So here's a "fun" thing I discovered while updating python: % pkg-config libffi --cflags-only-I -I/opt/local/include
% env CPATH=/opt/local/include pkg-config libffi --cflags-only-I (Second command prints a blank line.) This appears to be a deliberate behaviour designed to avoid including paths that will be searched by the compiler by default. And to be fair, it's probably OK a lot of the time. Python, however, uses the output to determine whether it's using the system libffi on macOS. There is another variable PKG_CONFIG_ALLOW_SYSTEM_CFLAGS which prevents the affected paths from being removed from the output. I'm not sure whether it would be a good idea to set that all the time in base. Hopefully this information will help someone else avoid being driven slightly crazy when pkg-config behaves differently in a port's configure script than it does in a shell. - Josh
