CODEWITHSUNDEEP
c++ccmakeexecute
Josch
Josch

Reputation: 121

How do I use function from external library?

I'm starting an OpenGL Application via glc-capture. glc is a c-library which hooks on the OpenGL buffer and x11 server. glc needs a key command in the OpenGL display to start recording the OpenGL output.

But my software should start recording the output programmatically, not via a key presses. The glc files are all too complex for my basic knowledge to understand them completely. But basically the structur seems to be the following:

The glc-capture is a shell script which does some settings and executes LD_PRELOAD=libglc-capture.so "${@}". x11.c contains the x11 hook which listens for key events. There are some initializations going on. On a special key event the function start_capture() is executed by x11.c. start_capture() is defined in a file lib.h and implemented in the main.c file.

My questions: How can I execute the start_capture() function on my own c++ application? I tried link the libraries (hook and capture) via CMakeList.txt and include the header file, but that always leaves me at "undefined reference: start_capture()".

Here is the line from CMakeList.txt which links the libraries:

target_link_libraries(${PROJECT_NAME} ${QT_LIBRARIES} libglc-hook.so libglc-capture.so libglc-core.so libglc-export.so)

EDIT2: Here is the error I get at runtime:

/opt/ros/fuerte/stacks/visualization/rviz/bin/rviz: symbol lookup error: /home/jrick/fuerte_workspace/sandbox/Bag2Film/lib/libBag2Film.so: undefined symbol: start_capture

The output from nm:

jrick@robot2:~/fuerte_workspace/sandbox/Bag2Film/lib$ nm libBag2Film.so | grep capture

0000000000003a30 t start_capture

0000000000003790 t stop_capture

Upvotes: 0

Views: 2752

Answers (1)

Axel
Axel

Reputation: 14169

I don't know about glc-capture, but from what you say it should be possible to linke your application directly against libglc-capture (try passing -lglc-capture as a linker flag). Consult the libraries documentation if that doesn't work.

In addition, you would have to include a header file that includes the declaration of start_capture. Again, consult the library documentation to find out about which file to use. If there's no header present, you can still declare it yourself (sounds like a C-library, so something along the line extern "C" { void start_capture(); } might do it.

If your project still compiles and links after these changes, add a call to start_capture() where you need it.

Come back here if it doesn't help.

Upvotes: 2

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