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Re: Crash occurs when catching std::exception in Objective-C++ code comp

From: Lobron, David
Subject: Re: Crash occurs when catching std::exception in Objective-C++ code compiled with clang on Linux and using libobjc2
Date: Tue, 21 Nov 2017 16:13:39 +0000

> This looks like it’s trying to all a version with C++ name mangling.  Try 
> sticking an extern “C” { } around the #includes.

Thanks, David.  That extern statement did not fix the compilation problem, but 
I was able to simplify things by reverting to my original test program that 
simply throws a C++ std::exception in code compiled with a .mm suffix.  That 
program now builds and runs correctly, whereas previously, it crashed.  So I 
think the changes we made do fix the problem.

Unfortunately, my main program is still crashing with a NULL exception.  I'm 
now wondering if there's something wrong with my build command, or maybe with 
the runtime flags I'm passing to my main program.

I ran nm on the test program to see what exception personality it uses:

$ nm -C CXXException_mm|grep -i except
                 U __cxa_allocate_exception@@CXXABI_1.3
0000000000400ea4 r GCC_except_table0
                 U std::exception::~exception()@@GLIBCXX_3.4
00000000006020d0 V typeinfo for std::exception@@GLIBCXX_3.4
00000000006020a0 V vtable for std::exception@@GLIBCXX_3.4

I checked for those strings in my main program, and the result was similar, 
although not identical:

$ nm -C obj/mapmaker|grep __cxa_allocate_exception
                 U __cxa_allocate_exception@@CXXABI_1.3
(ALSI8)dlobron@bos-lps80:~/build/clangport/akamai/mapmaker$ nm -C 
obj/mapmaker|grep std::exception   
                 U std::exception::~exception()@@GLIBCXX_3.4
                 U typeinfo for std::exception@@GLIBCXX_3.4

The only difference here is that the non-working main program doesn't have 
"vtable for std::exception".  Could that be the source of the problem?  Or 
could this be a runtime or compile-time difference in my code?


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