Issue #18256: Compilation fix for recent AIX releases. Patch by David Edelsohn.

Misc/ACKS

@@ -334,6 +334,7 @@ Maxim Dzumanenko
 Walter Dörwald
 Hans Eckardt
 Rodolpho Eckhardt
+David Edelsohn
 John Edmonds
 Grant Edwards
 John Ehresman

Misc/NEWS

@@ -537,6 +537,9 @@ IDLE
 Build
 -----
 
+- Issue #18256: Compilation fix for recent AIX releases.  Patch by
+  David Edelsohn.
+
 - Issue #17547: In configure, explicitly pass -Wformat for the benefit for GCC
   4.8.
 

Python/thread_pthread.h

@@ -170,6 +170,7 @@ static void
 PyThread__init_thread(void)
 {
 #if defined(_AIX) && defined(__GNUC__)
+    extern void pthread_init(void);
     pthread_init();
 #endif
 }
@@ -444,6 +445,7 @@ PyThread_free_lock(PyThread_type_lock lock)
     pthread_lock *thelock = (pthread_lock *)lock;
     int status, error = 0;
 
+    (void) error; /* silence unused-but-set-variable warning */
     dprintf(("PyThread_free_lock(%p) called\n", lock));
 
     /* some pthread-like implementations tie the mutex to the cond
@@ -530,6 +532,7 @@ PyThread_release_lock(PyThread_type_lock lock)
     pthread_lock *thelock = (pthread_lock *)lock;
     int status, error = 0;
 
+    (void) error; /* silence unused-but-set-variable warning */
     dprintf(("PyThread_release_lock(%p) called\n", lock));
 
     status = pthread_mutex_lock( &thelock->mut );