plug a memory leak by CALLBACK,

deleting locally malloced memory

src/xspice/icm/analog/pwl/cfunc.mod

@@ -224,6 +224,25 @@ NON-STANDARD FEATURES
 
 ==============================================================================*/
 
+static void
+cm_pwl_callback(ARGS, Mif_Callback_Reason_t reason)
+{
+    switch (reason) {
+        case MIF_CB_DESTROY: {
+            double *last_x_value = STATIC_VAR (last_x_value);
+            double *x = STATIC_VAR (x);            
+            double *y = STATIC_VAR (y);            
+            free(last_x_value);
+            free(x);
+            free(y);
+            STATIC_VAR (last_x_value) = NULL;
+            STATIC_VAR (x) = NULL;
+            STATIC_VAR (y) = NULL;            
+            break;
+        }
+    }
+}
+
 /*=== CM_PWL ROUTINE ================*/
 
 void cm_pwl(ARGS)  /* structure holding parms, 
@@ -250,7 +269,9 @@ void cm_pwl(ARGS)  /* structure holding parms,
     double test;            /* temp storage variable for limit testing */
 
     Mif_Complex_t ac_gain;
-                                           
+
+    CALLBACK = cm_pwl_callback;
+
     char *allocation_error="\n***ERROR***\nPWL: Allocation calloc failed!\n";
     char *limit_error="\n***ERROR***\nPWL: Violation of 50% rule in breakpoints!\n";