Undefined reference to clock_gettime, gcc 4.6 & cmake
You should ensure that -lpthread -lrt
appear after your libraries like ../lib/libLibUtil.a
hookenz
Updated on June 19, 2022Comments
-
hookenz almost 2 years
I'm having a link error under cmake that I don't have when compiling on a system with an older version of gcc.
The specific error is "undefined reference to
clock_gettime
" but-lrt
is appearing on the command line.My gcc version:
gcc (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1 Copyright (C) 2011 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
cmake version 2.8.5
I am including the required "-lrt" through target_link_libraries in my CMakeLists.txt file. I can see it appear in the compiler line with make VERBOSE=1
I've read that gcc 4.6 is picky about the position of link libraries on the command line.
How can I fix this for CMake?
EDIT: Link line
Linking CXX executable ../bin/obbsd cd /home/matt/Desktop/Matt/OBBS/Build/server && /usr/bin/cmake -E cmake_link_script \ CMakeFiles/obbsd.dir/link.txt --verbose=1 /usr/bin/c++ -g CMakeFiles/obbsd.dir/Block.cpp.o \ CMakeFiles/obbsd.dir/BlockFileCache.cpp.o \ CMakeFiles/obbsd.dir/BlockFileStore.cpp.o \ CMakeFiles/obbsd.dir/BlockMemoryCache.cpp.o \ CMakeFiles/obbsd.dir/BlockStore.cpp.o CMakeFiles/obbsd.dir/Config.cpp.o \ CMakeFiles/obbsd.dir/DeleteBlockSession.cpp.o \ CMakeFiles/obbsd.dir/mConfigFile.cpp.o \ CMakeFiles/obbsd.dir/mNetworkPacketReader.cpp.o \ CMakeFiles/obbsd.dir/mNetworkPacketWriter.cpp.o \ CMakeFiles/obbsd.dir/obbsd.cpp.o \ CMakeFiles/obbsd.dir/ReadBlockSession.cpp.o CMakeFiles/obbsd.dir/Server.cpp.o \ CMakeFiles/obbsd.dir/Session.cpp.o CMakeFiles/obbsd.dir/Utility.cpp.o \ CMakeFiles/obbsd.dir/WriteBlockSession.cpp.o -o ../bin/obbsd -rdynamic \ -lpthread -lrt ../lib/libLibUtil.a ../lib/libLibUtil.a(mTimer.cpp.o): In function `mTimer::GetTick()': /home/matt/Desktop/Matt/OBBS/LibUtil/src/mTimer.cpp:108: undefined reference to `clock_gettime'
Why is ../lib/libLibUtil.a appearing after -lrt when LibUtil (what would be libLibUtil.a) is before rt?
CMakeLists.txt includes...
... add_executable(obbsd ${SERVER_SOURCE_FILES}) find_package(Threads REQUIRED) target_link_libraries(obbsd ${CMAKE_THREAD_LIBS_INIT} LibUtil rt)