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Date: Wed, 11 Jun 2025 16:01:51 -0700 (PDT)
X-X-Sender: jeremyd AT resin DOT csoft DOT net
To: cygwin AT cygwin DOT com
Subject: Path prefix //./ in Cygwin
Message-ID: <93fd79f3-bb39-79c2-8e78-57c4af356e54@jdrake.com>
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From: Jeremy Drake via Cygwin <cygwin AT cygwin DOT com>
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Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

While making some tests for a path parser in rust
(https://github.com/rust-lang/rust/pull/141864), an interesting corner
case in Cygwin path handling came to light:

Works:
\\.\C:
//.\C:
//./C:\foo

Doesn't work:
//./C:
//./C:/foo

It appears to be able to use the \\.\ prefix, there must be at least 1
backslash in the path.  Otherwise, it seems that . and .. are being
normalized like a normal path and //./C:/foo is treated like
//C:/foo.  The delay attempting to access it makes me think it is looking
for a server/share style path.

My question is whether this behavior is intentional or a bug.  I don't
want to see rust codify this in their path parser and tests, only to have
it change later as a bugfix in a corner case of path handling.

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