is libpq thread safe without configure enable_thread_safety=yes

I want to use the libpq in a multithreaded process. I intend to use two
different connections for two different threads. The requests and results
for each connection will be handled completely by each thread independently.
I tried to set enable_thread_safety and enable_thread_safety_force to yes.
However, the compile fails because of references to pthread routines which are not
supported by my os. Specifically:

../../../src/interfaces/libpq/libpq.so: undefined reference to `pthread_sigmask'
../../../src/interfaces/libpq/libpq.so: undefined reference to `pthread_mutex_unlock'
../../../src/interfaces/libpq/libpq.so: undefined reference to `pthread_mutex_lock'
../../../src/interfaces/libpq/libpq.so: undefined reference to `sigwait'

I can change the code to fix this, but I wondering if based on my application it is okay
to just configure without setting enable_thread_safety.

Thanks for any help.
Andrew

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