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.

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 92073be0ca54b1f3a938f617855992dac43ecb79..72c7377eccab181cdd99ee542552962d322372b5 100644 (file)
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -258,12 +258,13 @@ 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 */