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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