On Thursday, 12 November 2015 at 06:50:31 UTC, Walter Bright
wrote:
In order to interoperate with modern C++, it has been
abundantly clear for some time that D needs some support for
C++ exception handling:
1. Have D finally blocks executed in D code that sits between a
C++ try and catch
2. Have C++ finally blocks executed in C++ code that sits
between a D try and catch
3. Be able to catch in D code an std::exception* or a C++ class
derived from that.
4. Throw an std::exception* from D code.
That's the minimum credible support, and is likely all D will
actually need.
I also started working on C++ exception handling for LDC/Calypso,
I almost caught my first std::exception yesterday! (it went into
the right catch and the IR looks right but _cxa_begin_catch()
seems to return null instead of the exception object for some
reason)
Clang and Calypso made the std::type_info stuff a breeze, getting
the type_info value for any C++ type was one line of code.
I'll push the changes as is into a branch tonight, it's about
~400 lines.
The tricky part with the personality function will likely be
recognizing std::exception* exceptions. I wonder if forwarding
the call to __gxx_personality_v0 will work.
From what I gathered even if you manage to make the format of the
LSDA tables compatible with __gxx_personality_v0, one blocker is
that it still expects std::type_info pointers in the action table
so will choke if it encounters D's TypeInfo_Class in there.
To check if a type_info from a catch clause handles the thrown
exception it calls the virtual method type_info::__do_catch
(which is what Calypso does too) so can't work with D classes.
