Compilare: user.cpp: In function ‘int compara(char*, char*)’: user.cpp:23:89: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while((s1[l]==s2[l] || s1[l]-s2[l]=='a'-'A' || s2[l]-s1[l]=='a'-'A') && l<=strlen(s1)) ^ user.cpp:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(l-1==strlen(s1)) { ^ user.cpp:32:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(l-1==strlen(s2)) { ^ user.cpp: In function ‘int prefix(char*, char*)’: user.cpp:52:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<=strlen (s1)-1;i++) ^ user.cpp: In function ‘int compara(char*, char*)’: user.cpp:47:1: warning: control reaches end of non-void function [-Wreturn-type] } ^