and clang++ 2.9. All give an error for the above function inside a headerfile. If I remove -fno-exceptions, the code compiles and runs (with a terminate becuase the code does throw 1 in a function.
Total code:
x.h:
extern int func();
namespace {
inline void dummy_dummy_my_thing_to_check_exceptions()
{
throw 123;
}
}
x.cpp:
int func()
{
throw 1;
}
except.cpp:
#include "x.h"
int main()
{
func();
}
Compiles with:
g++ -c except.cpp && g++ except.o x.cpp
or
clang++ -c except.cpp && clang++ except.o,
but won't compile with:
g++ -c except.cpp -fno-exceptions && g++ except.o x.cpp
or
clang++ -c except.cpp -fno-exceptions && clang++ except.o.