I am trying to catch a divide-by-zero error with the following code:

#include <iostream>
using namespace std;

int main() {
   try {
       int a = 0;
       int x = 5 / a;
   }
   catch (exception e)
   {
       cout << e.what() << endl;
   }
   catch (...)
   {
       cout << "caught ..." << endl;
   }

}

For some reason, neither of my catch blocks gets executed. Anyone know how to catch the exception?

Thank you.

mike74 said:
For some reason, neither of my catch blocks gets executed. Anyone know how to catch the exception?

divide-by zero is not a “managed” exception. You can still catch it, but it depends on the OS you are using. I'm just assuming you use windows.

There, you would need to use structured-exception handling (which is for system-level exceptions):

__try
{
       int a = 0;
       int x = 5 / a;
}
__except ((_exception_code() == _STATUS_FLOAT_DIVIDE_BY_ZERO || _exception_code() == _STATUS_INTEGER_DIVIDE_BY_ZERO) ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
{
       cout << "caught ..." << endl;
}

SEH is much more restricted and low-level than standard exceptions, so you shouldn't use it willy-nilly (and should actually think of another way of handling those errors for the general case). You should probably just check if “a” is 0 and throw your own exception, in the general case.

If you do use SEH, there are two restrictions that you will encounter very early:

1. SEH and managed exceptions can't be matched. Meaning, you cannot have both __try and try in the same function. You can solve this by adding a wrapper-function for the other type of exception-handler.
2. Locals with destructors (pretty much anything that is non POD) in a function with an SEH-handler are limited. IIRC, you cannot declare a destructable-local before and SEH-handler; or perhaps not at all. You can again solve this by moving the SEH-handler in a wrapper-function.

As you see, most normal usages of SEH are limited. If you haVe to add a wrapper to handle exceptions, you might as well just handle them yourself. SEH is more used for last-ditch error handling (for like a crash-reporter), or where handling all exceptions manually would be tedious (I haVe an own compiler that can execute c++-functions at compile-time; I use SEH to catch any error like div-by-zero during this evaluation gracefully and defer to a compiler-error, without having to sprinkle those functions with manual throws.

@Juliean I'm on Windows, but it's just a Console app. Can you tell me which headers I need to include?

Thanks.

https://learn.microsoft.com/en-us/cpp/cpp/structured-exception-handling-c-cpp?view=msvc-170​

See the example on this page for how to set this up, and also a general explanation for how this works. I'm not entirely sure this works on a console-app, but it should (as long as you have access to the windows-headers).