C++ – Adding external library into Qt Creator project

cqtqt-creatorwinapi

How can I add external library into a project built by Qt Creator RC1 (version 0.9.2)? For example, the win32 function EnumProcesses() requires Psapi.lib to be added in the project to build.

Best Answer

The proper way to do this is like this:

LIBS += -L/path/to -lpsapi

This way it will work on all platforms supported by Qt. The idea is that you have to separate the directory from the library name (without the extension and without any 'lib' prefix). Of course, if you are including a Windows specific lib, this really doesn't matter.

In case you want to store your lib files in the project directory, you can reference them with the $$_PRO_FILE_PWD_ variable, e.g.:

LIBS += -L"$$_PRO_FILE_PWD_/3rdparty/libs/" -lpsapi

Related Solutions

How to add include path in Qt Creator

If you are using qmake, the standard Qt build system, just add a line to the .pro file as documented in the qmake Variable Reference:

INCLUDEPATH += <your path>

If you are using your own build system, you create a project by selecting "Import of Makefile-based project". This will create some files in your project directory including a file named <your project name>.includes. In that file, simply list the paths you want to include, one per line. Really all this does is tell Qt Creator where to look for files to index for auto completion. Your own build system will have to handle the include paths in its own way.

As explained in the Qt Creator Manual, <your path> must be an absolute path, but you can avoid OS-, host- or user-specific entries in your .pro file by using $$PWD which refers to the folder that contains your .pro file, e.g.

INCLUDEPATH += $$PWD/code/include

C++ – Using External Lib/DLLs in Qt Creator

Compiling external libraries with QtCreator/gcc

If you own the source code of your libraries this is the .pro file to make an external library (.dll and .a) or Framework (on Mac OS X) from them:

TEMPLATE = lib

INCLUDEPATH = <your-include-paths>
HEADERS += <your-headers>
SOURCES += <your-sources>
TARGET = MyLib  /* The name of your libary */

/* Win32: To generate a MyLib.dll and libMyLib.a (gcc) or MyLib.lib (MSVC) file */
win32 {
    CONFIG += dll
}

/* Just in case you need to generate Mac Frameworks: */
macx {
    CONFIG += shared lib_bundle
    FRAMEWORK_HEADERS.version = Versions
    FRAMEWORK_HEADERS.files += <your library headers>
    /* Example:
    FRAMEWORK_HEADERS.files += /path/to/your/lib/MyLib.h
    */
    FRAMEWORK_HEADERS.path = Headers
    QMAKE_BUNDLE_DATA = FRAMEWORK_HEADERS
    VERSION = 0.5.0   // a framework version you can define
}

Adding external libraries to your QtCreator/gcc project

/* your project settings */

/* If you compile on windows */
win32 {
    /* If you compile with QtCreator/gcc: */
    win32-g++:LIBS += /path/to/your/libMyLib.a

    /* IF you compile with MSVC: */
    win32-msvc:LIBS += /path/to/your/libMyLib.lib
}

/* If compile on Mac and want to link against a framework */
macx {
    LIBS+= -framework MyLib
    QMAKE_FLAGS += -F/path/to/MyLib
}

Note that to use external libraries with gcc you need the libMyLib.a file that contains the linking information. The libMyLib.lib are generated by MS Visual Studio and can't be processed by gcc afaik!