fix O2 optimization distorsions

Makefile

@@ -1,5 +1,5 @@
 PKGFLAGS:=$(shell pkg-config --cflags --libs openssl ao)
-CFLAGS:=-O0
+CFLAGS:=-O2
 LDFLAGS:=-lm -lpthread
 PAUFLAGS:=-lportaudio
 

hairtunes.c

@@ -628,6 +628,8 @@ int stuff_buffer(double playback_rate, short *inptr, short *outptr) {
             *outptr++ = dithered_vol(*inptr++);
         }
     }
+
+    return stuffsamp;
 }
 
 void *audio_thread_func(void *arg) {