[distcc] gcc bootstraps with distcc

[Zack Weinberg]

Alexandre Oliva <oliva at lsd.ic.unicamp.br> writes:
>
> The patch introduces -Mpwd, that causes GCC to output the
> preprocessing directory in the preprocessed output.  This means you
> have to add -Mpwd to BOOT_CFLAGS to get a successful bootstrap, as
> well as to get gdb to find source files in their original location,
> even if using only ccache but using several different yet similar
> source and build trees.  The reasons -Mpwd is not enabled by default
> are backward compatibility (the <directory> directive might be
> unexpected, even though it's in a format that is entirely
> backward-compatible), efficiency and to enable ccache caches to be
> shared by multiple build trees.

(1) I'm with Neil, this should be a separate hook; don't overload
    cb_file_change even more.

(2) I don't think backward compatibility is a major concern here. I
    would rather you used # 1 "/path/to/whatever/" 5 or something like
    that.  Also, I'd rather you put it before the initial LC_ENTER note.
    However, this is nitpicking, I'm not opposed to what you did.  I
    do think there's no reason not to make this unconditional.

(3) Whatever's done, you need to document the new marker in the manual
    section describing the form of preprocessed output.

zw