oleaut32: Fix the overflow check in VarNumFromParseNum.

dlls/oleaut32/tests/vartype.c

@@ -2592,7 +2592,9 @@ static void test_VarUI8FromStr(void)
   CONVERT_STR(VarUI8FromStr,"0",0);                     EXPECTI8(0);
   CONVERT_STR(VarUI8FromStr,"-1",0);                    EXPECT_OVERFLOW;
   CONVERT_STR(VarUI8FromStr,"2147483647",0);            EXPECTI8(2147483647);
-  CONVERT_STR(VarUI8FromStr,"18446744073709551615",0);  todo_wine EXPECTI864(0xFFFFFFFF,0xFFFFFFFF);
+  CONVERT_STR(VarUI8FromStr,"18446744073709551614",0);  EXPECTI864(0xFFFFFFFF,0xFFFFFFFE);
+  CONVERT_STR(VarUI8FromStr,"18446744073709551615",0);  EXPECTI864(0xFFFFFFFF,0xFFFFFFFF);
+  CONVERT_STR(VarUI8FromStr,"18446744073709551616",0);  EXPECT_OVERFLOW;
 
   CONVERT_STR(VarUI8FromStr,"-1.5",LOCALE_NOUSEROVERRIDE); EXPECT_OVERFLOW;
   CONVERT_STR(VarUI8FromStr,"-0.6",LOCALE_NOUSEROVERRIDE); EXPECT_OVERFLOW;

dlls/oleaut32/variant.c

@@ -2186,7 +2186,7 @@ HRESULT WINAPI VarNumFromParseNum(NUMPARSE *pNumprs, BYTE *rgbDig,
     /* Convert the integer part of the number into a UI8 */
     for (i = 0; i < wholeNumberDigits; i++)
     {
-      if (ul64 > (UI8_MAX / 10 - rgbDig[i]))
+      if (ul64 > UI8_MAX / 10 || (ul64 == UI8_MAX / 10 && rgbDig[i] > UI8_MAX % 10))
       {
         TRACE("Overflow multiplying digits\n");
         bOverflow = TRUE;