From a5cf8700b6b69d5b9a389a98bfa2abbcd76388f7 Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <gray@gnu.org>
Date: Thu, 12 Aug 2021 14:34:10 +0300
Subject: Fix NULL dereference in gdbmshell.  Undefine "fd" upon closing the
 database.

---
 doc/gdbm.texi   | 30 ++++++++++++++++++++++++------
 src/gdbmshell.c |  1 +
 src/var.c       | 10 ++++++++++
 3 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/doc/gdbm.texi b/doc/gdbm.texi
index a989e48..9c54f74 100644
--- a/doc/gdbm.texi
+++ b/doc/gdbm.texi
@@ -3487,25 +3487,43 @@ See also @code{first}, above.
 @end deffn
 
 @deffn {command verb} open @var{filename}
-Open the database file @var{filename}.  If successful, any previously
-open database is closed.  Otherwise, if the operation fails, the
-currently opened database remains unchanged.
+@deffnx {command verb} open
+Open the database file @var{filename}.  If used without arguments, the
+database name is taken from the variable @code{filename}.
+
+If successful, any previously open database is closed and the
+@code{filename} variable is updated.  Otherwise, if the operation
+fails, the currently opened database remains unchanged.
 
 This command takes additional information from the following
 variables:
 
-@table @samp
+@table @code
+@item filename
+Name of the database to open, if no argument is given.
+
+@item fd
+File descriptor to use.  If set, this must be an open file descriptor
+referring to a valid database file.  The database will be opened using
+@code{gdbm_fd_open} (@pxref{gdbm_fd_open}).  The file descriptor will
+be closed upon closing the database.
+
+@item filemode
+Specifies the permissions to use in case a new file is created.
+
 @item open
 The database access mode.  @xref{openvar,, The @var{open} variable},
 for a list of its values.
+
 @item lock
 Whether or not to lock the database.  Default is @code{on}.
+
 @item mmap
 Use the memory mapping.  Default is @code{on}.
+
 @item sync
 Synchronize after each write.  Default is @code{off}.
-@item filemode
-Specifies the permissions to use in case a new file is created.
+
 @end table
 
 @xref{open parameters}, for a detailed description of these variables.
diff --git a/src/gdbmshell.c b/src/gdbmshell.c
index 8a2b07b..62402e1 100644
--- a/src/gdbmshell.c
+++ b/src/gdbmshell.c
@@ -67,6 +67,7 @@ closedb (void)
 
   datum_free (&key_data);
   datum_free (&return_data);
+  variable_unset ("fd");
 }
 
 static int
diff --git a/src/var.c b/src/var.c
index 2772eb1..7b583e2 100644
--- a/src/var.c
+++ b/src/var.c
@@ -567,6 +567,8 @@ open_typeconv (struct variable *var, int type, void **retptr)
 static int
 format_sethook (struct variable *var, union value *v)
 {
+  if (!v)
+    return VAR_OK;
   return _gdbm_str2fmt (v->string) == -1 ? VAR_ERR_BADVALUE : VAR_OK;
 }
 
@@ -584,6 +586,8 @@ format_typeconv (struct variable *var, int type, void **retptr)
 static int
 fd_sethook (struct variable *var, union value *v)
 {
+  if (!v)
+    return VAR_OK;
   if (v->num < 0)
     return VAR_ERR_BADVALUE;
   return VAR_OK;
@@ -592,6 +596,8 @@ fd_sethook (struct variable *var, union value *v)
 static int
 cachesize_sethook (struct variable *var, union value *v)
 {
+  if (!v)
+    return VAR_OK;
   if (v->num < 0)
     return VAR_ERR_BADVALUE;
   return gdbmshell_setopt ("GDBM_SETCACHESIZE", GDBM_SETCACHESIZE, v->num) == 0
@@ -601,6 +607,8 @@ cachesize_sethook (struct variable *var, union value *v)
 static int
 centfree_sethook (struct variable *var, union value *v)
 {
+  if (!v)
+    return VAR_OK;
   return gdbmshell_setopt ("GDBM_SETCENTFREE", GDBM_SETCENTFREE, v->bool) == 0
          ? VAR_OK : VAR_ERR_BADVALUE;
 }
@@ -608,6 +616,8 @@ centfree_sethook (struct variable *var, union value *v)
 static int
 coalesce_sethook (struct variable *var, union value *v)
 {
+  if (!v)
+    return VAR_OK;
   return gdbmshell_setopt ("GDBM_SETCOALESCEBLKS", GDBM_SETCOALESCEBLKS, v->bool) == 0
          ? VAR_OK : VAR_ERR_BADVALUE;
 }
-- 
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