Compilare: user.cpp: In function ‘int main()’: user.cpp:47:24: warning: left operand of comma operator has no effect [-Wunused-value] for(i = M, j = N;i > 0, j > 0;) { ^ user.cpp: In function ‘char next()’: user.cpp:15:41: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf, 1, BUF, fin), pos = 0; ^