Location to specify C compiler option in C extension

Hi,

I’m writing a C extension and have successfully based my Makefile on existing templates. This conveniently hides the details of the full Makefile provided by "pg_config --pgxs”. Which variable would be the appropriate one to specify the ‘-std=c99’ compiler flag? I’ve tried many and still get warnings that this flag should suppress (specifically, "ISO C90 forbids mixed declarations and code”). These are the variables I currently define:

EXTENSION
DATA
PGFILEDESC
MODULE_big
PG_CPPFLAGS (this one seemed like the right place)
SHLIB_LINK
OBJS
PG_CONFIG
PGXS

A workaround has been:

OBJS = file1.o file2.o CPPFLAGS+=-Wdeclaration-after-statement

but it’s not exactly the same thing.

Thanks,
Demitri