To solve the incompatibility issues between mksh-current, old mksh versions

and vendor pdksh versions, re-introduce FPOSIX alongside FSH. The semantics
are now:
‣ set -o posix ⇒
  • disable brace expansion and FSH when triggered
  • use Debian Policy 10.4 compliant non-XSI “echo” builtin
  • do not keep file descriptors > 2 to ksh
‣ set -o sh ⇒
  • set automatically #ifdef MKSH_BINSHREDUCED
  • disable brace expansion and FPOSIX when triggered
  • use Debian Policy 10.4 compliant non-XSI “echo” builtin
  • do not keep file descriptors > 2 to ksh
  • trigger MKSH_MIDNIGHTBSD01ASH_COMPAT mode if compiled in
  • make “set -- $(getopt ab:c "$@")” construct work

Note that the set/getopt one used to behave POSIXly only with FSH or
FPOSIX (depending on the mksh version) set and Bourne-ish with it not
set, so this changes default mksh behaviour to POSIX!

check.t

@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.356 2010/01/25 14:25:13 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.357 2010/01/28 15:18:46 tg Exp $
 # $OpenBSD: bksl-nl.t,v 1.2 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: history.t,v 1.5 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: read.t,v 1.3 2003/03/10 03:48:16 david Exp $
@@ -3088,6 +3088,38 @@ stdin:
 expected-stdout:
 	bye
 ---
+name: regression-10
+description:
+	The following:
+		set -- `false`
+		echo $?
+	should print 0 according to POSIX (dash, bash, ksh93, posh)
+	but not 0 according to the getopt(1) manual page, ksh88, and
+	Bourne sh (such as /bin/sh on Solaris).
+	In mksh R39b, we honour POSIX except when -o sh is set.
+stdin:
+	showf() {
+		[[ -o posix ]]; FPOSIX=$((1-$?))
+		[[ -o sh ]]; FSH=$((1-$?))
+		echo -n "FPOSIX=$FPOSIX FSH=$FSH "
+	}
+	set +o posix +o sh
+	showf
+	set -- `false`
+	echo rv=$?
+	set -o sh
+	showf
+	set -- `false`
+	echo rv=$?
+	set -o posix
+	showf
+	set -- `false`
+	echo rv=$?
+expected-stdout:
+	FPOSIX=0 FSH=0 rv=0
+	FPOSIX=0 FSH=1 rv=1
+	FPOSIX=1 FSH=0 rv=0
+---
 name: regression-11
 description:
 	The following:
@@ -4377,35 +4409,6 @@ expected-stdout:
 	E 0
 	F 0
 ---
-name: exit-subst-1
-description:
-	Used to be regression-10 but was split into two tests.
-	The following:
-		set -- `false`
-		echo $?
-	should print 0 according to POSIX, but not 0 according to /bin/sh
-	(XXX on which system?), AT&T ksh88, and the getopt(1) manual page
-stdin:
-	set -- `false`
-	echo $?
-expected-stdout:
-	1
----
-name: exit-subst-2
-description:
-	Used to be regression-10 but was split into two tests.
-	The following:
-		set -- `false`
-		echo $?
-	should print 0 according to POSIX, but not 0 according to /bin/sh
-	(XXX on which system?), AT&T ksh88, and the getopt(1) manual page
-stdin:
-	test -n "$POSH_VERSION" || set -o sh
-	set -- `false`
-	echo $?
-expected-stdout:
-	0
----
 name: test-stlt-1
 description:
 	Check that test also can handle string1 < string2 etc.

funcs.c

@@ -25,7 +25,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.149 2010/01/25 14:38:01 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.150 2010/01/28 15:18:48 tg Exp $");
 
 #if HAVE_KILLPG
 /*
@@ -539,7 +539,7 @@ c_print(const char **wp)
 	if (wp[0][0] == 'e') {
 		/* echo builtin */
 		wp++;
-		if (Flag(FSH)) {
+		if (Flag(FPOSIX) || Flag(FSH)) {
 			/* Debian Policy 10.4 compliant "echo" builtin */
 			if (*wp && !strcmp(*wp, "-n")) {
 				/* we recognise "-n" only as the first arg */
@@ -2372,8 +2372,9 @@ c_set(const char **wp)
 	 * which assumes the exit value set will be that of the $()
 	 * (subst_exstat is cleared in execute() so that it will be 0
 	 * if there are no command substitutions).
+	 * Switched ksh (!posix !sh) to POSIX in mksh R39b.
 	 */
-	return (Flag(FSH) ? 0 : subst_exstat);
+	return (Flag(FSH) ? subst_exstat : 0);
 }
 
 int
@@ -2572,8 +2573,12 @@ c_exec(const char **wp MKSH_A_UNUSED)
 		for (i = 0; i < NUFILE; i++) {
 			if (e->savefd[i] > 0)
 				close(e->savefd[i]);
-			/* For ksh (but not sh), keep anything > 2 private */
-			if (!Flag(FSH) && i > 2 && e->savefd[i])
+			/*
+			 * keep all file descriptors > 2 private for ksh,
+			 * but not for POSIX or legacy/kludge sh
+			 */
+			if (!Flag(FPOSIX) && !Flag(FSH) && i > 2 &&
+			    e->savefd[i])
 				fcntl(i, F_SETFD, FD_CLOEXEC);
 		}
 		e->savefd = NULL;

main.c

@@ -33,7 +33,7 @@
 #include <locale.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/main.c,v 1.160 2010/01/25 14:38:02 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/main.c,v 1.161 2010/01/28 15:18:48 tg Exp $");
 
 extern char **environ;
 
@@ -322,7 +322,7 @@ mksh_init(int argc, const char *argv[])
 		if (!(s->start = s->str = argv[argi++]))
 			errorf("-c requires an argument");
 #ifdef MKSH_MIDNIGHTBSD01ASH_COMPAT
-		/* compatibility to MidnightBSD 0.1 /bin/sh (not desired) */
+		/* compatibility to MidnightBSD 0.1 /bin/sh (kludge) */
 		if (Flag(FSH) && argv[argi] && !strcmp(argv[argi], "--"))
 			++argi;
 #endif

misc.c

@@ -29,7 +29,7 @@
 #include <grp.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/misc.c,v 1.136 2010/01/25 14:07:39 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/misc.c,v 1.137 2010/01/28 15:18:49 tg Exp $");
 
 unsigned char chtypes[UCHAR_MAX + 1];	/* type bits for unsigned char */
 
@@ -232,8 +232,9 @@ change_flag(enum sh_flag f, int what, unsigned int newval)
 		setegid(kshegid = kshgid = getgid());
 		setgid(kshegid);
 #endif
-	} else if (f == FSH && newval) {
-		Flag(FBRACEEXPAND) = 0;
+	} else if ((f == FPOSIX || f == FSH) && newval) {
+		Flag(FPOSIX) = Flag(FSH) = Flag(FBRACEEXPAND) = 0;
+		Flag(f) = (unsigned char)newval;
 	}
 	/* Changing interactive flag? */
 	if (f == FTALKING) {

mksh.1

@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.211 2010/01/27 18:36:19 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.212 2010/01/28 15:18:50 tg Exp $
 .\" $OpenBSD: ksh.1,v 1.129 2009/05/28 06:09:06 jmc Exp $
 .\"-
 .\" Copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
@@ -71,7 +71,7 @@
 .\" with -mandoc, it might implement .Mx itself, but we want to
 .\" use our own definition. And .Dd must come *first*, always.
 .\"
-.Dd $Mdocdate: January 27 2010 $
+.Dd $Mdocdate: January 28 2010 $
 .\"
 .\" Check which macro package we use
 .\"
@@ -2333,6 +2333,8 @@ will print an error with a line number prepended to it:
 .Pp
 File descriptors created by input/output redirections are private to the
 Korn shell, but passed to sub-processes if
+.Fl o Ic posix
+or
 .Fl o Ic sh
 is set.
 .Ss Arithmetic expressions
@@ -3129,6 +3131,8 @@ enables backslash interpretation (a no-op, since this is normally done), and
 suppresses backslash interpretation.
 .Pp
 If the
+.Ic posix
+or
 .Ic sh
 option is set, only the first argument is treated as an option, and only
 if it is exactly
@@ -3903,10 +3907,17 @@ See the
 and
 .Ic pwd
 commands above for more details.
+.It Ic posix
+Enable a somewhat more
+.Px
+like mode.
+As a side effect, setting this flag turns off
+.Ic braceexpand
+mode, which can be turned back on manually.
 .It Ic sh
 Enable
 .Pa /bin/sh
-.Pq POSIX/kludge
+.Pq kludge
 mode.
 Automatically enabled if the basename of the shell invocation begins with
 .Dq sh

sh_flags.h

@@ -1,5 +1,5 @@
 #if defined(SHFLAGS_DEFNS)
-__RCSID("$MirOS: src/bin/mksh/sh_flags.h,v 1.4 2009/10/02 18:08:37 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh_flags.h,v 1.5 2010/01/28 15:18:51 tg Exp $");
 #define FN(sname,cname,ochar,flags)	/* nothing */
 #elif defined(SHFLAGS_ENUMS)
 #define FN(sname,cname,ochar,flags)	cname,
@@ -89,13 +89,16 @@ FN("nounset", FNOUNSET, 'u', OF_ANY)
 /* ./.	don't do logical cds/pwds (non-standard) */
 FN("physical", FPHYSICAL, 0, OF_ANY)
 
+/* ./.	pdksh compat: somewhat more POSIXish mode (non-standard) */
+FN("posix", FPOSIX, 0, OF_ANY)
+
 /* -p	use suid_profile; privileged shell */
 FN("privileged", FPRIVILEGED, 'p', OF_ANY)
 
 /* -r	restricted shell */
 FN("restricted", FRESTRICTED, 'r', OF_CMDLINE)
 
-/* ./.	called as sh (some POSIX, some kludgy) not mksh (non-standard) */
+/* ./.	pdksh compat: called as sh not mksh; kludge mode (non-standard) */
 FN("sh", FSH, 0, OF_ANY)
 
 /* -s	(invocation) parse stdin (pseudo non-standard) */