[Ping] Port of VTV for Cygwin and MinGW

[Patrick Wollgast]

Ping for https://gcc.gnu.org/ml/gcc-patches/2014-08/msg02559.html

Also added Caroline Tice, as libvtv maintainer, to cc and attached
virtual_func_test_min_UAF.cpp, which I forgot in the original mail.

Patrick

On 28.08.2014 13:03, Patrick Wollgast wrote:
> This patch contains a port of VTV -fvtable-verify=std for Cygwin and MinGW.
> 
> Since weak symbols on Windows and Linux are implemented differently, and
> VTV should have the possibility to be switched on and off, the structure
> of the feature had to be modified.
> On Linux libstdc++ contains the weak stub functions of VTV. For Cygwin
> and MinGW they have been removed, due to the difference of weak symbols.
> On Linux and on Windows libstdc++ itself gets build with
> -fvtable-verify=std. Since libvtv gets build after libstdc++, and
> libstdc++ doesn't contain the stub functions any more, 'undefined
> reference' errors are thrown during linking of libstdc++. To prevent
> these errors during the linking process a libvtv-0.dll gets build from
> the stub functions before libstdc++-6.dll is linked.
> At the end of the build process two VTV dlls have been build. One is
> called libvtv-0.dll, containing the real functions, the other is called
> libvtv_stubs-0.dll, containing the stub functions. Depending on whether
> libvtv-0.dll is first found in the dll search path or
> libvtv_stubs-0.dll, renamed to libvtv-0.dll, the real functions or the
> stub functions are used.
> 
> Testing:
> The test builds were configured the following way:
> Linux 64bit (from patched and unpatched trunk):
> /path/to/configure --prefix=/prefix/gcc-vtv-bin-64
> --enable-libstdcxx-threads --enable-vtable-verify=yes
> MinGW 32bit cross compiled:
> /path/to/configure --target=i686-w64-mingw32
> --prefix=/prefix/mingw-vtv-bin-32 --with-gnu-ld --with-gnu-as
> --enable-fully-dynamic-string --disable-multilib
> --enable-libstdcxx-threads --enable-vtable-verify=yes
> MinGW 64bit cross compiled:
> /path/to/configure --target=x86_64-w64-mingw32
> --prefix=/prefix/mingw-vtv-bin-64 --with-gnu-ld --with-gnu-as
> --enable-fully-dynamic-string --disable-multilib
> --enable-libstdcxx-threads --enable-vtable-verify=yes
> Cygwin 64bit:
> /path/to/configure --enable-languages=c,c++ --enable-libstdcxx-threads
> --enable-vtable-verify=yes
> 
> At Linux the patched and unpatched version resulted in the same number
> of passed tests with 'make check-target-libvtv'.
> 
> Since MinGW was cross compiled the test cases couldn't be built and run
> with 'make check-target-libvtv'. Therefore they were built with the
> attached makefiles and tested afterwards on Windows 7 64bit. Some test
> cases contain Linux specific parts and weren't tested. See the makefiles
> for further information. Additionally virtual_func_test_min_UAF.cpp was
> also built and tested. All built tests passed.
> 
> Cygwin was just tested on gcc 4.9.0, because the current trunk isn't
> building for me. Even the clean trunk without the patch attached to this
> mail. On Cygwin with gcc 4.9.0 VTV worked.
> 
> Besides the test cases Botan was also built and tested (gcc 4.9.0) with
> MinGW 32bit and VTV.
> 
> regards
> 

-- 
Beste Grüße,
Patrick
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