undefined reference to 'ws2811_...'

[R3tr0BoiDX]

I did installed the library as described in the README by doing

cd build
cmake -D BUILD_SHARED=ON -D BUILD_TEST=OFF ..
cmake --build .
sudo make install


==> It says:

[100%] Built target ws2811
Install the project...
-- Install configuration: ""
-- Installing: /usr/local/lib/libws2811.so
-- Installing: /usr/local/include/ws2811/ws2811.h
-- Installing: /usr/local/include/ws2811/rpihw.h
-- Installing: /usr/local/include/ws2811/pwm.h
-- Installing: /usr/local/include/ws2811/clk.h
-- Installing: /usr/local/include/ws2811/dma.h
-- Installing: /usr/local/include/ws2811/gpio.h
-- Installing: /usr/local/include/ws2811/mailbox.h
-- Installing: /usr/local/include/ws2811/pcm.h
-- Installing: /usr/local/lib/pkgconfig/libws2811.pc

However, if I want to compile my code with gcc main.c -o test, I get main.c:(.text+0x18): undefined reference to 'ws2811_fini' for example.

My main.c:
#include <ws2811/ws2811.h> int main(int argc, char const *argv[]) { return 0; }

[Gadgetoid]

The header file "declares" all the functions you're using, but the object file or library is responsible for "defining" them.

You need to add -lws2811 to instruct gcc to link against the ws2812 library and include the definitions of ws2811_fini. In the simplest sense this either smooshes your code and the library code together into a single executable (static linking) or allows gcc to create a binary that knows where to find the library file dynamic linking).

So:

gcc main.c -lws2811 -o test

[KC5-BP]

Hello LED pals ;)

In advance, if you encounter that issue after linking the -lws2811 ('cause I did) :
$ gcc main.c -lws2811 -o test
/usr/bin/ld: /usr/local/lib/libws2811.a(ws2811.c.o): in function ws2811_set_custom_gamma_factor:
ws2811.c:(.text+0x2934): undefined reference to pow
collect2: error: ld returned 1 exit status

Just link the math lib. into the cmd as follow :
$ gcc main.c -lws2811 -lm -o test