--- previous/src/cpu/cpummu.c	2018/04/24 19:27:55	1.1.1.2
+++ previous/src/cpu/cpummu.c	2018/04/24 19:29:03	1.1.1.3
@@ -860,19 +860,20 @@ static int s_try_stack_size=0;
 static jmp_buf s_try_stack[MAX_TRY_STACK];
 jmp_buf* __poptry(void) {
 	if (s_try_stack_size>0) {
-			s_try_stack_size--;
-			if (s_try_stack_size>0)
-				memcpy(&__exbuf,&s_try_stack[s_try_stack_size-1],sizeof(jmp_buf));
-			// fprintf(stderr,"pop jmpbuf=%08x\n",s_try_stack[s_try_stack_size][0]);
-			return &s_try_stack[s_try_stack_size-1];
-		}
+        s_try_stack_size--;
+        if (s_try_stack_size == 0)
+            return NULL;
+        memcpy(&__exbuf,&s_try_stack[s_try_stack_size-1],sizeof(jmp_buf));
+        // fprintf(stderr,"pop jmpbuf=%08x\n",s_try_stack[s_try_stack_size][0]);
+        return &s_try_stack[s_try_stack_size-1];
+    }
 	else {
 		fprintf(stderr,"try stack underflow...\n");
 	    // return (NULL);
 		abort();
 	}
 }
-void __pushtry(jmp_buf* j) { 
+void __pushtry(jmp_buf* j) {
 	if (s_try_stack_size<MAX_TRY_STACK) {
 		// fprintf(stderr,"push jmpbuf=%08x\n",(*j)[0]);
 		memcpy(&s_try_stack[s_try_stack_size],j,sizeof(jmp_buf));