Versioning is for libraries. Modules are not libraries; no code is linked
against them.
Libtool makes sure the modules can be opened by dlopen(). That is already
true for ELF format, but other file formats may need special processing.
AM_CPPFLAGS is a documented Automake variable for C preprocessor flags
that should not be overridden when compiling the package.
There is no need to have two additional variables that are ultimately
merged into AM_CPPFLAGS.
Their names are also confusing. EXTDA_DIST is a documented Automake
variable. Everything else that starts with "EXTRA" is not.
libdir is for shared and static libraries. Some xrdp libraries are loaded
dynamically from a non-standard directory, so they are used like modules.
Having separate libdir and moduledir would eventually allow to separate
dynamically loaded modules from shared libraries.
AM_CPPFLAGS is for flags passed to the preprocessor, such as defines and
includes. AM_CFLAGS is for flags affecting the compiler, such as debug
and optimization settings.
INCLUDES is an obsolete name. Users can pass INCLUDES and break
compilation. AM_CPPFLAGS is more explicit that the flags come from
Automake and should not be overridden.
matt335672