[Mono-devel-list] RAPGO Proposal
jonpryor at vt.edu
Tue Nov 30 07:48:15 EST 2004
> The other thing is that you can't catch C++ exceptions thrown in P/I
> code by using a C-only approach.. Yes, I know that this is not supported
> by mono, but somehow I thought adding this feature would be interesting.
> Currently mono just gets terminated by the C runtime if a C++ exception
> is thrown in native P/I code because no exception handler can be found..
In theory, you're possibly correct. In practice, you're not. :-)
The problem is that on most platforms the C++ ABI isn't standardized.
Consequently, you can't link object code generated by different C++
compilers together. Consequently, Mono could only handle C++ exceptions
generated by the same C++ compiler used to compile Mono.
On Linux, this isn't a particularly major issue (except when the C++ ABI
changes, such as in GCC 3.0, 3.1, 3.2...). On other platforms which
have their own compiler in addition to GCC (SunOS, AIX, HP/UX, Windows,
all of which have their own vendor-supported C++ compilers), it is
highly unlikely that exceptions could be passed from unmanaged to
Consider a Sun-generated C++ code which throws an exception being
handled by a GCC-compiled Mono runtime. Mono would still die. Ditto
for Windows SEH as used by MSVC and a GCC-compiled Mono runtime.
The only platforms where C++ and Mono exceptions could possibly work
portably is on platforms where the C++ ABI is standardized. The only
such platform I'm aware of is IA64 (Itanic, er, Itanium), and Mono
doesn't have a JIT for that platform AFAIK.
Furthermore, if the platform *does* have a C++ ABI standard, then Mono
could just re-use the C++ exception structures, allowing C++ exceptions
to be properly handled by the Mono runtime. A C++ compiler wouldn't be
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