Author: Dann Corbit
Date: 15:33:12 04/09/04
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On April 09, 2004 at 18:04:10, Russell Reagan wrote: >I'm posting this here because I know that some of the programmers here use MSVC >.NET 2003, and in hopes that Eugene will read this :) > >Today I had a problem with a program I was writing, and I came across what I >believe is an optimization bug. I wrote this little program to reproduce the >bug. If I compile with optimizations set to "Disabled", there is no problem. If >I compile with optimzations set to anything else (Maximize Speed, Minimize Size, >Full Optimizations), the program crashes due to a loop never terminating. The >source code is at the end of this message. The line where the problem occurs is: > >for (row = 11; row < 12; row--) > >The problem is the comparison: row < 12 > >When optimizations are turned off, this is the assembly output for that >comparison: > >cmp DWORD PTR _row$[ebp], 12 > >If optimizations are turned on, this is the assembly output: > >cmp ebx, OFFSET FLAT:_a+576 > >I'm no assembly expert, but that looks like it is comparing the address of two >pointers to me, and has nothing to do with comparing two values. > >Here is the example C source code. I compiled it under GCC with and without >optimizations and it ran fine. Another person with MSVC .NET 2003 ran this code >and he reported the same problem of crashing with optimizations turned on. > >Is this really an optimization bug, or is it possible that I am doing something >wrong with the compiler settings? If this is indeed an optimization bug, how can >I find out if Microsoft is already aware of it? If they are not aware of it, how >can I report it to them? I posted a message here: http://communities2.microsoft.com/communities/newsgroups/en-us/default.aspx?dg=microsoft.public.dotnet.languages.vc&cat=en-us-visualtoolsandlanguages-visualcplusplus&lang=en&cr=US I think probably someone will find it and act on it.
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