bin/59883: divert cannot be renamed in FreeBSD m4 [with patch]

[Craig Boston]

The following reply was made to PR bin/59883; it has been noted by GNATS.

From: Craig Boston <craig at olyun.gank.org>
To: freebsd-gnats-submit at FreeBSD.org, bremner at unb.ca
Cc:  
Subject: Re: bin/59883: divert cannot be renamed in FreeBSD m4 [with patch]
Date: Tue, 27 Apr 2004 23:50:34 -0500

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 Hi,
 
 I've recently run into the same problem with our m4 -- defn() appears to not 
 work correctly with builtins, so they cannot be copied/renamed at all.
 
 The problem seems to be the result of a commit from about 2 years (!) ago.  
 Guess nobody uses BSD m4 very much :)
 
 http://www.freebsd.org/cgi/cvsweb.cgi/src/usr.bin/m4/main.c?rev=1.14&content-type=text/x-cvsweb-markup
 
 	p->defn = null;
 
 was changed to
 
 	p->defn = xstrdup(null);
 
 as part of a GCC3 const/WARNS sweep.  null is apparently a pointer to a 
 somewhat "magic" empty string.  The problem happens in dodefn() in eval.c 
 when this is checked:
 
 	if (p->defn != null) {
 		[ do stuff for macros ]
 	} else ... {
 		[ do stuff for builtins ]
 	}
 
 p->defn is no longer == to null for builtins, but rather a copy of it.  I 
 changed it to instead check p->type to see if it's a macro or not and that 
 seems to fix it.  Also checked the OpenBSD CVS and it looks like they fixed 
 the problem there with a very similar (though more extensive) approach.  A 
 quick grep/once-over of the code didn't turn up any more (ab)use of pointers 
 to "null" that would be affected by this.
 
 Patch is both inline (tabs mangled I'm sure) and attached -- I don't remember 
 if gnats accepts MIME attachments :-/
 
 --- eval.c.orig	Tue Apr 27 23:33:03 2004
 +++ eval.c	Tue Apr 27 23:33:57 2004
 @@ -617,7 +617,7 @@
  	const char *real;
  
  	if ((p = lookup(name)) != nil) {
 -		if (p->defn != null) {
 +		if ((p->type & TYPEMASK) == MACRTYPE) {
  			pbstr(rquote);
  			pbstr(p->defn);
  			pbstr(lquote);
 
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   name="bsd.m4.defn.patch"
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 	filename="bsd.m4.defn.patch"
 
 --- eval.c.orig	Tue Apr 27 23:33:03 2004
 +++ eval.c	Tue Apr 27 23:33:57 2004
 @@ -617,7 +617,7 @@
  	const char *real;
  
  	if ((p = lookup(name)) != nil) {
 -		if (p->defn != null) {
 +		if ((p->type & TYPEMASK) == MACRTYPE) {
  			pbstr(rquote);
  			pbstr(p->defn);
  			pbstr(lquote);
 
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