[Mono-bugs] [Bug 331525] New: Int32.TryParse fails to recognize overflows

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=331525

           Summary: Int32.TryParse fails to recognize overflows
           Product: Mono: Class Libraries
           Version: 1.2
          Platform: i686
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: System
        AssignedTo: mono-bugs at ximian.com
        ReportedBy: leonardo+novell at diptongonante.com
         QAContact: mono-bugs at ximian.com
          Found By: ---


Since r82261 in the mcs repository[1], Int32.TryParse incorrectly parses a
number below Int32.MinValue and returns true. See attached test case.

The problem is that the logic implemented in Int32.cs by Miguel in that commit,
although clever, is not guaranteed to behave as expected (i.e. a positive
integer is not always going to become a negative number after overflowing, or
viceversa). When detecting integer overflows in multiplications we're stuck
with having to cast to a larger type (C#'s long in this case) and then make the
check. Not as optimal, but still about 5 times faster than try+catch in my
machine.

Attached is also a patch that includes a possible fix, and adds a few more unit
tests to cover this scenario, and some other cases for the TryParse method
involving hexadecimal numbers.

Thanks.

[1] As a side note, this bug is present in mono 1.2.5


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