[cfe-dev] Latest clang from source breaks clang on Windows targeting gcc linking
Edward Diener
eldlistmailingz at tropicsoft.com
Sun Aug 9 09:33:15 PDT 2015
On 8/8/2015 9:03 PM, Yaron Keren wrote:
> See r244407 for a fuller patch with test case. It may also solve the
> other issues.
> If not, the best way to diagnose such problem is to run clang++ and g++
> with -v argument and the same pther arguments of the case, comparing
> both compiler outputs to see what's different.
> With this input we could patch the mingw toolchain.
I removed the patch you pointed me to earlier in this thread and
downloaded and built the latest llvm/clang. Now when I compile/link with
clang I get neither the "undefined reference to `__chkstk_ms'" error or
the "undefined reference to `_Unwind_Resume'" error. Those errors may
have been caused by my building clang with a different version of gcc
than the one I use for RTL when I run clang, or may have been fixed by
the latest clang changes in source, but whatever the reason those errors
no longer occur. Hooray !
This leads me to the general question: if I build llvm/clang with a
particular version of mingw(-64)/gcc on Windows is it an error if I use
another version of mingw(-64)/gcc on Windows RTL when I compile/link
with clang ?
Onward to my original problem:
If I compile/link by exporting a class as a whole and then import the
class as a whole, when linking with that DLL, everything works fine.
If I compile/link by exporting individual member functions of a visible
class, when I try to import those same individual member functions when
linking with that DLL I still get an error of the form:
"undefined reference to `typeinfo for ex_xml_exception'"
where ex_xml_exception is the class I am using as a whole in throwing a
C++ exception. So it appears that exporting/importing individual member
functions of a class is still not exporting/importing the typeinfo
information of the class as a whole.
Can someone look into this again and see if it can be fixed in clang on
Windows targeting gcc ?
The main reason I am trying to get clang on Windows working this way is
that I am trying to get the latest build of Boost serialization working
with the latest clang, and the latest design of Boost serialization ( I
am not the designer ) is to export/import only the individual member of
a class rather than the class as a whole.
>
>
> 2015-08-08 22:37 GMT+03:00 Edward Diener <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz-5p0dqD/c5LGWd6l5hS35sQ at public.gmane.org>>:
>
> 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-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org
> <mailto:c5LGWd6l5hS35sQ-XMD5yJDbdMSQIYZ4X/+iSw at public.gmane.orgrg>
> <mailto:eldlistmailingz-5p0dqD
> <mailto:eldlistmailingz-5p0dqD>/c5LGWd6l5hS35sQ-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org
> <mailto:c5LGWd6l5hS35sQ-XMD5yJDbdMReXY1tMh2IBg 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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