These macros are in effect at the start of the compilation.
----- ------ --- -- ------ -- --- ----- -- --- ------------

 __G_FLOAT=1  __DECC=1  vms=1  VMS=1  __32BITS=1  __PRAGMA_ENVIRONMENT=1
 __CRTL_VER=80400000  __vms_version="V8.4    "  CC$gfloat=1  __X_FLOAT=1
 vms_version="V8.4    "  __DATE__="Feb 17 2012"  __STDC_VERSION__=199901L
 __DECC_MODE_RELAXED=1  __DECC_VER=70390009  __VMS=1  __ALPHA=1
 VMS_VERSION="V8.4    "  __IEEE_FLOAT=0  __VMS_VERSION="V8.4    "
 __TIME__="05:49:17"  __Alpha_AXP=1  __VMS_VER=80400022
 __BIASED_FLT_ROUNDS=2  __INITIAL_POINTER_SIZE=0  __STDC__=2
 __LANGUAGE_C__=1  __vms=1  __alpha=1  __D_FLOAT=0