calling Pa_SelectHostApis now returns an error if it is called while PA is initialized.

include/portaudio.h

@@ -134,7 +134,8 @@ typedef enum PaErrorCode
     paCanNotReadFromAnOutputOnlyStream,
     paCanNotWriteToAnInputOnlyStream,
     paIncompatibleStreamHostApi,
-    paBadBufferPtr
+    paBadBufferPtr,
+    paIsInitialized
 } PaErrorCode;
 
 
@@ -276,8 +277,9 @@ typedef enum PaHostApiTypeId
 
 /** Select host APIs and their initialization order.
 
- The selected host APIs take effect the next time that Pa_Initialize() is
- invoked.
+ This function may only be called prior to calling Pa_Initialize()
+ or after calling Pa_Terminate(). The selected host APIs take effect the
+ next time that Pa_Initialize() is invoked.
 
  @param hostApiTypes An array of host API identifiers belonging to the
  PaHostApiTypeId enumeration.

src/common/pa_front.c

@@ -217,6 +217,11 @@ PaError Pa_SelectHostApis( const PaHostApiTypeId *hostApiTypes, int count )
     PaHostApiTypeId *oldSelectedHostApiTypes = selectedHostApiTypes_;
     PaHostApiTypeId *newSelectedHostApiTypes = NULL;
 
+    if( PA_IS_INITIALISED_ )
+    {
+        return paIsInitialized;
+    }
+
     if( count == 0 )
     {
         /* revert to default state */