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From: Andrew.Vignaux@comp.vuw.ac.nz (Andrew Vignaux)
Newsgroups: comp.lang.perl
Subject: Re: DBM problems in pl.28
Message-ID: <1990Aug18.024648.19269@comp.vuw.ac.nz>
Date: 18 Aug 90 02:46:48 GMT
References: <1414@esatst.yc.estec.nl>
Sender: news@comp.vuw.ac.nz (News Admin)
Organization: Comp Sci, Victoria University, Wellington, New Zealand.
Lines: 57

In article <1414@esatst.yc.estec.nl>, arne@yc.estec.nl (Arne Lundberg) writes:
|> Since installing patch 28 I have found a problem with dbm files,

I think the problem is in the lazy array creation that went in in
pl.28.  hfetch() only creates the array if the access is an lval and
it hasn't been stored into already.  Unfortunately, dbm files can
already have stuff in them.  The local fix:

      if (!tb->tbl_array) {
! 	if (lval)
  	    Newz(503,tb->tbl_array, tb->tbl_max + 1, HENT*);

to

      if (!tb->tbl_array) {
! 	if (lval || tb->tbl_dbm)
  	    Newz(503,tb->tbl_array, tb->tbl_max + 1, HENT*);

works, but it means that

	dbmopen(FOO,"foo",0666); print defined(%FOO), "\n";

still prints 0.

Here's a completely unofficial patch that (I think) fixes this
problem.  I'm posting this because I can't believe I'm the only one
who depends on dbm files in perl.  I don't want to go back to 18
because of the lack of dbmopen(FOO, "foo", undef) ;-)

*** ./hash.c~	Tue Aug 14 21:17:53 1990
--- ./hash.c	Sat Aug 18 14:22:50 1990
***************
*** 551,556 ****
--- 551,558 ----
      }
      tb->tbl_dbm = dbminit(fname) >= 0;
  #endif
+     if (!tb->tbl_array && tb->tbl_dbm != 0)
+ 	Newz(507,tb->tbl_array, tb->tbl_max + 1, HENT*);
      return tb->tbl_dbm != 0;
  }


This fix also means that

	dbmopen(FOO,"foo",undef); print defined(%FOO), "\n";
and
	dbmopen(BAR,"bar",0666); print defined(%BAR), "\n";

prints 0 if "foo.dir" doesn't exist, or "bar.{dir,pag}" can't be
created.

Both "fixes" pass make test on a MORE/bsd hp300.

Andrew
-- 
Domain address: Andrew.Vignaux@comp.vuw.ac.nz