I'm using Keil uVision version 4.73. In my Options for Target I select RTX Kernel Operating System. This selection will add following to the Linker Control String in the Linker Tab:
C:\Keil\ARM\RV31\LIB\RTX_ARM_L.LIB This means this operating system library will be linked when I build my project. In addition to linking this library, I have added all files used to create this library to my project as follows:
rt_Event.c HAL_ARM.c ...
These files are in C:\Keil\ARM\RL\RTX\SRC\ARM folder.
Why does my build work ? I'm including same Operating System twice. Shouldn't I get re-defined symbols ?
Libraries are the spare parts store where the linker looks for all the bolts and pieces it doesn't manage to find in all your object files.
You would have a hard time to make your own printf() if you got a linker error from the library.
Thanks for making it easy to understand.