From f2717c79eeecaf5997016d52fd81881301dcfc5e Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 10 Sep 2016 17:54:23 -0400
Subject: [PATCH] Improve unreachability recognition in elog() macro.
Some experimentation with an older version of gcc showed that it is able
to determine whether "if (elevel_ >= ERROR)" is compile-time constant
if elevel_ is declared "const", but otherwise not so much. We had
accounted for that in ereport() but were too miserly with braces to
make it so in elog(). I don't know how many currently-interesting
compilers have the same quirk, but in case it will save some code
space, let's make sure that elog() is on the same footing as ereport()
for this purpose.
Back-patch to 9.3 where we introduced pg_unreachable() calls into
elog/ereport.
---
src/include/utils/elog.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f4ff03ec8a1..70dc365465c 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -206,12 +206,13 @@ extern int getinternalerrposition(void);
#else /* !HAVE__BUILTIN_CONSTANT_P */
#define elog(elevel, ...) \
do { \
- int elevel_; \
elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
- elevel_ = (elevel); \
- elog_finish(elevel_, __VA_ARGS__); \
- if (elevel_ >= ERROR) \
- pg_unreachable(); \
+ { \
+ const int elevel_ = (elevel); \
+ elog_finish(elevel_, __VA_ARGS__); \
+ if (elevel_ >= ERROR) \
+ pg_unreachable(); \
+ } \
} while(0)
#endif /* HAVE__BUILTIN_CONSTANT_P */
#else /* !HAVE__VA_ARGS */
--
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