CMake: How to link against a static 3rd party lib?

Question

What I have: my code (simple main.cpp), headers of the 3rd party lib (EnvVar TPLIB_INCLUDE), binary lib (several .a files in TPLIB_BINARY_PATH) and the following CMakeLists.txt:

# current source directory: CMAKE_CURRENT_SOURCE_DIR
# current binary directory: CMAKE_CURRENT_BINARY_DIR

# require 2.6 to get support for the simple IF construct
CMAKE_MINIMUM_REQUIRED(VERSION 2.6.0)

PROJECT( simpleapp)
SET( PROGNAME simpleapp )

SET( CMAKE_COLOR_MAKEFILE ON )
SET( CMAKE_VERBOSE_MAKEFILE ON )
SET( CMAKE_INCLUDE_CURRENT_DIR TRUE )

# the actual .cpp files go here
SET(project_SOURCES
    main.cpp
)

# add here all files that need processing by Qt's MOC if there are any
set(project_MOC_SOURCES
    # files would go here
)

# add here all files that will be processed by Qt's UIC
set(project_UIS
    # all .ui files would go here
)

# additional Qt resources go here
set(project_RCCS
    # all .qrc files would go here
)

# setup Qt
FIND_PACKAGE(Qt4 REQUIRED)

INCLUDE(${QT_USE_FILE})

QT4_WRAP_CPP(test_MOCS ${project_MOC_SOURCES})
QT4_WRAP_UI(test_UIS_H ${project_UIS})
QT4_WRAP_CPP(test_MOC_UI ${project_UIS_H})
QT4_ADD_RESOURCES(test_RCC_SRCS ${project_RCCS})

include_directories( ${CMAKE_BINARY_DIR} $ENV{TPLIB_INCLUDE})

ADD_EXECUTABLE( ${PROGNAME} ${project_SOURCES} ${test_MOCS} ${test_RCC_SRCS} ${test_MOC_UI} )

link_directories($ENV{TPLIB_BINARY_PATH})

TARGET_LINK_LIBRARIES(${PROGNAME} ${QT_LIBRARIES} lib_misc lib_tools)

makeing the project creating the main.cpp.o works as usual. Thus CMake found the third party headers. When it comes to link ld complains cannot find -llib_misc and -llib_tools. Removing the "link_directories" line or specifiingy the libs absolute name leads to "No rule to make target /path/to/lib_misc.a"

So how to tell CMake to use these libs for linking only?

Answer 1

link_directories($ENV{TPLIB_BINARY_PATH}) should be placed before ADD_EXECUTABLE.

From the official documents of CMake, there are notes on link_directories:

The command will apply only to targets created after it is called.