GNU bug report logs - #33564
Incorrect path canonicalisation

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Mattias Andrée <maandree <at> kth.se>
To: bug-gnu-emacs <at> gnu.org
Subject: Incorrect path canonicalisation
Date: Sat, 1 Dec 2018 21:04:50 +0100

Emacs 26.1 removes ..'s incorrectly from file names.
Emacs removes the directory in front the .. rather than
getting its parent directory.

Example:

	cd
	mkdir -p 1/2
	cd 1/2
	echo 3 > ../../3
	ln -s ~ 4
	echo 5 > 5
	emacs 4/../5 # works, but shouldn't
	emacs 4/../$USER/3 # does not works, should

On Linux, the proper way to get the canonical path
for a file with the file descriptor $fd:

	stat(3) /dev/fd/$fd
	p := readlink(3) /dev/fd/$fd
	if (st_nlinks != 0) {
		stat(3) /dev/fd/$fd
		if (st_nlinks == 0) {
			p := readlink(3) /dev/fd/$fd
			remove " (deleted)" from the end of p
		}
	} else {
		remove " (deleted)" from the end of p
	}
	canonical path is p

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