[PPL-devel] FW: seg fault on override of a weak symbol in g++

[Roberto Bagnara]

On 08/05/14 01:07, Keith Clifford wrote:
> This is just an update about the Seg Fault that I had building PPL last
> week. The issue is in the mingw compiler under certain circumstances which
> are described below if you're interested and in the attached files. The
> compiler and your test in the configure script indicate that the compiler
> supports weak symbols but it really doesn't under specific circumstances
> which the PPL build found. Anyway its in Cygwin's hands now.

Hello Keith.

thanks for the update.  Please keep me posted.  I am thinking that,
even if Cygwin people fixes the issue, this will not happen until
some time.  Perhaps we should change the configure script so as
to perform a more precise detection.  What do you think?
Thanks again,

   Roberto

> -----Original Message-----
> From: Keith Clifford [mailto:kclifford at tranaptic.ca] 
> Sent: August 4, 2014 2:10 PM
> To: 'cygwin at cygwin.com'
> Subject: seg fault on override of a weak symbol in g++
> 
> Hi,
> I was trying to build the ppl 1.1 library and got a seg fault when running
> one of the tests. I've narrowed it down to the attached test case.
> 
> System: CYGWIN_NT-6.1 Keith-PC 1.7.31(0.272/5/3) 2014-07-25 11:26 x86_64
> Cygwin
> 
> Both the following GCC's exhibit the problem Cygwin:
> Using built-in specs.
> COLLECT_GCC=i686-pc-mingw32-g++
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-pc-mingw32/4.7.3/lto-wrapper.exe
> Target: i686-pc-mingw32
> Configured with:
> /usr/src/packages/mingw-gcc/64/mingw-gcc-4.7.3-1/src/gcc-4.7.3/configure
> --srcdir=/usr/src/packages/mingw-gcc/64/mingw-gcc-4.7.3-1/src/gcc-4.7.3
> --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin
> --libexecdir=/usr/lib --datadir=/usr/share --localstatedir=/var
> --sysconfdir=/etc --datarootdir=/usr/share --docdir=/usr/share/doc/mingw-gcc
> -C --build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=i686-pc-mingw32
> --without-libiconv-prefix --without-libintl-prefix
> --with-sysroot=/usr/i686-pc-mingw32/sys-root
> --with-build-sysroot=/usr/i686-pc-mingw32/sys-root
> --enable-languages=c,c++,fortran,objc,obj-c++ --disable-sjlj-exceptions
> --with-dwarf2 --enable-shared --enable-libgomp --disable-win32-registry
> --enable-libstdcxx-debug --disable-build-poststage1-with-cxx
> --enable-version-specific-runtime-libs --disable-multilib
> --enable-decimal-float=bid --disable-werror --enable-lto Thread model: win32
> gcc version 4.7.3 (GCC)
> 
> Using built-in specs.
> COLLECT_GCC=i686-w64-mingw32-g++
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-w64-mingw32/4.8.3/lto-wrapper.exe
> Target: i686-w64-mingw32
> Configured with:
> /cygdrive/i/szsz/tmpp/cygwin64/mingw64-i686/mingw64-i686-gcc-4.8.3-1/src/gcc
> -4.8.3/configure
> --srcdir=/cygdrive/i/szsz/tmpp/cygwin64/mingw64-i686/mingw64-i686-gcc-4.8.3-
> 1/src/gcc-4.8.3 --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin
> --sbindir=/usr/sbin --libexecdir=/usr/libexec --datadir=/usr/share
> --localstatedir=/var --sysconfdir=/etc --libdir=/usr/lib
> --datarootdir=/usr/share --docdir=/usr/share/doc/mingw64-i686-gcc
> --htmldir=/usr/share/doc/mingw64-i686-gcc/html -C --build=x86_64-pc-cygwin
> --host=x86_64-pc-cygwin --target=i686-w64-mingw32 --without-libiconv-prefix
> --without-libintl-prefix --with-sysroot=/usr/i686-w64-mingw32/sys-root
> --with-build-sysroot=/usr/i686-w64-mingw32/sys-root --disable-multilib
> --disable-win32-registry
> --enable-languages=c,ada,c++,fortran,lto,objc,obj-c++
> --enable-fully-dynamic-strings --enable-graphite --enable-libgomp
> --enable-libquadmath --enable-libquadmath-support --enable-libssp
> --enable-version-specific-runtime-libs --with-dwarf2 --with-gnu-ld
> --with-gnu-as --with-tune=generic
> --with-cloog-include=/usr/include/cloog-isl --with-system-zlib
> --libexecdir=/usr/lib Thread model: win32 gcc version 4.8.3 (GCC)
> 
> 
> When built with the default Cygwin compiler the problem doesn't occur.
> Using built-in specs.
> COLLECT_GCC=g++
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/4.8.3/lto-wrapper.exe
> Target: x86_64-pc-cygwin
> Configured with:
> /cygdrive/i/szsz/tmpp/cygwin64/gcc/gcc-4.8.3-2/src/gcc-4.8.3/configure
> --srcdir=/cygdrive/i/szsz/tmpp/cygwin64/gcc/gcc-4.8.3-2/src/gcc-4.8.3
> --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin
> --libexecdir=/usr/libexec --datadir=/usr/share --localstatedir=/var
> --sysconfdir=/etc --libdir=/usr/lib --datarootdir=/usr/share
> --docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C
> --build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin
> --without-libiconv-prefix --without-libintl-prefix --enable-shared
> --enable-shared-libgcc --enable-static
> --enable-version-specific-runtime-libs --enable-bootstrap
> --disable-__cxa_atexit --with-dwarf2 --with-tune=generic
> --enable-languages=ada,c,c++,fortran,lto,objc,obj-c++ --enable-graphite
> --enable-threads=posix --enable-libatomic --enable-libgomp --disable-libitm
> --enable-libquadmath --enable-libquadmath-support --enable-libssp
> --enable-libada --enable-libgcj-sublibs --disable-java-awt --disable-symvers
> --with-ecj-jar=/usr/share/java/ecj.jar --with-gnu-ld --with-gnu-as
> --with-cloog-include=/usr/include/cloog-isl --without-libiconv-prefix
> --without-libintl-prefix --with-system-zlib --libexecdir=/usr/lib Thread
> model: posix gcc version 4.8.3 (GCC)
> 
> In the attached files in weak.cpp if the line
> 	static ios_base::Init __ioinit;
> is commented out the seg fault doesn't occur. Doing a disassembly of weak.o
> (objdump -d weak.o) shows that the call includes a nonzero offset that gets
> applied when the weak symbol is overridden by the function in strong.o. The
> offset is zero if the above mentioned line is commented out. 
> 
> Regards,
> Keith
> 
> 


-- 
     Prof. Roberto Bagnara

Applied Formal Methods Laboratory - University of Parma, Italy
mailto:bagnara at cs.unipr.it
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