Rethrow an exception like in C++?

[Ali Çehreli]

On 03/08/2013 11:26 AM, Rob T wrote:
> On Friday, 8 March 2013 at 17:40:38 UTC, Ali Çehreli wrote:
>> On 03/08/2013 12:39 AM, Rob T wrote:
>> > In C++ you can do this
>> >
>> > std::exception Trace()
>> > {
>> > try
>> > {
>> > // key item missing from D
>> > throw; // <= rethrow last exception
>>
>> This idiom is know as a Lippincott Function.
>>
>> Ali
>
> I'm having trouble finding references on Lippincott Function, so if you
> have any more information, please let me know. Thanks.
>
> --rt

I heard about this idiom for the first time in Jon Kalb's talk. The name 
appears in his slides:

   http://exceptionsafecode.com/

Very smart way of writing a single function that catches many different 
types of exceptions; does special things about them, like producing 
special error codes, and then returns those codes to the C world.

I am familiar with your use case: When a C layer calls C++, the 
exceptions must be caught and converted to error codes. This is how we 
do it:

#define BEGIN_C_INTERFACE try {

#define END_C_INTERFACE                                     \
} catch (const SomeType & e) {                              \
   // ... special code for SomeType                          \
} catch (const SomeOtherType & e) {                         \
   // ... special code for SomeOtherType                     \
                                                             \
// ... etc.                                                 \
                                                             \
} catch( ... ) {                                            \
     log("Unhandled exception");                             \
     return some_generic_error_code;                         \
}

Then our C++ functions that are called from C are like this:

extern "C"
int my_api_func()
{
     BEGIN_C_INTERFACE

     // ... the actual body of the function

     END_C_INTERFACE
}

Lippincott functions avoid macros and make it more explicit that the 
entire body is inside a try block.

Ali