Installing GTest and GMock - c++

Question

I have installed GTest and GMock on my Ubuntu 17.04 box. Broadly speaking installed as follows;
sudo apt-get install libgtest-dev
cmake CMakeLists.txt
make
I then sym linked the libraries creaetd in /usr/src in /usr/lib. (ie link in /usr/lib points to /usr/src)
I then did the same for GMock
sudo apt-get install -y google-mock
then cmake and make as above
Libraries sym linked as before.
I have created the following CMakeLists.txt
project(chapterFirstExample)
cmake_minimum_required(VERSION 2.6)
include_directories(/usr/include)
link_directories(/usr/lib)
add_definitions(-std=c++0x)
set(CMAKE_CXX_FLAGS "${CMAXE_CXX_FLAGS} -Wall")
set(sources
main.cpp
SoundexTest.cpp)
add_executable(tddTest ${sources})
target_link_libraries(tddTest pthread)
target_link_libraries(tddTest gmock)
target_link_libraries(tddTest gtest)
And have two source files
main.cpp
#include "gmock/gmock.h"
int main(int argc, char** argv) {
testing::InitGoogleMock(&argc, argv);
return RUN_ALL_TESTS();
}
SoundexTest.cpp
class Soundex
{
};
#include "gmock/gmock.h"
TEST(SoundexEncoding, RetainsSoleLetterOfOneLetterWord)
{
Soundex soundex;
}
(I am working through Jeff Langr's Modern C++ Programming with Test Driven Development book)
I run cmake on my CmakeLists.txt file, which runs without error. When I run make though I get this;
[ 33%] Linking CXX executable tddTest
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<testing::TestPartResultReporterInterface*>::~ThreadLocal()':
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEED2Ev[_ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEED5Ev]+0x24): undefined reference to `pthread_getspecific'
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEED2Ev[_ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEED5Ev]+0x39): undefined reference to `pthread_key_delete'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<std::vector<testing::internal::TraceInfo, std::allocator<testing::internal::TraceInfo> > >::~ThreadLocal()':
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEED2Ev[_ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEED5Ev]+0x24): undefined reference to `pthread_getspecific'
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEED2Ev[_ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEED5Ev]+0x39): undefined reference to `pthread_key_delete'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<std::vector<testing::internal::TraceInfo, std::allocator<testing::internal::TraceInfo> > >::GetOrCreateValue() const':
gtest-all.cc:(.text._ZNK7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE16GetOrCreateValueEv]+0x25): undefined reference to `pthread_getspecific'
gtest-all.cc:(.text._ZNK7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE16GetOrCreateValueEv]+0x88): undefined reference to `pthread_setspecific'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<testing::TestPartResultReporterInterface*>::CreateKey()':
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE9CreateKeyEv[_ZN7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE9CreateKeyEv]+0x27): undefined reference to `pthread_key_create'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<std::vector<testing::internal::TraceInfo, std::allocator<testing::internal::TraceInfo> > >::CreateKey()':
gtest-all.cc:(.text._ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE9CreateKeyEv[_ZN7testing8internal11ThreadLocalISt6vectorINS0_9TraceInfoESaIS3_EEE9CreateKeyEv]+0x27): undefined reference to `pthread_key_create'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gtest-all.cc.o): In function `testing::internal::ThreadLocal<testing::TestPartResultReporterInterface*>::GetOrCreateValue() const':
gtest-all.cc:(.text._ZNK7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE16GetOrCreateValueEv]+0x25): undefined reference to `pthread_getspecific'
gtest-all.cc:(.text._ZNK7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalIPNS_31TestPartResultReporterInterfaceEE16GetOrCreateValueEv]+0x88): undefined reference to `pthread_setspecific'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gmock-all.cc.o): In function `testing::internal::ThreadLocal<testing::Sequence*>::CreateKey()':
gmock-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_8SequenceEE9CreateKeyEv[_ZN7testing8internal11ThreadLocalIPNS_8SequenceEE9CreateKeyEv]+0x27): undefined reference to `pthread_key_create'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gmock-all.cc.o): In function `testing::internal::ThreadLocal<testing::Sequence*>::GetOrCreateValue() const':
gmock-all.cc:(.text._ZNK7testing8internal11ThreadLocalIPNS_8SequenceEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalIPNS_8SequenceEE16GetOrCreateValueEv]+0x25): undefined reference to `pthread_getspecific'
gmock-all.cc:(.text._ZNK7testing8internal11ThreadLocalIPNS_8SequenceEE16GetOrCreateValueEv[_ZNK7testing8internal11ThreadLocalIPNS_8SequenceEE16GetOrCreateValueEv]+0x88): undefined reference to `pthread_setspecific'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgmock.a(gmock-all.cc.o): In function `testing::internal::ThreadLocal<testing::Sequence*>::~ThreadLocal()':
gmock-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_8SequenceEED2Ev[_ZN7testing8internal11ThreadLocalIPNS_8SequenceEED5Ev]+0x24): undefined reference to `pthread_getspecific'
gmock-all.cc:(.text._ZN7testing8internal11ThreadLocalIPNS_8SequenceEED2Ev[_ZN7testing8internal11ThreadLocalIPNS_8SequenceEED5Ev]+0x39): undefined reference to `pthread_key_delete'
collect2: error: ld returned 1 exit status
CMakeFiles/tddTest.dir/build.make:120: recipe for target 'tddTest' failed
make[2]: *** [tddTest] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/tddTest.dir/all' failed
make[1]: *** [CMakeFiles/tddTest.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
I am new to cmake, and very rusty on make. This output though makes me feel thought that I have not built GTest or GMock correctly. Can anyone give some pointers please. (No pun intended)
Thanks

Answer 1

The order of libraries passed to the linker matters. When the linker sees a library file name, by default (*) it pulls in just the objects from that library which resolve one or more undefined symbols it knows are needed at that point.
So if a library A depends on a library B but you pass main.o -lB -lA to the linker, when it comes to -lB it will pull in some objects from B if they are needed by main.o, but then if A needs additional symbols from B, it will not go back and look for additional objects from B, so those needed symbols remain unresolved.
gmock depends on gtest, and gmock (and maybe gtest?) depend on pthread, so a better order for your libraries would be:
target_link_libraries(tddTest gtest)
target_link_libraries(tddTest gmock)
target_link_libraries(tddTest pthread)
(*) Some GNU ld linker options cause different behavior. In particular, --whole-archive -lsomething --no-whole-archive will force it to get ALL the contents from a library file, needed or not. --start-group -lA -lB -lC --end-group will cause it to repeatedly loop over a set of libraries until none of them can be used to resolve any more symbols for a whole loop. But most of the time, it's enough to just list the libraries you need so that the libraries that use other libraries come earlier in the list.