Another ^A bug

[Martijn Dekker]

That ^A / $'\1' character just keeps causing trouble...

This is a bug with IFS. Including a $'\1' character anywhere in IFS 
causes expansions in shell assignments to discard that character.

$ bash -c "c=$'Y\1Y';
    for IFS in $'\1' $'\2' $'x\1' $'x\2' $'\1x' $'\2x'; do
        v=X\${c}X;
        printf %s \"\$v\" | od -a | awk 'NR==1 { \$1=\"\"; print }';
    done"

Output on bash 4.4 and current git:
 X Y Y X
 X Y soh Y X
 X Y Y X
 X Y soh Y X
 X Y Y X
 X Y soh Y X

Expected output, on bash 4.3 and earlier, and all other shells:
 X Y soh Y X
 X Y soh Y X
 X Y soh Y X
 X Y soh Y X
 X Y soh Y X
 X Y soh Y X

Note that quoting the assigned value is an effective workaround. But in 
shell grammar, IFS should never have any influence on true shell 
assignments (as opposed to assignment-arguments) and quoting expansions 
should not be necessary. (This paragraph is included to pre-empt readers 
who would reply "just quote everything". Yes, I know. It's still a bug.)

Thanks,

- Martijn