C++ catch enum value as exception

Question

I am trying to use an external C++ library which have defined its exceptions as:

enum MY_ERRORS { ERR_NONE = 0, ERR_T1, ERR_T2, };

Then in the code exceptions are thrown like this:

if(...) { throw ERR_T1;

Being new to programming in C++, I would do something like:

try { call_to_external_library(); } catch(??? err) { printf("An error occurred: %s\n", err); } catch(...) { printf("An unexpected exception occurred.\n"); }

How do I determine what was thrown?

err should be MY_ERRORS or const MY_ERRORS& or something like this (doesn't matter much for enums). In the catch( ... ) you cannot get the type of the caught exception — Kiril Kirov
– Kiril Kirov, Commented Jan 6, 2014 at 13:36

utnapistim · Accepted Answer · 2014-01-06 13:36:40Z

You will need to write your code to handle the type of enumeration in the catch block:

try { call_to_external_library(); } catch(MY_ERRORS err) { // <------------------------ HERE printf("An error occurred: %s\n", err); } catch(...) { printf("An unexpected exception occurred.\n"); }

You might consider wrapping the enum in a type that derives from std::exception so that it can be caught like a normal exception. Not necessary, but it can be nice to have a more uniform way to catch things.

Olaf Dietsche · Accepted Answer · 2014-01-06 13:36:44Z

You must catch the type MY_ERRORS and then compare against the possible values

try { call_to_external_library(); } catch(MY_ERRORS err) { printf("An error occurred: %s\n", err); } catch(...) { printf("An unexpected exception occurred.\n"); }

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