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).

2 files changed, 14 insertions, 2 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;
 
diff --git a/bin/sh/main.c b/bin/sh/main.c
index ecbb12d..15ee9e7 100644
--- a/bin/sh/main.c
+++ b/bin/sh/main.c
@@ -314,14 +314,20 @@ find_dot_file(char *basename)
 int
 dotcmd(int argc, char **argv)
 {
-	char *fullname;
+	char *filename, *fullname;
 
 	if (argc < 2)
 		error("missing filename");
 
 	exitstatus = 0;
 
-	fullname = find_dot_file(argv[1]);
+	/*
+	 * Because we have historically not supported any options,
+	 * only treat "--" specially.
+	 */
+	filename = argc > 2 && strcmp(argv[1], "--") == 0 ? argv[2] : argv[1];
+
+	fullname = find_dot_file(filename);
 	setinputfile(fullname, 1);
 	commandname = fullname;
 	cmdloop(0);