Some modern distros (Mageia, Mandriva) use -no-undefined as a default linker flag for building software. However, undefined symbols are OK if the binary being linked is a plugin. To detect plugins, build system looks for presence of "-module" libtool flag in makefiles.
There are two libraries in Pigeonhole that couldn't be linked with -no-undefined:
src/lib-sieve/plugins/mailbox/libsieve_ext_mailbox.la src/lib-sieve/libdovecot-sieve.la
These modules do contain undefined symbols, but they are not linked against library that provides them. It would be good if corresponding makefiles contained "-module" flags, so that build system could selectively turn off that -no-undefined linker flag. Please see proposed patch (attached).
Thanks, Dimitri Mageia Linux packager