I'm working on two extensions, call them "foo" and "bar". bar depends on some of the functions defined in foo. They are both built from a single Makefile, just vanilla PGXS:
MODULES = foo bar
EXTENSION = foo bar
### etc. ###
As bar depends on foo, that's specified in its .control file, and CREATE EXTENSION works just fine with foo created first, then bar.
However, whenever I run one of the UDTs defined in bar, I get this error message:
dev=# SELECT * FROM test1 WHERE (info(bar_dat)).some_prop = 10;
ERROR: could not load library "/vol/data/home/postgres/pg-builds/9.2.4/lib/bar.so": /vol/data/home/postgres/pg-builds/9.2.4/lib/bar.so: undefined symbol: foo_func1