The below is a bug initially reported by Xuefer at
https://bugs.gentoo.org/646412.
Reproducer:
$ mv --version
mv (GNU coreutils) 8.31
Packaged by Gentoo (8.31 (p0))
$ touch a.aa
$ ln a.aa b.bb
$ mv a.aa b.bb
mv: 'a.aa' and 'b.bb' are the same file
For comparison if fines are unrelated 'mv' just works:
$ touch a.aa
$ touch b.bb
$ mv a.aa b.bb
$ echo $?
0
Fun fact: busybox does not complain about hardlinked files:
$ touch a.aa
$ ln a.aa b.bb
$ busybox mv a.aa b.bb
$ echo $?
$ echo $?
0
Some context on where these accidentally hardlinked files come from:
gdb build system simplistically does the following:
$ gcc a.c -o a.tmp.o && mv a.tmp.o a.o
ccache has a mode to create a resulting file by hardlinking
if possible instead of copying data round.
If the above command is ran without ccache wrapper 'a.tmp.o'
is always a new file. Otherwise if it's ran via ccache with
CCACHE_HARDLINK=1 then 'a.tmp.o' and 'a.o' and both
hardlinks of a file stored in cache originally.
Is it an 'mv's bug or a feature to prevent hardlinked file clobbering?
If feels like an unnecessary restriction.
Thank you!
--
Sergei
