The recent patch to log changes in postgresql.conf settings dumped core

if the initial value of a string variable was NULL, which is entirely
possible.  Noted while experimenting with custom_variable_classes.

diff --git a/src/backend/utils/misc/guc-file.l b/src/backend/utils/misc/guc-file.l
index 424caea13f5858d06a6249c5f9a6ee320fd106b7..208e54f10c1af24aa77c2a862be383ce703a3fe1 100644 (file)
--- a/src/backend/utils/misc/guc-file.l
+++ b/src/backend/utils/misc/guc-file.l
@@ -4,7 +4,7 @@
  *
  * Copyright (c) 2000-2009, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/utils/misc/guc-file.l,v 1.62 2009/10/03 18:04:57 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/guc-file.l,v 1.63 2009/11/12 18:20:23 tgl Exp $
  */
 
 %{
@@ -316,18 +316,33 @@ ProcessConfigFile(GucContext context)
 
                /* In SIGHUP cases in the postmaster, report changes */
                if (context == PGC_SIGHUP && !IsUnderPostmaster)
-                       pre_value = pstrdup(GetConfigOption(item->name, false));
+               {
+                       const char *preval = GetConfigOption(item->name, false);
+
+                       /* string variables could be NULL; treat that as empty */
+                       if (!preval)
+                               preval = "";
+                       /* must dup, else might have dangling pointer below */
+                       pre_value = pstrdup(preval);
+               }
 
                if (set_config_option(item->name, item->value, context,
                                                                 PGC_S_FILE, GUC_ACTION_SET, true))
                {
                        set_config_sourcefile(item->name, item->filename,
                                                                  item->sourceline);
-                       if (pre_value &&
-                               strcmp(pre_value, GetConfigOption(item->name, false)) != 0)
-                               ereport(elevel,
-                                               (errmsg("parameter \"%s\" changed to \"%s\"",
-                                                               item->name, item->value)));
+
+                       if (pre_value)
+                       {
+                               const char *post_value = GetConfigOption(item->name, false);
+
+                               if (!post_value)
+                                       post_value = "";
+                               if (strcmp(pre_value, post_value) != 0)
+                                       ereport(elevel,
+                                                       (errmsg("parameter \"%s\" changed to \"%s\"",
+                                                                       item->name, item->value)));
+                       }
                }
 
                if (pre_value)