Cmake to link OpenSSL getting error `cannot find -l1` [duplicate] - c++

Question

I'm running RHEL 5.1 and use gcc.
How I tell cmake to add -pthread to compilation and linking?

Answer 1

#Manuel was part way there. You can add the compiler option as well, like this:
If you have CMake 3.1.0+, this becomes even easier:
set(THREADS_PREFER_PTHREAD_FLAG ON)
find_package(Threads REQUIRED)
target_link_libraries(my_app PRIVATE Threads::Threads)
If you are using CMake 2.8.12+, you can simplify this to:
find_package(Threads REQUIRED)
if(THREADS_HAVE_PTHREAD_ARG)
target_compile_options(my_app PUBLIC "-pthread")
endif()
if(CMAKE_THREAD_LIBS_INIT)
target_link_libraries(my_app "${CMAKE_THREAD_LIBS_INIT}")
endif()
Older CMake versions may require:
find_package(Threads REQUIRED)
if(THREADS_HAVE_PTHREAD_ARG)
set_property(TARGET my_app PROPERTY COMPILE_OPTIONS "-pthread")
set_property(TARGET my_app PROPERTY INTERFACE_COMPILE_OPTIONS "-pthread")
endif()
if(CMAKE_THREAD_LIBS_INIT)
target_link_libraries(my_app "${CMAKE_THREAD_LIBS_INIT}")
endif()
If you want to use one of the first two methods with CMake 3.1+, you will need set(THREADS_PREFER_PTHREAD_FLAG ON) there too.

Answer 2

The following should be clean (using find_package) and work (the find module is called FindThreads):
cmake_minimum_required (VERSION 2.6)
find_package (Threads)
add_executable (myapp main.cpp ...)
target_link_libraries (myapp ${CMAKE_THREAD_LIBS_INIT})

Answer 3

Here is the right anwser:
ADD_EXECUTABLE(your_executable ${source_files})
TARGET_LINK_LIBRARIES( your_executable
pthread
)
equivalent to
-lpthread

Answer 4

target_compile_options solution above is wrong, it won't link the library.
Use:
SET(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -pthread")
OR
target_link_libraries(XXX PUBLIC pthread)
OR
set_target_properties(XXX PROPERTIES LINK_LIBRARIES -pthread)