RangeAnalysis and V3022

Question

Consider the code below:

for (var i = int.MaxValue - 2; i < int.MaxValue; i++)
{
    Console.WriteLine(i);
}
Console.WriteLine();

for (var i = int.MaxValue - 2; i <= int.MaxValue - 1; i++)
{
    Console.WriteLine(i);
}
Console.WriteLine();

for (var i = int.MaxValue - 2; i <= int.MaxValue; i++)
{
    Console.WriteLine(i);
}

The two first loops are expected to print out only the third and second largest integer. The last loop has a bug where i will overflow to int.MinValue and causing an infinite loop.

Running it gives the expected output.

PVS Studio raises three warnings:

V3022 Expression 'i < int.MaxValue' is always true.

V3022 Expression 'i <= int.MaxValue - 1' is always true.

V3022 Expression 'i <= int.MaxValue' is always true.

The bug in the last loop is correctly reported, but the two first warnings are false positives.

Thank you for the feedback. We will look at this false positive soon. — Ilya Ivanov, Jul 10 '17 at 15:08

score 1 · Accepted Answer · answered Jul 14 '17 at 07:59

1

We have fixed this false positive. The fix will be available with the next release.

answered Jul 14 '17 at 07:59

Ilya Ivanov

123
6

1

Just to let you know, this still triggers for `uint i = 0; do { ++i; } while (i != uint.MaxValue);` – Jonas Nyrup Sep 03 '17 at 20:54

RangeAnalysis and V3022

1 Answers1