add vips_thread_shutdown()

You now need to call vips_thread_shutdown() from all threads you create
yourself just before they exit. This gives vips a chance to free any
thread-private memory and to write out profiling data. libvips will
complain noisily if you fail to do this. You can harmlessly call
vips_thread_shutdown() more than once if you wish.

libvips will call vips_thread_shutdown for you automatically for the main
thread (the one that calls vips_shutdown()) and for threads it creates
directly itself.

ChangeLog

@@ -35,6 +35,7 @@
 - redone im_fwfft(), im_invfft(), im_freqflt(), im_disp_ps(), im_fractsurf(),
   im_phasecor() as classes
 - vips_colourspace() allows B_W, GREY16, RGB16 as source / target
+- added vips_thread_shutdown(), thanks Lovell
 
 9/1/14 started 7.36.6
 - fix some clang compiler warnings

libvips/include/vips/vips.h

@@ -169,6 +169,7 @@ extern "C" {
 const char *vips_get_argv0( void );
 void vips_check_init( void );
 void vips_shutdown( void );
+void vips_thread_shutdown( void );
 GOptionGroup *vips_get_option_group( void );
 
 const char *vips_version_string( void );

libvips/iofuncs/buffer.c

@@ -540,7 +540,7 @@ vips_buffer_print( VipsBuffer *buffer )
 static void
 vips__buffer_init_cb( VipsBufferThread *buffer_thread )
 {
-	vips_error_exit( "vips__buffer_shutdown() not called for thread %p",
+	vips_error_exit( "vips_thread_shutdown() not called for thread %p",
 		g_thread_self() ); 
 }
 

libvips/iofuncs/gate.c

@@ -183,14 +183,17 @@ static void
 vips__thread_profile_init_cb( VipsThreadProfile *profile )
 {  
 	/* Threads (including the main thread) must call 
-	 * vips__thread_profile_detach() before exiting. Check that they have.
+	 * vips_thread_shutdown() before exiting. Check that they have.
 	 *
 	 * We can't save automatically, because the shutdown order is
 	 * important. We must free all memory before saving the thread
 	 * profile, for example.
+	 *
+	 * We can't do the freeing in this callback since GPrivate has already
+	 * stopped working. 
 	 */
-	vips_error_exit( "vips__thread_profile_detach() not called "
-		"for thread %p", g_thread_self() ); 
+	vips_error_exit( "vips_thread_shutdown() not called for thread %p", 
+		g_thread_self() ); 
 }
 
 static void
@@ -357,8 +360,10 @@ vips__thread_malloc_free( gint64 size )
 
 	VIPS_DEBUG_MSG_RED( "vips__thread_malloc_free: %zd\n", size ); 
 
+#ifdef VIPS_DEBUG
 	if( !(profile = vips_thread_profile_get()) ) 
 		printf( "argh no block to record free() in!\n" ); 
+#endif /*VIPS_DEBUG*/
 
 	if( (profile = vips_thread_profile_get()) ) { 
 		gint64 time = vips_get_time(); 

libvips/iofuncs/init.c

@@ -369,6 +369,27 @@ vips_leak( void )
 	vips__type_leak();
 }
 
+/**
+ * vips_thread_shutdown: 
+ *
+ * Free any thread-private data and flush any profiling information.
+ *
+ * This function needs to be called when a thread that has been using vips
+ * exits. It is called for you by vips_shutdown() and for any threads created
+ * by vips_g_thread_new(). 
+ *
+ * You will need to call it from threads created in
+ * other ways. If you do not call it, vips will generate an error message.
+ *
+ * May be called many times. 
+ */
+void
+vips_thread_shutdown( void )
+{
+	vips__buffer_shutdown();
+	vips__thread_profile_detach();
+}
+
 /**
  * vips_shutdown:
  *
@@ -396,8 +417,8 @@ vips_shutdown( void )
 		vips__thread_gate_stop( "init: main" ); 
 }
 
-	vips__buffer_shutdown();
-	vips__thread_profile_detach();
+	vips_thread_shutdown();
+
 	vips__thread_profile_stop();
 
 	/* In dev releases, always show leaks. But not more than once, it's

libvips/iofuncs/threadpool.c

@@ -174,11 +174,10 @@ vips_thread_run( gpointer data )
 
 	result = info->func( info->data );
 
-	vips__buffer_shutdown();
-	vips__thread_profile_detach();
-
 	g_free( info ); 
 
+	vips_thread_shutdown();
+
 	return( result ); 
 }