Eroare de compilare: user.c: In function ‘back’: user.c:16: error: ‘for’ loop initial declarations are only allowed in C99 mode user.c:16: note: use option -std=c99 or -std=gnu99 to compile your code user.c:39: error: ‘for’ loop initial declarations are only allowed in C99 mode user.c: In function ‘main’: user.c:54: error: ‘for’ loop initial declarations are only allowed in C99 mode user.c:55: error: ‘bool’ undeclared (first use in this function) user.c:55: error: (Each undeclared identifier is reported only once user.c:55: error: for each function it appears in.) user.c:55: error: expected ‘;’ before ‘is_prime’ user.c:56: error: ‘for’ loop initial declarations are only allowed in C99 mode user.c:57: error: ‘is_prime’ undeclared (first use in this function) user.c:57: error: ‘false’ undeclared (first use in this function) user.c:73: error: redefinition of ‘i’ user.c:54: note: previous definition of ‘i’ was here user.c:73: error: ‘for’ loop initial declarations are only allowed in C99 mode user.c:66: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:67: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:70: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result