scanf: when an ordinary character cannot match due to EOF, flag an input failure.

This may cause scanf to return EOF, if no conversions have been done.

This seems to be the intent of the C standards, although the wording could be clearer. It is also consistent with all the other implementations I tested.

stdio.asm

@@ -5500,7 +5500,10 @@ ps5	stx	ch	make sure the char matches the format
 	jsl	~getchar
 	cmp	ch
 	beq	ps1
-	jsl	~putback	put the character back
+	cmp	#EOF	check for EOF
+	bne	ps6
+	sta	~eofFound
+ps6	jsl	~putback	put the character back
 ;
 ;  Remove the parameters for remaining conversion specifications
 ;