Fix arithmetic assignment operations for multidimensional indexed arrays (#296)

This PR corrects #168 for indexed arrays having more than one
level. Turns out ksh was only keeping track of the subscript number
for assignment in lvalue's nosub variable. By saving the actual
subscript reference, the result can be assigned to its proper
destination instead of putting the result into the last looked
value or subscript location.

src/cmd/ksh93/include/streval.h: struct lval:
- Create a new pointer named sub to hold the reference that nosub
  describes.

src/cmd/ksh93/sh/arith.c: arith():
- Adjust LOOKUP: for lvalue ARITH_ASSIGNOP operations on indexed
  arrays to save the np of the destination subscript for later use.
- Adjust ASSIGN: to act when lvalue's nosub > 0 which happens as
  the last step in the arithmetic parsing loop for assignment
  operations. Only indexed arrays will have a nosub value > 0. All
  others have a nosub of 0 unless they are involved in a unary
  operation (++, --) which sets nosub to -1. All said in the
  context of assignment operations like (( arr[0][1] += 1 )).

src/cmd/ksh93/sh/streval.c:
- Initialize the new sub pointer to 0.

src/cmd/ksh93/tests/arrays2.sh:
- Created a few multidimensional indexed array tests for assignment
  operations like += as an example.

Resolves: https://github.com/ksh93/ksh/issues/168

NEWS

@@ -23,6 +23,8 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   of declaration built-ins. This reverts a change introduced on 2020-09-11.
   [*] https://austingroupbugs.net/view.php?id=1393
 
+- Fixed arithmetic assignment operations for multidimensional indexed arrays
+
 2021-04-30:
 
 - The emacs 'ESC .' (M-.) and vi '_' commands now take shell quoting into

src/cmd/ksh93/include/streval.h

@@ -76,6 +76,7 @@ struct lval
 	const char	*expr;
 	const  void	*ptr;
 	int		nosub;
+	char		*sub;
 	short		flag;
 	short		nargs;
 	short		emode;

src/cmd/ksh93/sh/arith.c

@@ -233,8 +233,17 @@ static Sfdouble_t arith(const char **ptr, struct lval *lvalue, int type, Sfdoubl
 	{
 	    case ASSIGN:
 	    {
-		register Namval_t *np = (Namval_t*)(lvalue->value);
+		register Namval_t *np;
+		if (lvalue->nosub > 0 && lvalue->sub) /* indexed array ARITH_ASSIGNOP */
+		{
+			np = (Namval_t*)lvalue->sub; /* use saved subscript reference instead of last worked value */
+			nv_putsub(np, NIL(char*), lvalue->nosub-1);
+		}
+		else
+		{
+			np = (Namval_t*)lvalue->value;
 			np = scope(np, lvalue, 1);
+		}
 		nv_putval(np, (char*)&n, NV_LDOUBLE);
 		if(lvalue->eflag)
 			lvalue->ptr = (void*)nv_hasdisc(np,&ENUM_disc);
@@ -494,7 +503,10 @@ static Sfdouble_t arith(const char **ptr, struct lval *lvalue, int type, Sfdoubl
 		else if(nv_isattr(np,NV_DOUBLE)==NV_DOUBLE)
 			lvalue->isfloat=1;
 		if((lvalue->emode&ARITH_ASSIGNOP) && nv_isarray(np))
-			lvalue->nosub = nv_aindex(np)+1;
+		{
+			lvalue->nosub = nv_aindex(np)+1; /* subscript number of array */
+			lvalue->sub = (char*)np; /* store subscript reference for upcoming iteration of ASSIGN */
+		}
 		return(r);
 	    }
 

src/cmd/ksh93/sh/streval.c

@@ -172,6 +172,7 @@ Sfdouble_t	arith_exec(Arith_t *ep)
 	node.elen = ep->elen;
 	node.value = 0;
 	node.nosub = 0;
+	node.sub = 0;
 	node.ptr = 0;
 	node.eflag = 0;
 	if(shp->arithrecursion++ >= MAXLEVEL)

src/cmd/ksh93/tests/arrays2.sh

@@ -240,5 +240,24 @@ foo
 EOF
 $SHELL "$multiarray_unset" > /dev/null || err_exit 'Multidimensional arrays with an unset method crash ksh'
 
+# ======
+# Multidimensional indexed array arithmetic assignment operation tests
+ini() { unset arr; typeset -a arr=((10 20) 6 8); }
+[[ $( ini; ((arr[0][0]+=1)); typeset -p arr) == 'typeset -a arr=((11 20) 6 8)' ]] || err_exit 'ASSIGNOP: arr[0][0]+=1 failed.'
+[[ $( ini; ((arr[0][1]+=1)); typeset -p arr) == 'typeset -a arr=((10 21) 6 8)' ]] || err_exit 'ASSIGNOP: arr[0][1]+=1 failed.'
+[[ $( ini; ((arr[0][2]+=1)); typeset -p arr) == 'typeset -a arr=((10 20 1) 6 8)' ]] || err_exit 'ASSIGNOP: arr[0][2]+=1 failed.'
+[[ $( ini; ((arr[0][1]+=arr[1])); typeset -p arr) == 'typeset -a arr=((10 26) 6 8)' ]] || err_exit 'ASSIGNOP: arr[0][1]+=arr[1] failed.'
+[[ $( ini; ((arr[0][2]+=arr[1])); typeset -p arr) == 'typeset -a arr=((10 20 6) 6 8)' ]] || err_exit 'ASSIGNOP: arr[0][2]+=arr[1] failed.'
+[[ $( ini; ((arr[1]+=1)); typeset -p arr) == 'typeset -a arr=((10 20) 7 8)' ]] || err_exit 'ASSIGNOP: arr[1]+=1 failed.'
+[[ $( ini; ((arr[2]+=1)); typeset -p arr) == 'typeset -a arr=((10 20) 6 9)' ]] || err_exit 'ASSIGNOP: arr[2]+=1 failed.'
+[[ $( ini; ((arr[3]+=1)); typeset -p arr) == 'typeset -a arr=((10 20) 6 8 1)' ]] || err_exit 'ASSIGNOP: arr[3]+=1 failed.'
+[[ $( ini; ((arr[1]+=arr[0][0])); typeset -p arr) == 'typeset -a arr=((10 20) 16 8)' ]] || err_exit 'ASSIGNOP: arr[1]+=arr[0][0] failed.'
+[[ $( ini; ((arr[1]+=arr[0][1])); typeset -p arr) == 'typeset -a arr=((10 20) 26 8)' ]] || err_exit 'ASSIGNOP: arr[1]+=arr[0][1] failed.'
+[[ $( ini; ((arr[2]+=arr[0][0])); typeset -p arr) == 'typeset -a arr=((10 20) 6 18)' ]] || err_exit 'ASSIGNOP: arr[2]+=arr[0][0] failed.'
+[[ $( ini; ((arr[2]+=arr[0][1])); typeset -p arr) == 'typeset -a arr=((10 20) 6 28)' ]] || err_exit 'ASSIGNOP: arr[2]+=arr[0][1] failed.'
+[[ $( ini; ((arr[3]+=arr[0][1])); typeset -p arr) == 'typeset -a arr=((10 20) 6 8 20)' ]] || err_exit 'ASSIGNOP: arr[2]+=arr[0][1] failed.'
+unset arr
+unset -f ini
+
 # ======
 exit $((Errors<125?Errors:125))