[cfe-dev] Latest clang from source breaks clang on Windows targeting gcc linking

[Edward Diener]

On 8/8/2015 1:59 PM, Yaron Keren wrote:
> I'm looking into this, see https://llvm.org/bugs/show_bug.cgi?id=24395
> The solution is somewhat more compilcated but you can use the patch
> there for now.

The patch solved the general problem I illustrated below. Thanks !

But for the example in my other posts, where an exception was being 
thrown from a module using as a type a class that is in another DLL that 
is being exported/imported, the attempt to link to that DLL now fails with:

ex_exception.obj: In function `ex_exception':
ex_exception.cpp:42: undefined reference to `_Unwind_Resume'
ex_xml_exception.obj: In function `ex_xml_exception':
ex_xml_exception.cpp:32: undefined reference to `_Unwind_Resume'
ex_xml_exception.cpp:39: undefined reference to `_Unwind_Resume'
ex_xml_exception.cpp:42: undefined reference to `_Unwind_Resume'
clang++.exe: error: linker command failed with exit code 1 (use -v to 
see invocation)

These error messages are exactly the same whether or not I attempt to 
export/import the individual member functions of a visible class or 
whether I attempt to export/import the class as a whole. At least the 
previous error messages which occurred in the above situation have 
disappeared <g>.

If you need for me to repeat the ex_exception, ex_xml_exception, and 
throw_exception_ex source, with their command lines, in this post I will 
be glad to do it.

Searching the web for "undefined reference to `_Unwind_Resume'" yields 
various possibilities but none are definitive for this case AFAICS.

>
> 2015-08-08 20:20 GMT+03:00 Edward Diener
> <eldlistmailingz-5p0dqD/c5LGWd6l5hS35sQ at public.gmane.org
> <mailto:eldlistmailingz-5p0dqD/c5LGWd6l5hS35sQ at public.gmane.org>>:
>
>     Some change in the latest source has completely broken linking for
>     clang on Windows targeting gcc.
>
>     // ex_aclass.hpp
>
>     #ifndef EX_ACLASS_HPP
>     #define EX_ACLASS_HPP
>     #if defined(BLD_EX_EXAMPLE)
>              #define EX_DECL __attribute__((__dllexport__))
>     #else
>              #define EX_DECL __attribute__((__dllimport__))
>     #endif
>     class EX_DECL ex_aclass
>     {
>     public:
>          int a_function(long);
>     };
>     #endif // EX_ACLASS_HPP
>
>     // ex_aclass.cpp
>
>     #define BLD_EX_EXAMPLE
>     #include "ex_aclass.hpp"
>     int ex_aclass::a_function(long amt)
>              {
>              return(amt > 1000000 ? 10 : 20);
>              }
>
>     // Compile ex_aclass.cpp
>
>     clang++.exe -c -x c++ -D__MINGW_FORCE_SYS_INTRINS -O0 -g -fno-inline
>     -Wall -g -march=i686 -m32 -o "ex_aclass.obj" "ex_aclass.cpp"
>
>     // Link into ex_ac.dll
>
>     clang++.exe" -o "ex_ac.dll" -Wl,-soname -Wl,ex_ac.dll -shared
>     -Wl,--start-group "ex_aclass.obj" -Wl,-Bstatic -Wl,-Bdynamic
>     -Wl,--end-group -g -march=i686 -m32
>
>     libmingw32.a(lib32_libmingw32_a-pseudo-reloc.o):pseudo-reloc.c:(.text+0x1d6):
>     undefined reference to `__chkstk_ms'
>     clang++.exe: error: linker command failed with exit code 1 (use -v
>     to see invocation)
>
>     Nor does it matter what source file is used in general, whenever the
>     link is done for anything the "undefined reference to `__chkstk_ms'"
>     occurs.
>
>     Can some one of the clang developers please look at this ?
>
>     I am using clang on Windows with the 32-bit version of
>     mingw-64/gcc-5.1 as i686-5.1.0-posix-dwarf-rt_v4-rev0.
>
>     I realize the current problems for clang on Windows targeting gcc
>     may have occurred trying to fix a more specific problem I reported
>     in two other threads about linkage failure using dllexport and
>     dllimport attributes on Windows, but going from a situation where a
>     specific problem broke the linking to all situations are broken when
>     attempting to link is not good.
>
>     I tried looking at the clang unit tests and how they can be run on
>     Windows but found very little information about both. I wouldn't
>     mind contributing some basic unit tests, even though I am not a
>     clang developer, just to make sure that clang on Windows targeting
>     gcc will work when compiling/linking dlls and using those dlls from
>     another module, if I could understand what to do. That way such a
>     snafu as this latest breakage would not occur so easily as whatever
>     broke in the change should have been caught by some unit tests.
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>
>
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