sh: Recognize "--" in . and exec.

Although "--" historically has not been required to be recognized for
certain special builtins that do not take options in POSIX, some other
implementations recognize options for them, requiring scripts to use "--" or
avoid operands starting with "-".

Operands starting with "-" can be avoided with eval by prepending a space,
and cannot occur with break, continue, exit, return and shift as they only
take numbers, nor with times as it does not take operands. With . and exec,
avoiding "-" is not so easy as it may require reimplementing the PATH
search; therefore the current proposal for POSIX is to require recognition
of "--" for them.

We continue to accept other strings starting with "-" as operands to . and
exec, and also "--" if it is alone to . (which would otherwise be invalid
anyway).

1 files changed, 6 insertions, 0 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index a47d045..e2f66ed 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -1170,6 +1170,12 @@ truecmd(int argc __unused, char **argv __unused)
 int
 execcmd(int argc, char **argv)
 {
+	/*
+	 * Because we have historically not supported any options,
+	 * only treat "--" specially.
+	 */
+	if (argc > 1 && strcmp(argv[1], "--") == 0)
+		argc--, argv++;
 	if (argc > 1) {
 		struct strlist *sp;