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cc89

Error: implicit declaration of function [c]

I included math.h library and used abs function and this error shows:

error: implicit declaration of function ‘abs’ [-Werror=implicit-function-declaration]
razlika=(abs(x3) / ((x1+x2)/2))*100;
^
cc1: some warnings being treated as errors
Solution

  • Include stdlib.h, not math.h.

    Implicit declaration errors are generally due to missing/incorrect header files.