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From: Beman Dawes (bdawes_at_[hidden])
Date: 2004-11-23 13:49:34

At 02:39 AM 11/22/2004, Daniel Krügler wrote:

>its quite a long time ago since I could follow the threads here more
>thoroughly :-( , so the following information might not be new one.
>During tests of the current Win32 implementation of
>boost::filesystem::equivalent I observed that the function unexpectingly
>fails (my test environment was Win XP SP 1 with MSVC7.1) if it compares
>a "soft link" created via the DOS command "subst" (or its API analogon
>::DefineDosDeviceA/W) with the corresponding mapped path object (Lets
>say I map M: to the existing directory C:\temp).
>To get an understanding of the test failure I debugged the
>implementation and found that actually the first test part (getting the
>handles and comparing the VSN's + further data) gave the expected
>positive result, but that the very last step, i.e. the comparison of
>both st_dev values, gave a final unequality.

Ugh! That's ugly.

>Did others also observe this failure

AFAIK, it is a new test case.

> and don't you think that the
>expected result should show the identity of the underlying path objects?
>Of course there might be legitimate arguments for the decision for the
>current behaviour, but I would like to know about them. I am not an
>expert to argue about the comments in the source code which say that
>"In theory, volume serial numbers are sufficient to distinguish between
>devices, but in practice VSN's are sometimes duplicated, so device id
> is also checked.[..]"
>The question now is: Should different (MS DOS) device names pointing to
>the same underlying (Windows NT) device not be compared equivalent?
>I could think of the following test extension (at least under Windows,
>regrettably I am not a posix expert to provide a similar solution):
>If the VSN' and further data have returned a positive result, but the
>check of both st_dev values fails, one should try to check whether the
>underlying devices are actually the same, e.g. using the
>::QueryDosDeviceA/W API function.
>What do you think?

Worth experimenting with. I'll try to dust of the test program and give it
a try.



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