linker error not detected, when using "--no-undefined" linker option

[gunrot]

I use cmake 3.12.1 and ninja (1.8.2). When using Wl,--no-undefined -Wl,--no-allow-shlib-undefined linker options, a linker error is not recognized by ninja, error code is 0. Using Unix Makefiles generator works as expected.
Sample code is here: ninjabug.zip

 cmake --build . || echo "error"
[1/1] : && /usr/bin/c++ -fPIC -Wl,--no-as-needed  -Wl,--no-undefined -Wl,--no-allow-shlib-undefined -shared -Wl,-soname,libninjabug.so -o libninjabug.so CMakeFiles/ninjabug.dir/ninjabug.cpp.o   && /usr/bin/cmake -E __run_co_compile --lwyu=libninjabug.so || true && :
CMakeFiles/ninjabug.dir/ninjabug.cpp.o: In function `ninjabug()':
ninjabug.cpp:(.text+0x5): undefined reference to `HelloWorld()'
collect2: error: ld returned 1 exit status

Using Makefiles is like this:

 cmake --build . || echo "error"
[ 50%] Linking CXX shared library libninjabug.so
CMakeFiles/ninjabug.dir/ninjabug.cpp.o: In function `ninjabug()':
ninjabug.cpp:(.text+0x5): undefined reference to `HelloWorld()'
collect2: error: ld returned 1 exit status
CMakeFiles/ninjabug.dir/build.make:83: recipe for target 'libninjabug.so' failed
make[2]: *** [libninjabug.so] Error 1
CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/ninjabug.dir/all' failed
make[1]: *** [CMakeFiles/ninjabug.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
error

[mathstuf]

This might be a CMake issue.

[mathstuf]

Hmm, ninja itself is returning success here:

% cmake --build .
[0-1->2/2@24.4] Linking CXX shared library libninjabug.so
/usr/bin/ld: CMakeFiles/ninjabug.dir/ninjabug.cpp.o: in function `ninjabug()':
ninjabug.cpp:(.text+0x5): undefined reference to `HelloWorld()'
collect2: error: ld returned 1 exit status
% echo 0
0
% ninja
[0-1->1/1@125000.0] Linking CXX shared library libninjabug.so
/usr/bin/ld: CMakeFiles/ninjabug.dir/ninjabug.cpp.o: in function `ninjabug()':
ninjabug.cpp:(.text+0x5): undefined reference to `HelloWorld()'
collect2: error: ld returned 1 exit status
% echo 0
0

But this is due to this being the rule for the link step:

  command = $PRE_LINK && /usr/lib64/ccache/c++ -fPIC $LANGUAGE_COMPILE_FLAGS $ARCH_FLAGS $LINK_FLAGS -shared $SONAME_FLAG$SONAME -o $TARGET_FILE $in $LINK_PATH $LINK_LIBRARIES && /usr/bin/cmake -E __run_co_compile --lwyu=libninjabug.so || true && $POST_BUILD

The || true is probably the problem. Please refile on CMake's issue tracker.

[mathstuf]

Specifically, it seems to be an issue with CMAKE_LINK_WHAT_YOU_USE being set to ON.

[jhasse]

Closing as it seems to be a CMake issue. Btw: Run ninja with -v to see the command that was run.

[mathstuf]

Filed here.