Compilare: user.c: In function ‘buildPrefixTable’: user.c:41:5: warning: implicit declaration of function ‘strlen’ [-Wimplicit-function-declaration] int m = strlen(s1) - 1; ^ user.c:41:13: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] int m = strlen(s1) - 1; ^ user.c: In function ‘kmp’: user.c:61:14: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] int n = strlen(s2) - 1; ^