Hi Tom,
PG_CPPFLAGS ought to work. One point is that you need to set that before
including pgxs.mk; maybe it's an ordering problem?
On closer inspection, it was working, but the pg Makefile was specifically including “-Wdeclaration-after-statement” which I think was overriding the ‘-std=c99’ part. The line below fixed the problem.
PG_CPPFLAGS += -std=c99 -Wno-declaration-after-statement
Thanks, sorry for the noise.
Demitri