In config/c-compiler.m4 I read
if test "$ac_env_CFLAGS_set" != set; then
CFLAGS="$CFLAGS $pgac_cv_prog_cc_no_strict_aliasing"
fi
This means that a configure operation as innocuous-looking as
CFLAGS="-O3" ./configure
will break the build on gcc >= 3.3 because it will fail to supply
-fno-strict-aliasing. I claim this is a lousy idea. We should drop
the if-test and always add -fno-strict-aliasing if the compiler
will take it. People who *really* know what they are doing can
experiment with removing the switch from Makefile.global after
configure, but I don't think it should be quite this easy to lose it.
regards, tom lane