Compilare: user.c: In function ‘calculate’: user.c:31:16: warning: implicit declaration of function ‘pow’ [-Wimplicit-function-declaration] return pow(10,18); ^ user.c:31:16: warning: incompatible implicit declaration of built-in function ‘pow’ user.c:31:16: note: include ‘<math.h>’ or provide a declaration of ‘pow’ user.c:74:12: warning: implicit declaration of function ‘fabs’ [-Wimplicit-function-declaration] if(fabs(1.0*arr_second[i].x - arr[mid].x) <= dis_minim){ ^ user.c:74:12: warning: incompatible implicit declaration of built-in function ‘fabs’ user.c:74:12: note: include ‘<math.h>’ or provide a declaration of ‘fabs’ user.c: In function ‘main’: user.c:97:5: warning: implicit declaration of function ‘mergeSort’ [-Wimplicit-function-declaration] mergeSort(arr, 1, n); ^ user.c:106:21: warning: implicit declaration of function ‘sqrt’ [-Wimplicit-function-declaration] printf("%.8f\n",sqrt(answer)); ^ user.c:106:21: warning: incompatible implicit declaration of built-in function ‘sqrt’ user.c:106:21: note: include ‘<math.h>’ or provide a declaration of ‘sqrt’ user.c:88:14: warning: variable ‘g’ set but not used [-Wunused-but-set-variable] FILE *f,*g; ^ user.c: At top level: user.c:110:6: warning: conflicting types for ‘mergeSort’ void mergeSort(PUNCT a[], int left, int right) ^ user.c:97:5: note: previous implicit declaration of ‘mergeSort’ was here mergeSort(arr, 1, n); ^ user.c: In function ‘main’: user.c:92:5: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ user.c:94:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&arr[i].x, &arr[i].y); ^