Compilare: user.c: In function ‘main’: user.c:19:19: warning: implicit declaration of function ‘strlen’ [-Wimplicit-function-declaration] int cap = strlen(str); ^~~~~~ user.c:19:19: warning: incompatible implicit declaration of built-in function ‘strlen’ user.c:19:19: note: include ‘<string.h>’ or provide a declaration of ‘strlen’ user.c:7:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("laundering.in", "rt", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:8:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("laundering.out", "wt", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:10:5: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", &aSize); ^~~~~~~~~~~~~~~~~~~ user.c:17:9: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", str); ^~~~~~~~~~~~~~~~