Is there anything that would prevent D from catching C++ exceptions?

It would be nice to be able to leverage C++ libraries, but if you can't catch C++ exceptions, I'm not sure how realistic that is.

That doesn't mean that catch() in D has to be the catcher.

If there was some way to indicate that a function call was into a C++ library, and perhaps some way to auto-generate, at the call point, the boilerplate that does the "catch this C++ exception and re-throw it as a D exception" translation, that would be awesome.

Possible?

this might be relevant: see code that Swig generates when writing C++ wrappers :

eg:
----
// Support for throwing D exceptions from C/C++.
typedef enum {
  SWIG_DException = 0,
  SWIG_DIllegalArgumentException,
  SWIG_DIllegalElementException,
  SWIG_DIOException,
  SWIG_DNoSuchElementException,
} SWIG_DExceptionCodes;

typedef void (* SWIG_DExceptionCallback_t)(const char *);
----

On Fri, Mar 29, 2013 at 10:06 PM, J <noname@notavailable.notavailabe.com> wrote:
> Is there anything that would prevent D from catching C++ exceptions?
>
> It would be nice to be able to leverage C++ libraries, but if you can't catch C++ exceptions, I'm not sure how realistic that is.
>
> That doesn't mean that catch() in D has to be the catcher.
>
> If there was some way to indicate that a function call was into a C++ library, and perhaps some way to auto-generate, at the call point, the boilerplate that does the "catch this C++ exception and re-throw it as a D exception" translation, that would be awesome.
>
> Possible?

On 2013-03-30 05:06:31 +0000, "J" <noname@notavailable.notavailabe.com> said:

> Is there anything that would prevent D from catching C++ exceptions?
> 
> It would be nice to be able to leverage C++ libraries, but if you can't catch C++ exceptions, I'm not sure how realistic that is.
> 
> That doesn't mean that catch() in D has to be the catcher.
> 
> If there was some way to indicate that a function call was into a C++ library, and perhaps some way to auto-generate, at the call point, the boilerplate that does the "catch this C++ exception and re-throw it as a D exception" translation, that would be awesome.
> 
> Possible?

In my D/Objective-C hack I made a few years ago, I made it work for Objective-C exceptions [1]. So it's certainly doable.

[1]: http://michelf.ca/projects/d-objc/syntax/#exceptions

It would be more tricky though because C++ exceptions are thrown by-value. And some things will have to work differently to accommodate each platform's ABI. And you'll likely get a performance penalty in normal code for settings the handler frames.

But it can be done.


-- 
Michel Fortin
michel.fortin@michelf.ca
http://michelf.ca/

There was a discussion about Exceptions in D.learn that may be relevant.

http://forum.dlang.org/thread/yqzjldpknloyxwlbuxlk@forum.dlang.org

If you look though the discussion towards the end you'll see mention of "Lippincott functions", and from there a C++ exception handler example is shown where you can catch any exception in C++. With an exception handler it becomes practical to convert any C++ exception into something that D will understand through a wrapper function that is exported to D. You won't of course be catching the C++ exceptions directly inside D (and you will never want to anyway), but you should be able to convert them into corresponding D exceptions and catch them from inside your D code.

If you have any success with this, please share your experience.

--rt