Re: gdb emacs reporting 'Function "x_error_quitter" not defined'

[Richard Stallman]

    The code produced by GCC under -O0 is totally unoptimized: e.g., it
    reloads registers even if the required value is already there, doesn't
    remove loop-invariant code out of the loops, etc.  It's really very
    different.

Those differences should not affect the meaning of correct C code.
Indeed, we use some constructs that are not entirely defined, according
to standard C.  However, given the optimizations GCC actually does,
they rarely change meaning when we enable or disable optimization.
Practically speaking, this issue is not large enough for attention.