Here a sample code:

#include <stdio.h>
int main() {
    char input[80];
    while (fgets(input, 80, stdin) != NULL) {
        // nop
    }
    fgets(input, 80, stdin);
    printf("%s\n", input);
    return 0;
}

After sending EOF to exit the loop, the second fgets returns immediately return NULL, no second input possible. Compiling on 2.27 works as expected. Compiling on a 2.27 system with -static and executing on a 2.29 System also works.

I have no more glibc versions to check more. Only can say bugged on 2.29, works on 2.27.