Re: [PATCH 2/4] Mechanical conversion to use prefixcmp()

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > Ha, I did it by
> >
> > $ perl -pi.bup -e \
> >  's/strncmp\( *("[^"]*"), *([^"]*), *[0-9]* *\)/prefixcmp\($2, $1\)/g' \
> >  $(git ls-files)
> >
> > and
> >
> > $ perl -pi.bup -e \
> >  's/strncmp\( *([^"]*), *("[^"]*"), *[0-9]* *\)/prefixcmp\($1, $2\)/g' \
> >  $(git-ls-files)
> >
> > Of course, I missed the two ,ofs ones, but a git grep -n strncmp brought 
> > these up.
> 
> I think you totally missed my point.  I wanted to make sure that
> things like these do not go unnoticed:
> 
>         if (!strncmp(arg, "--foo==", 6))
> 	if (strncmp(line, "foo\nbar", 8))
> 
> Both are probably incorrectly written code in the original, but
> probably would _happen_ to be working (for a certain definition
> of "working" -- the former probably wanted to make sure the
> parameter is of form "--foo=something", and the latter wanted to
> check the line has the 7 bytes terminated with NUL).  But your
> conversion would make them actually start behaving incorrectly.
> 
> And the worst part of this is that the change that caused to
> expose these bugs would be literally _buried_ in 1800 lines of
> "mechanical conversion" patch which is mind-numbing to audit.
> 
> That's why you are better off writing mechanical conversion
> script in stricter than seemingly necessary to catch only the
> safe conversion target, while accepting false negatives.