I recommend against using ctypes. The find_library function does not take distutils / setuptools options and flags into account. OpenLDAP 2.6 finally ships pkg-config files, so you could use pkg-config on Unix-like systems and figure out a fallback for OpenLDAP 2.4 and for Windows.

Thanks for pointing me to setuptools API, didn't know these things were available, still nothing there I can find for examining pkg-config files nor tools to examine ldap.h to get the library version/feature flags so that doesn't get us all the way.

I could tweak the patch as you suggest below (using cmdclass) to find the right library path, but will have to dlopen it with ctypes anyway. Feel free to tweak the PR or suggest an alternative approach.

I like the OPENLDAP_THREAD_SAFE check. Should we check the flags in the module initializer of the C extension instead?

Alternatively, we could just say we assume libldap is thread safe (switching to setting LIBLDAP_R at load time) and require that people building on distros where libldap and libldap_r do not point to the same library (if there are any left) choose to link to libldap_r by hand.

setuptools has no code to run pkg-config. You need to role your own code, e.g. run pkg-config --libs, shlex the output, and extend extra_linker_args. Do the same for cflags and extra compiler args.

You could use self.compiler.preprocess to run the pre-processor with a feature check file like this and check the exit code:

#include <ldap.h>

#ifndef LDAP_API_FEATURE_X_OPENLDAP_THREAD_SAFE
#errror "no thread safe"
#endif

Or keep it really simple:

• check for ldap_r, if present use ldap_r
• otherwise use ldap
• add a check for thread safe libldap to _ldap extension module and fail to compile / load when a non-reentrant LDAP lib is present.

Just been testing find_library_file() and if passed empty library_dirs (the default in our case), it will always return None anyway, so that's no use whatsoever for us.

Just been testing find_library_file() and if passed empty library_dirs (the default in our case), it will always return None anyway, so that's no use whatsoever for us.

As shown in my initial example, you have to pass a combination of compiler and extension library dirs to the function.

library_dirs = self.compiler.library_dirs + ext.library_dirs

As shown in my initial example, you have to pass a combination of compiler and extension library dirs to the function.

Which is what I tested with. Anyway, I did away with all that and just moved to the runtime check.

@tiran any feedback on the comments?