Add printf() comment, return length of printed message

tests.asm

@@ -83,6 +83,7 @@ section	.rodata
 	msgPrintf	db	NL,"# printf()",EOS
 	msgPrintf1	db	"TEST printf()",NL,EOS
 	msgPrintf2	db	"TEST printf(testStr, tS1, tS2, tS3, tS4, tS5, tS6, tS7, tS8, num1, tS9)",NL,EOS
+	msgPrintf2b	db	"Return value: %d",NL,EOS
 	; min() / minu()
 	msgMin		db	NL,"# min() / minu()",EOS
 	msgMin1		db	"TEST min(num1, num2): %d",NL,EOS
@@ -239,6 +240,9 @@ main:
 	push	tS6
 	call	printf
 	add	rsp, 40 ;cleanup stack, 8*5
+	mov	rsi, rax
+	lea	rdi, [msgPrintf2b]
+	call	printf
 %ENDIF
 %IF TEST_min
 	lea	rdi, [rel msgMin]