On 2019-11-15 15:25, Arthur Norman wrote: >> I notice that you are not independently compiling your source files and have >> no >> include guard in t.h. >> Could I suggest that you add the include guard to t.h and retest. >> If you still have an issue, try independently compiling your source files, >> then >> linking them as a separate step, to see if that works. >> You could also test reproducing the issue on another gcc platform, under a >> Unix >> VM, or a WSL Linux distro. > > I attach a versiuon of the test with an include guard and with t1.cpp and > t2.cpp > compiled in separate invocations of g++ - I still see the multiple definition. > > ${1:-g++} -std=c++17 -I. -c t1.cpp > ${1:-g++} -std=c++17 -I. -c t2.cpp > ${1:-g++} -std=c++17 t1.o t2.o -o t > /usr/lib/gcc/x86_64-pc-cygwin/8.3.0/../../../../x86_64-pc-cygwin/bin/ld: > t2.o:t2.cpp:(.text+0x86): multiple definition of `TLS init function for > Data::valref'; t1.o:t1.cpp:(.text+0x4a): first defined here > collect2: error: ld returned 1 exit status > ./t > > As per my original posting before enquiring here I had tried on a 64-bit > ubuntu > machine, on a Macbook (where it is clang not g++, but I invoke the compiler as > g++) and on a Raspberry pi.
Sorry missed that. > The original code I had pain with was with include guards and all files > compiled > independently via make - the test casee I submitted had perhaps tried to hard > to > shorten and simplify. > > I also tried both 32 and 64-bit mingw compilers under cygwin - making that > easier is why the test script goes ${1:-g++} so I can override the compiler > selection to be x86_64-w64-mingw32-g++ or the i686 variant. Those both show > the > multiple definition problem. That points to a common problem with the loader generating Windows PEs: it is possible that is a Windows limitation. As ld is part of binutils, you might want to try searching and posting on that mailing list, conveniently located just next door: https://sourceware.org/binutils/ http://sourceware.org/ml/binutils/ http://lists.gnu.org/archive/html/bug-binutils/ before looking further at gcc. Please emphasize clearly that this works successfully with ELF executables on Unix platforms, and list those; and ld fails only with Windows (PE) executables using Cygwin and Mingw 32/64 tool chains, and list those; and include the test code, commands and results on each platform, to clearly demonstrate the issue. Use a specific subject to get appropriate attention and a relevant response e.g. "ld fails only for Windows PE with multiple definition of TLS init function". -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple