Re: Fix makedepend depmode to cope with VPATH builds

[Ralf Wildenhues]

* Stefano Lattarini wrote on Sat, Apr 09, 2011 at 12:29:43PM CEST:
> On Saturday 09 April 2011, Ralf Wildenhues wrote:
> > I guess then I don't understand your observation then.  Your observation
> > tells me that object file names of the form foo^bar.o and foo$baz.o are
> > not problematic.
> >
> No.  It just tells that sed regular expressions like [ab.^$0-9] are not
> problematic, because `.' and `$' are *not* recognized as metacharacters
> in *bracket expression*, and `^' is recognized as a metacharacter in a
> bracket expression only when used as *first* character there.  Which
> simply means that your original command:
>   sed_object_re=`echo $object | sed 's/[].[^$\\*|]/\\\\&/g'`
> was fully correct, and didn't lack any required escaping (while, on the
> first impression, I had *erronously* thought it did).

OK.

But independently of bracket expressions, Posix also specifies that ^
and $ are not special when they are not first or last characters in a
regex, respectively.  This is what makes object file names of the form
foo^bar.o and foo$bar.o acceptable.  Even ^foo.o, since our sed regex
does not start with $object.

> But re-reading what I wrote in my first reply, I must admit it sounded
> like I was adding something new to the discussion, while in fact I was
> just saying "hey, at first I wasn't sure that this change of yours was
> correct, but by reading the standards/manuals more carefully, I realized
> you are indeed completely right".  Miscommunication on my part -- sorry
> for the noise and the time I made us loose.

Naah, it's better to be picky and find out we're safe after all, than
the other way round.

> > Remember the input
> > file only contains lines of the form
> >   $object: header header...
> >   $object: header \
> >    header header...
> > While somebody might arguably name their header foo.o, I do think they
> > deserve what they get.
> >
> Agreed.  Especially because, to cause a spurious match, they would have to
> *also* have a `:' character in the header name, i.e., have an header named
> like "foo.o:bar.h" or "foo.obj:bar.h" -- in which case they probably do
> deserve to suffer a bit.

Right.

> > > > @@ -503,7 +503,8 @@ makedepend)
> > > >    touch "$tmpdepfile"
> > > >    ${MAKEDEPEND-makedepend} -o"$obj_suffix" -f"$tmpdepfile" "$@"
> > > >    rm -f "$depfile"
> > > > -  cat < "$tmpdepfile" > "$depfile"
> > > > +  # makedepend may prepend the VPATH from the source file name to the 
> > > > object.
> > > >
> > > I'd add a comment here telling why there's no need to escape $object for 
> > > the
> > > sed commmand just below.
> > 
> > I will, after I've understood your remaining comments.
> >
> Hope this reply is clearer than the previous ones.

Yup.  I'm adding the following.

Thanks,
Ralf

    Clarify regex code in depcomp.
    
    * lib/depcomp: Add comment why we don't need regex-escaping here.
    Suggested by Stefano Lattarini.

diff --git a/lib/depcomp b/lib/depcomp
index ce9419c..8097c19 100755
--- a/lib/depcomp
+++ b/lib/depcomp
@@ -1,7 +1,7 @@
 #! /bin/sh
 # depcomp - compile a program generating dependencies as side-effects
 
-scriptversion=2011-04-08-18; # UTC
+scriptversion=2011-04-09-11; # UTC
 
 # Copyright (C) 1999, 2000, 2003, 2004, 2005, 2006, 2007, 2009, 2011,
 # Free Software Foundation, Inc.
@@ -504,6 +504,7 @@ makedepend)
   ${MAKEDEPEND-makedepend} -o"$obj_suffix" -f"$tmpdepfile" "$@"
   rm -f "$depfile"
   # makedepend may prepend the VPATH from the source file name to the object.
+  # No need to regex-escape $object, excess matching of '.' is harmless.
   sed "s|^.*\($object *:\)|\1|" "$tmpdepfile" > "$depfile"
   sed '1,2d' "$tmpdepfile" | tr ' ' '
 ' | \