mksh R50c: parser fixes break common “set -u” workaround

[Thorsten Glaser]

tglase@tglase:~ $ MODULESDIR=/lib/modules/3.16-2-amd64
tglase@tglase:~ $ dir=kernel/drivers/scsi
tglase@tglase:~ $ exclude=
tglase@tglase:~ $ kmods=$(find "${MODULESDIR}/${dir}" ${exclude} -name '*.ko' -printf '%f\n')
tglase@tglase:~ $ kmods=$(find "${MODULESDIR}/${dir}" ${exclude:-} -name '*.ko' -printf '%f\n')
find: cannot search `': No such file or directory

${exclude:-} now generates a field where it previously didn’t.

[Thorsten Glaser (mirabilos)]

Cause: https://github.com/MirBSD/mksh/commit/968dc7a764b1bd6a39411caaab54036513c264f0 eval.c changes (1.151 → 1.152)

Possibly this:

tglase@tglase:~ $ showargs() { for i; do echo -n " <$i>"; done; echo; }
tglase@tglase:~ $ IFS=:; showargs 1 ${-+:foo:bar}
 <1> <> <foo> <bar>
tglase@tglase:~ $ IFS=' '; showargs 1 ${-+ foo bar}
 <1> <> <foo> <bar>
tglase@tglase:~ $ ksh93
ksh93$ showargs() { for i; do echo -n " <$i>"; done; echo; }
ksh93$ IFS=:; showargs 1 ${-+:foo:bar}
 <1> <> <foo> <bar>
ksh93$ IFS=' '; showargs 1 ${-+ foo bar}
 <1> <foo> <bar>
ksh93$
tglase@tglase:~ $ bash
bash$ showargs() { for i; do echo -n " <$i>"; done; echo; }
bash$ IFS=:; showargs 1 ${-+:foo:bar}
 <1> <> <foo> <bar>
bash$ IFS=' '; showargs 1 ${-+ foo bar}
 <1> <foo> <bar>

Only IFS_NWS should generate a field.

[Thorsten Glaser (mirabilos)]

fixed in R50d