https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78130
--- Comment #2 from Rian Quinn <rianquinn at gmail dot com> --- The output: Using built-in specs. COLLECT_GCC=/usr/bin/c++ Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.4.0-6ubuntu1~16.04.2' --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=new --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 --disable-werror --with-arch-32=i686 --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 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.2) COLLECT_GCC_OPTIONS='-D' 'GSL_THROW_ON_CONTRACT_VIOLATION' '-I' '/home/user/gsl/build' '-I' '/home/user/gsl/tests/..' '-I' '/home/user/gsl/tests/./unittest-cpp' '-v' '-save-temps' '-fno-strict-aliasing' '-std=c++14' '-O3' '-Wall' '-Wno-missing-braces' '-o' 'CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-linux-gnu/5/cc1plus -E -quiet -v -I /home/user/gsl/build -I /home/user/gsl/tests/.. -I /home/user/gsl/tests/./unittest-cpp -imultiarch x86_64-linux-gnu -D_GNU_SOURCE -D GSL_THROW_ON_CONTRACT_VIOLATION /home/user/gsl/tests/string_span_tests.cpp -mtune=generic -march=x86-64 -std=c++14 -Wall -Wno-missing-braces -fno-strict-aliasing -O3 -fpch-preprocess -fstack-protector-strong -Wformat-security -o string_span_tests.ii ignoring duplicate directory "/usr/include/x86_64-linux-gnu/c++/5" ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/5/../../../../x86_64-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /home/user/gsl/build /home/user/gsl/tests/.. /home/user/gsl/tests/./unittest-cpp /usr/include/c++/5 /usr/include/x86_64-linux-gnu/c++/5 /usr/include/c++/5/backward /usr/lib/gcc/x86_64-linux-gnu/5/include /usr/local/include /usr/lib/gcc/x86_64-linux-gnu/5/include-fixed /usr/include/x86_64-linux-gnu /usr/include End of search list. COLLECT_GCC_OPTIONS='-D' 'GSL_THROW_ON_CONTRACT_VIOLATION' '-I' '/home/user/gsl/build' '-I' '/home/user/gsl/tests/..' '-I' '/home/user/gsl/tests/./unittest-cpp' '-v' '-save-temps' '-fno-strict-aliasing' '-std=c++14' '-O3' '-Wall' '-Wno-missing-braces' '-o' 'CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-linux-gnu/5/cc1plus -fpreprocessed string_span_tests.ii -quiet -dumpbase string_span_tests.cpp -mtune=generic -march=x86-64 -auxbase-strip CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o -O3 -Wall -Wno-missing-braces -std=c++14 -version -fno-strict-aliasing -fstack-protector-strong -Wformat-security -o string_span_tests.s GNU C++14 (Ubuntu 5.4.0-6ubuntu1~16.04.2) version 5.4.0 20160609 (x86_64-linux-gnu) compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C++14 (Ubuntu 5.4.0-6ubuntu1~16.04.2) version 5.4.0 20160609 (x86_64-linux-gnu) compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 15157934e8203caff79287fd8f2d2843 /home/user/gsl/tests/string_span_tests.cpp: In member function ‘virtual void Suitestring_span_tests::Testzstring::RunImpl() const’: /home/user/gsl/tests/string_span_tests.cpp:865:329: warning: assuming signed overflow does not occur when assuming that (X - c) > X is always false [-Wstrict-overflow] In file included from /home/user/gsl/tests/../gsl/string_span:24:0, from /home/user/gsl/tests/string_span_tests.cpp:19: /home/user/gsl/tests/../gsl/span:475:9: warning: assuming signed overflow does not occur when assuming that (X - c) > X is always false [-Wstrict-overflow] Expects(count >= 0 && count <= size()); ^ /home/user/gsl/tests/string_span_tests.cpp: In member function ‘virtual void Suitestring_span_tests::Testwzstring::RunImpl() const’: /home/user/gsl/tests/string_span_tests.cpp:922:335: warning: assuming signed overflow does not occur when assuming that (X - c) > X is always false [-Wstrict-overflow] In file included from /home/user/gsl/tests/../gsl/string_span:24:0, from /home/user/gsl/tests/string_span_tests.cpp:19: /home/user/gsl/tests/../gsl/span:475:9: warning: assuming signed overflow does not occur when assuming that (X - c) > X is always false [-Wstrict-overflow] Expects(count >= 0 && count <= size()); ^ COLLECT_GCC_OPTIONS='-D' 'GSL_THROW_ON_CONTRACT_VIOLATION' '-I' '/home/user/gsl/build' '-I' '/home/user/gsl/tests/..' '-I' '/home/user/gsl/tests/./unittest-cpp' '-v' '-save-temps' '-fno-strict-aliasing' '-std=c++14' '-O3' '-Wall' '-Wno-missing-braces' '-o' 'CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64' as -v -I /home/user/gsl/build -I /home/user/gsl/tests/.. -I /home/user/gsl/tests/./unittest-cpp --64 -o CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o string_span_tests.s GNU assembler version 2.26.1 (x86_64-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.26.1 COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/ LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS='-D' 'GSL_THROW_ON_CONTRACT_VIOLATION' '-I' '/home/user/gsl/build' '-I' '/home/user/gsl/tests/..' '-I' '/home/user/gsl/tests/./unittest-cpp' '-v' '-save-temps' '-fno-strict-aliasing' '-std=c++14' '-O3' '-Wall' '-Wno-missing-braces' '-o' 'CMakeFiles/string_span_tests.dir/string_span_tests.cpp.o' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64'