Assignment of -0 in arithmetic expansion doesn't remove negative sign

[laurenthuberdeau]

Assignment of -0 in arithmetic expansion assigns -0 to variables on ARM. ksh on x86 and other shells remove the negative sign, which makes me think it may be due to some undefined behavior like in #770.

This short example shows the bug.

> ksh
$ : $(( a = 0 ))
$ : $(( b = -0 ))
$ : $(( c = +0 ))
$ echo $a # print 0
0
$ echo $b # print -0 instead of 0
-0
$ echo $c # print 0 as expected
0

[ko1nksm]

Here is another example on Linux on x86_64. I don't think this includes undefined behavior.

$ ksh -c 'v=0; (( v = -1 * v )); echo $v'
-0

This issue may have been introduced between ksh93-2007-06-28 and ksh93-2007-11-05.

root@6eb222d646da:/# ksh93-2007-06-28 -c 'v=0; (( v = -1 * v )); echo $v'
0

root@6eb222d646da:/# ksh93-2007-11-05 -c 'v=0; (( v = -1 * v )); echo $v'
-0