setup.py jumps through hoops to detect gdbm, gdbm_compat, ndbm, and bdb (libdb) build dependencies. I propose to simplify our support matrix and detect all dependencies in configure.ac.

gdbmmodule.c uses gdbm_open() API, which is provided by gdbm.h and libgdbm

dbmmodule.c uses the dbm_open() API, which can be provided by a combination of headers and shared libraries.

- gdbm/ndbm.h with libgdbm_compat
- gdbm-ndbm.h with libgdbm_compat
- ndbm.h with libgdbm_compat
- ndbm.h with libndbm
- db.h with libdb (lib-5.3 for over a decade)

setup.py makes some wrong assumption in regards of libgdbm. The shared library libgdbm does not provide the dbm_open() API on any system I tested. libgdbm_compat is always required. Linking with libgdbm is not needed. libgdbm_compat depends on and wraps libgdbm.

setup.py also performs additional steps to locate old versions of libdb-3.x and libdb-4.x. libdb-5.3 has been around for a decade. Even CentOS 7 and Debian oldoldstable ship with libdb version 5.3 and don't offer libdb version 4. I propose to remove support for libdb 4 and libdb 3.