Square of a number being defined using #define

by

square is under-parenthesized: it expands textually, so

#define square(x) x*x
   ...
i=4/square(4);

means

i=4/4*4;

which groups as (4/4) * 4. To fix, add parentheses:

#define square(x) ((x)*(x))

Still a very iffy #define as it evaluates x twice, so square(somefun()) calls the function twice and does not therefore necessarily compute a square but rather the product of the two successive calls, of course;-).

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