Re: Anyone want to help make zsh/db/gdbm work?

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

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On 23 January 2015 at 05:19, Bart Schaefer <schaefer@brasslantern.com>
wrote:
> However, there's still this:
>
> schaefer<518> typeset GDBMDB
> schaefer<519> (){ local GDBMDB; unset GDBMDB; ztie -d db/gdbm -f gdbmdb
GDBMDB }
>  ../../zsh-5.0/Src/params.c:4914: BUG: in restoring scope of special
parameter
> zsh: segmentation fault (core dumped)  Src/zsh

I think this is better, but you may still be able to find ways it
fails.  It's possibly a bit more paranoid than it needs to be;
the PM_REMOVABLE flag is probably the key.

However, in any case I think the way ztie and zuntie work play
fast and loose with parameters.  Try

typeset GDBMB-foo
(){
  local GDBMDB
  unset GDBMDB
  ztie -d db/gdbm -f gdbmdb GDBMDB
  zuntie GDBMDB
}
print $GDBMB

Note there's now a zuntie there.  This still doesn't appear to work.
It now does without the zuntie, though, at least for the most obvious
limited value of "work".

diff --git a/Src/Modules/db_gdbm.c b/Src/Modules/db_gdbm.c
index f079094..d75af98 100644
--- a/Src/Modules/db_gdbm.c
+++ b/Src/Modules/db_gdbm.c
@@ -43,6 +43,9 @@ static char *backtype = "db/gdbm";

 static const struct gsu_scalar gdbm_gsu =
 { gdbmgetfn, gdbmsetfn, gdbmunsetfn };
+/**/
+static const struct gsu_hash gdbm_hash_gsu =
+{ hashgetfn, hashsetfn, gdbmhashunsetfn };

 static struct builtin bintab[] = {
     BUILTIN("ztie", 0, bin_ztie, 1, -1, 0, "d:f:", NULL),
@@ -84,12 +87,14 @@ bin_ztie(char *nam, char **args, Options ops,
UNUSED(int func))
     return 1;
     }

-    if (!(tied_param = createspecialhash(pmname, &getgdbmnode,
&scangdbmkeys, 0))) {
+    if (!(tied_param = createspecialhash(pmname, &getgdbmnode,
&scangdbmkeys,
+                     PM_REMOVABLE))) {
         zwarnnam(nam, "cannot create the requested parameter %s", pmname);
     gdbm_close(dbf);
     return 1;
     }

+    tied_param->gsu.h = &gdbm_hash_gsu;
     tied_param->u.hash->tmpdata = (void *)dbf;

     return 0;
@@ -225,6 +230,25 @@ scangdbmkeys(HashTable ht, ScanFunc func, int flags)

 }

+/**/
+static void
+gdbmhashunsetfn(Param pm, UNUSED(int exp))
+{
+    GDBM_FILE dbf = (GDBM_FILE)(pm->u.hash->tmpdata);
+
+    if (!dbf) /* paranoia */
+    return;
+
+    gdbm_close(dbf);
+    pm->u.hash->tmpdata = NULL;
+
+    /* hash table is now normal, so proceed normally... */
+    pm->node.flags &= ~PM_SPECIAL;
+    pm->gsu.h = &stdhash_gsu;
+    pm->gsu.h->setfn(pm, NULL);
+    pm->node.flags |= PM_UNSET;
+}
+
 #else
 # error no gdbm
 #endif /* have gdbm */