Next round of minor tweaks and cleanups

Notable changes:
- Tie up some loose ends re: 3de4da5a and 7ba2c685.
- comp/omitted.c: Header include fix for Cygwin.
- misc/optget.c:
  - args(): When printing options for the uage line, use a local
    pointer for the 'if' block instead of reusing the 'b' pointer.
    That variable is used to output blanks later.
  - The above fix allows re-enabling the AST translation-aware
    macros and deleting the astsa fallback without causing usage
    message corruption in multibyte locales. Maybe someday we'll
    make ksh actually translatable.
  - Remove code to reinitialise _error_infop_ and _opt_info_
    'because these are not initialised by all DLLs'. In 2022,
    hopefully the buggy dynamic linkers are fixed. If not, we're
    not going to find out by keeping the workaround. I suspect that
    those bugs may have been triggered by the Microsoft/Cygwin
    import/export obfuscation removed in 3de4da5a.
- ksh93:
  - Remove unused sh.st.var_local variable. This was a leftover of
    a 93v- attempt to implement the bash 'local' command. It used
    static scoping, so it's not actually compatible.
  - Add a few regression tests for miscellaneous breakage that I
    caused in experiments (the breakage never made it to git; the
    tests are just to keep it that way).

src/cmd/ksh93/bltins/misc.c

@@ -287,7 +287,7 @@ int    b_dot_cmd(register int n,char *argv[],Shbltin_t *context)
 	}
 	*prevscope = sh.st;
 	sh.st.lineno = np?((struct functnod*)nv_funtree(np))->functline:1;
-	sh.st.var_local = sh.st.save_tree = sh.var_tree;
+	sh.st.save_tree = sh.var_tree;
 	if(filename)
 	{
 		sh.st.filename = filename;

src/cmd/ksh93/include/argnod.h

@@ -113,7 +113,6 @@ struct argnod
 /* legal argument flags */
 #define ARG_RAW		0x1	/* string needs no processing */
 #define ARG_MAKE	0x2	/* bit set during argument expansion */
-#define ARG_COMSUB	0x2	/* command sub */
 #define ARG_MAC		0x4	/* string needs macro expansion */
 #define	ARG_EXP		0x8	/* string needs file expansion */
 #define ARG_ASSIGN	0x10	/* argument is an assignment */

src/cmd/ksh93/include/shell.h

@@ -195,7 +195,6 @@ struct sh_scoped
 	int		lineno;
 	Dt_t		*save_tree;	/* var_tree for calling function */
 	struct sh_scoped *self;		/* pointer to copy of this scope */
-	Dt_t		*var_local;	/* local level variables for name() */
 	struct slnod	*staklist;	/* link list of function stacks */
 	int		states;		/* shell state bits used by sh_isstate(), etc. */
 	int		breakcnt;	/* number of levels to 'break'/'continue' (negative if 'continue') */

src/cmd/ksh93/sh/xec.c

@@ -2804,18 +2804,6 @@ int sh_trace(register char *argv[], register int nl)
 	return(0);
 }
 
-/*
- * This routine creates a subshell by calling fork() or vfork()
- * If ((flags&COMMSK)==TCOM), then vfork() is permitted
- * If fork fails, the shell sleeps for exponentially longer periods
- *   and tries again until a limit is reached.
- * SH_FORKLIM is the max period between forks - power of 2 usually.
- * Currently shell tries after 2,4,8,16, and 32 seconds and then quits
- * Failures cause the routine to error exit.
- * Parent links to here-documents are removed by the child
- * Traps are reset by the child
- * The process-id of the child is returned to the parent, 0 to the child.
- */
 static void timed_out(void *handle)
 {
 	NOT_USED(handle);
@@ -2954,6 +2942,17 @@ pid_t _sh_fork(register pid_t parent,int flags,int *jobid)
 	return(0);
 }
 
+/*
+ * This routine creates a subshell by calling fork(2).
+ * If fork fails, the shell sleeps for exponentially longer periods
+ *   and tries again until a limit is reached.
+ * SH_FORKLIM is the max period between forks - power of 2 usually.
+ * Currently, the shell tries after 2, 4, 8, 16 and 32 seconds, and then quits.
+ * Failures cause the routine to error exit.
+ * Parent links to here-documents are removed by the child.
+ * Traps are reset by the child.
+ * The process-id of the child is returned to the parent, 0 to the child.
+ */
 pid_t sh_fork(int flags, int *jobid)
 {
 	register pid_t parent;
@@ -3109,7 +3108,6 @@ int sh_funscope(int argn, char *argv[],int(*fun)(void*),void *arg,int execflg)
 	sh_pushcontext(buffp,SH_JMPFUN);
 	errorpush(&buffp->err,0);
 	error_info.id = argv[0];
-	sh.st.var_local = sh.var_tree;
 	if(!fun)
 	{
 		if(fp->node->nvalue.rp)

src/cmd/ksh93/tests/arith.sh

@@ -983,5 +983,11 @@ float x
        exit 0
 EOF
 
+# ======
+got=$(set +x; eval ': $((1 << 2))' 2>&1) \
+|| err_exit "bitwise left shift operator fails to parse (got $(printf %q "$got"))"
+got=$(set +x; eval 'got=$( ((y=1<<4)); echo $y )' 2>&1; echo $got) \
+|| err_exit "bitwise left shift operator fails to parse in comsub (got $(printf %q "$got"))"
+
 # ======
 exit $((Errors<125?Errors:125))

src/cmd/ksh93/tests/attributes.sh

@@ -385,7 +385,8 @@ done
 
 unset v
 typeset -H v=/dev/null
-[[ $v == *nul* ]] || err_exit 'typeset -H for /dev/null not working'
+# on cygwin, this is \\.\GLOBALROOT\Device\Null
+[[ $v == *[Nn]ul* ]] || err_exit "typeset -H for /dev/null not working (got $(printf %q "$v"))"
 
 unset x
 (typeset +C x) 2> /dev/null && err_exit 'typeset +C should be an error' 

src/cmd/ksh93/tests/subshell.sh

@@ -790,16 +790,17 @@ hash -r
 
 # ======
 # Variables set in functions inside of a virtual subshell should not affect the
-# outside environment. This regression test must be run from the disk.
-testvars=$tmp/testvars.sh
-cat >| "$testvars" << 'EOF'
+# outside environment. This regression test must be run as a separate script.
+got=$("$SHELL" -c '
 c=0
 function set_ac { a=1; c=1; }
 function set_abc { ( set_ac ; b=1 ) }
 set_abc
 echo "a=$a b=$b c=$c"
-EOF
-v=$($SHELL $testvars) && [[ "$v" == "a= b= c=0" ]] || err_exit 'variables set in subshells are not confined to the subshell'
+')
+exp='a= b= c=0'
+[[ $got == "$exp" ]] || err_exit 'variables set in subshells are not confined to the subshell' \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
 
 # ======
 got=$("$SHELL" -c '

src/cmd/ksh93/tests/variables.sh

@@ -1424,5 +1424,12 @@ do
 	done
 done
 
+# ======
+var1.get() { .sh.value=one; : $var2; }
+var2.get() { .sh.value=two; }
+got=$var1
+unset var1 var2
+[[ $got == one ]] || err_exit ".sh.value not restored after second .get discipline call (got $(printf %q "$got"))"
+
 # ======
 exit $((Errors<125?Errors:125))