[Bug libstdc++/66262] [REGRESSION] testsuite failure with libstdc++ (gcc-5) and g++-4.9 together

["costamagnagianfranco at yahoo dot it" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66262

--- Comment #6 from Gianfranco <costamagnagianfranco at yahoo dot it> ---
Created attachment 35662
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35662&action=edit
"Reduced" testcase

I tried in the last few days to reduce as much as possible the testcase.
I really hope it is enough for you to understand something more :)

to reproduce:
pbuilder-dist sid create
pbuilder-dist sid login
apt-get install vim cmake
apt-get install libboost-chrono-dev libboost-system-dev libboost-locale-dev
libboost-filesystem-dev 
apt-get install g++-5
cd casablanca/
mkdir build
cd build/
cmake .. && make test_runner streams_test -j 9 && cd Binaries/ && ./test_runner
libstreams_test.so
#FAILURE
cd ../..
mkdir build-gcc5
cd build-gcc5
export CXX=g++-5
cmake .. && make test_runner streams_test -j 9 && cd Binaries/ && ./test_runner
libstreams_test.so
#SUCCESS


the build needs unittestpp to create the unittest, and needs the "test_runner"
to open the library .so to run tests inside.

The bug is for sure in the libstreams_test.so, created from this source file
tests/functional/streams/fstreambuf_tests.cpp

I guess this because copying the .so built in gcc-5 directory in the gcc-4 one
makes the testsuite pass the tests.

I can provide the binaries if needed, unfortunately I don't know how to debug
the library inside, since it is called with dlopen.


g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.9.2-19'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-19) 


g++-5 -v
Using built-in specs.
COLLECT_GCC=g++-5
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 5.1.1-8'
--with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=c++98 --disable-libstdcxx-dual-abi
--enable-gnu-unique-object --disable-vtable-verify --enable-libmpx
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 5.1.1 20150528 (Debian 5.1.1-8) 


copying libstdc++6 from an ubuntu machine makes the test successfully pass on
the gcc-4 build.
(don't know how much of this is helpful for you)

thanks a lot,

Gianfranco