Subject: Re: [PATCH 1/6] lib/cmdline.c: Add backslash support to kernel commandline parsing.

From: Michal Suchánek <[email-masked]>
Date: Mon, 25 Sep 2017 20:39:01 +0200

On Fri, 15 Sep 2017 19:28:56 +0200
Michal Such=C3=A1nek <[email-masked]> wrote:

> On Fri, 15 Sep 2017 18:14:09 +0100
> Al Viro <[email-masked]> wrote:
>=20
> > On Fri, Sep 15, 2017 at 07:02:46PM +0200, Michal Suchanek wrote:
> >  =20
> > >  	for (i =3D 0; args[i]; i++) {
> > > -		if (isspace(args[i]) && !in_quote)
> > > +		if (isspace(args[i]) && !in_quote && !backslash)
> > >  			break;
> > > -		if (equals =3D=3D 0) {
> > > -			if (args[i] =3D=3D '=3D')
> > > -				equals =3D i;
> > > +
> > > +		if ((equals =3D=3D 0) && (args[i] =3D=3D '=3D'))
> > > +			equals =3D i;
> > > +
> > > +		if (!backslash) {
> > > +			if ((args[i] =3D=3D '"') || (args[i] =3D=3D
> > > '\\')) {
> > > +				if (args[i] =3D=3D '"')
> > > +					in_quote =3D !in_quote;
> > > +				if (args[i] =3D=3D '\\')
> > > +					backslash =3D 1;
> > > +
> > > +				memmove(args + 1, args, i);
> > > +				args++;
> > > +				i--;
> > > +			}
> > > +		} else {
> > > +			backslash =3D 0;
> > >  		}
> > > -		if (args[i] =3D=3D '"')
> > > -			in_quote =3D !in_quote;
> > >  	}   =20
> >=20
> > ... and that makes for Unidiomatic Work With Strings Award for this
> > September. Using memmove() for string rewrite is almost always bad
> > taste; in this case it's also (as usual) broken. =20
>=20
> Care to share how it is broken?

Guess not. I will assume it is perfectly fine then. It works perfectly
fine in my testing.

Using memmove for string rewrite is not a matter of taste. It is the
only library function with sane semantics for rewrite of anything. Then
again open-coding it is always an option and maybe in better taste for
some :->

Michal