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Improve comment about 'if (1)' hack in copy.c macros.

This commit is contained in:
Tom Lane 2009-06-03 15:06:48 +00:00
parent 1a0ebe6152
commit e550763121
1 changed files with 7 additions and 5 deletions
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12
src/backend/commands/copy.c
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@ -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.
*/
/*