"Norman Diamond" <ndiamond@community.nospam> wrote in message
news:OVZZDtU5HHA.5980@TK2MSFTNGP04.phx.gbl...
> After a call to Graphics.DrawImage, an OutOfMemory error might occur. The
> probability of an error has some correlation with the size of the image
> but is not reliable. Even with an image of a few hundred megabytes,
> sometimes the error occurs and sometimes not. Some random postings on the
> web and newsgroups say the image file is broken, well, the image file
> doesn't alternate between being broken and not. The error is
> intermittent.
>
> When running under a debugger, sometimes Visual Studio asserts that the
> error occured in some other random place such as Application.Run. But not
> always. So I think sometimes the stack is getting smashed.
>
> Now get this. Inserting some calls to GC.Collect *increases* the
> probability of an OutOfMemory error. Deleting those calls *decreases* the
> probability. This seems backwards, right? Well, not if the errors are
> due to one particular kind of bug.
>
> I think Graphics.DrawImage is forgetting to pin a pointer before calling a
> Win32 API. I think the garbage collector is collecting stuff that the
> Win32 API thought it was going to use.

"Michael C" <mike@nospam.com> wrote in message
news:ucesTES6HHA.5160@TK2MSFTNGP05.phx.gbl...
> "Norman Diamond" <ndiamond@community.nospam> wrote in message
> news:OVZZDtU5HHA.5980@TK2MSFTNGP04.phx.gbl...
>> After a call to Graphics.DrawImage, an OutOfMemory error might occur.
>> The probability of an error has some correlation with the size of the
>> image but is not reliable. Even with an image of a few hundred
>> megabytes, sometimes the error occurs and sometimes not. Some random
>> postings on the web and newsgroups say the image file is broken, well,
>> the image file doesn't alternate between being broken and not. The error
>> is intermittent.
>>
>> When running under a debugger, sometimes Visual Studio asserts that the
>> error occured in some other random place such as Application.Run. But
>> not always. So I think sometimes the stack is getting smashed.
>>
>> Now get this. Inserting some calls to GC.Collect *increases* the
>> probability of an OutOfMemory error. Deleting those calls *decreases*
>> the probability. This seems backwards, right? Well, not if the errors
>> are due to one particular kind of bug.
>>
>> I think Graphics.DrawImage is forgetting to pin a pointer before calling
>> a Win32 API. I think the garbage collector is collecting stuff that the
>> Win32 API thought it was going to use.
>
> It's possible memory is getting fragmented and while there is a lot of
> free memory there isn't a free contiguous block of memory. I'm not sure
> how to solve it though, I would have thought the GC.Collect would fix it.
> Maybe GC.Collect doesn't wait for the complete collection to occur.