From e5507631219392d08f327194c840e042e3577fc5 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 3 Jun 2009 15:06:48 +0000
Subject: [PATCH] Improve comment about 'if (1)' hack in copy.c macros.
---
src/backend/commands/copy.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 4f4b8474b09..7840e7b52cf 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.310 2009/06/03 14:48:33 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.311 2009/06/03 15:06:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -175,11 +175,13 @@ typedef struct
/*
* These macros centralize code used to process line_buf and raw_buf buffers.
* They are macros because they often do continue/break control and to avoid
- * function call overhead in tight COPY loops. "((void) 0)" is used to silence
- * compiler warnings.
+ * function call overhead in tight COPY loops.
*
- * We must use "if (1)" because "do {} while(0)" overrides the continue/break
- * processing. See http://www.cit.gu.edu.au/~anthony/info/C/C.macros.
+ * We must use "if (1)" because the usual "do {...} while(0)" wrapper would
+ * prevent the continue/break processing from working. We end the "if (1)"
+ * with "else ((void) 0)" to ensure the "if" does not unintentionally match
+ * any "else" in the calling code, and to avoid any compiler warnings about
+ * empty statements. See http://www.cit.gu.edu.au/~anthony/info/C/C.macros.
*/
/*
--
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