If you are not sure whether you have found a bug, here are some guidelines:
If the debugger gets a fatal signal, for any input whatever, that is a
GDB bug. Reliable debuggers never crash.
If GDB produces an error message for valid input, that is a
bug. (Note that if you’re cross debugging, the problem may also be
somewhere in the connection to the target.)
If GDB does not produce an error message for invalid input,
that is a bug. However, you should note that your idea of
“invalid input” might be our idea of “an extension” or “support
for traditional practice”.
If you are an experienced user of debugging tools, your suggestions
for improvement of GDB are welcome in any case.