Repair an error introduced by log_line_prefix patch: it is not acceptable

to assume that the string pointer passed to set_ps_display is good forever.
There's no need to anyway since ps_status.c itself saves the string, and
we already had an API (get_ps_display) to return it.
I believe this explains Jim Nasby's report of intermittent crashes in
elog.c when %i format code is in use in log_line_prefix.
While at it, repair a previously unnoticed problem: on some platforms such as
Darwin, the string returned by get_ps_display was blank-padded to the maximum
length, meaning that lock.c's attempt to append " waiting" to it never worked.

2 files changed, 32 insertions, 12 deletions

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 64403ce9b18..44ebac245c9 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -42,7 +42,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/error/elog.c,v 1.166 2005/11/03 17:11:39 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/error/elog.c,v 1.167 2005/11/05 03:04:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -67,6 +67,7 @@
 #include "tcop/tcopprot.h"
 #include "utils/memutils.h"
 #include "utils/guc.h"
+#include "utils/ps_status.h"
 
 
 /* Global variables */
@@ -1484,19 +1485,26 @@ log_line_prefix(StringInfo buf)
 				break;
 			case 'i':
 				if (MyProcPort)
-					appendStringInfo(buf, "%s", MyProcPort->commandTag);
+				{
+					const char *psdisp;
+					int		displen;
+
+					psdisp = get_ps_display(&displen);
+					appendStringInfo(buf, "%.*s", displen, psdisp);
+				}
 				break;
 			case 'r':
-				if (MyProcPort)
+				if (MyProcPort && MyProcPort->remote_host)
 				{
 					appendStringInfo(buf, "%s", MyProcPort->remote_host);
-					if (strlen(MyProcPort->remote_port) > 0)
+					if (MyProcPort->remote_port &&
+						MyProcPort->remote_port[0] != '\0')
 						appendStringInfo(buf, "(%s)",
 										 MyProcPort->remote_port);
 				}
 				break;
 			case 'h':
-				if (MyProcPort)
+				if (MyProcPort && MyProcPort->remote_host)
 					appendStringInfo(buf, "%s", MyProcPort->remote_host);
 				break;
 			case 'q':
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index af1421cd2f6..878ff81e241 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -5,7 +5,7 @@
  * to contain some useful information. Mechanism differs wildly across
  * platforms.
  *
- * $PostgreSQL: pgsql/src/backend/utils/misc/ps_status.c,v 1.25 2005/10/15 02:49:36 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/ps_status.c,v 1.26 2005/11/05 03:04:52 tgl Exp $
  *
  * Copyright (c) 2000-2005, PostgreSQL Global Development Group
  * various details abducted from various places
@@ -307,10 +307,6 @@ init_ps_display(const char *username, const char *dbname,
 void
 set_ps_display(const char *activity)
 {
-	/* save tag for possible use by elog.c */
-	if (MyProcPort)
-		MyProcPort->commandTag = activity;
-
 #ifndef PS_USE_NONE
 	/* no ps display for stand-alone backend */
 	if (!IsUnderPostmaster)
@@ -365,15 +361,31 @@ set_ps_display(const char *activity)
 
 /*
  * Returns what's currently in the ps display, in case someone needs
- * it.	Note that only the activity part is returned.
+ * it.	Note that only the activity part is returned.  On some platforms
+ * the string will not be null-terminated, so return the effective
+ * length into *displen.
  */
 const char *
-get_ps_display(void)
+get_ps_display(int *displen)
 {
 #ifdef PS_USE_CLOBBER_ARGV
+	size_t		offset;
+
 	/* If ps_buffer is a pointer, it might still be null */
 	if (!ps_buffer)
+	{
+		*displen = 0;
 		return "";
+	}
+
+	/* Remove any trailing spaces to offset the effect of PS_PADDING */
+	offset = ps_buffer_size;
+	while (offset > ps_buffer_fixed_size && ps_buffer[offset-1] == PS_PADDING)
+		offset--;
+
+	*displen = offset - ps_buffer_fixed_size;
+#else
+	*displen = strlen(ps_buffer + ps_buffer_fixed_size);
 #endif
 
 	return ps_buffer + ps_buffer_fixed_size;