Fix 'typeset -p' output of compound array types (#453)

This bugfix was backported from ksh93v- 2012-10-04. The bug fixed
by this change is one that causes 'typeset -p' to omit the -C flag
when listing compound arrays belonging to a type:

   $ typeset -T Foo_t=(compound -a bar)
   $ Foo_t baz
   $ typeset -p baz.bar
   typeset -a baz.bar=''  # This should be 'typeset -C -a'

src/cmd/ksh93/sh/nvtype.c:
- Backport change from 93v- 2012-10-04 that sets the array nvalue to
  a pointer named Null (which is "") in nv_mktype(), then to Empty
  in fixnode().
- Change the Null name from the 93v- code to AltEmpty to avoid
  misleading code readers into thinking that it's a null pointer.

src/cmd/ksh93/tests/types.sh:
- Backport the relevant 93v- changes to the types regression tests.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

NEWS

@@ -14,10 +14,13 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   an incompletely defined 'foo_t' built-in comamnd that will crash the shell
   when used. Instead, it is now silently ignored for backwards compatibility.
 
-- A bug in which the output of a two dimensional sparse indexed array would
+- Compound arrays belonging to a type created with 'typeset -T' now have
-  cause the second subscript to be treated as an associative array when read
+  their -C attribute preserved in the output of 'typeset -p'.
-  back in has been fixed. Elements that are sparse indexed arrays are now
+
-  prefixed with "typeset -a".
+- A bug has been fixed in which the 'typeset -p' output of a two-dimensional
+  sparse indexed array would cause the second subscript to be treated as an
+  associative array when read back in by the shell. Elements that are sparse
+  indexed arrays are now prefixed with "typeset -a".
 
 2022-02-05:
 

src/cmd/ksh93/sh/nvtype.c

@@ -139,6 +139,8 @@ static const Namdisc_t type_disc =
 	0,
 };
 
+static char *AltEmpty = "";
+
 size_t nv_datasize(Namval_t *np, size_t *offset)
 {
 	size_t s=0, a=0;
@@ -333,6 +335,8 @@ static int fixnode(Namtype_t *dp, Namtype_t *pp, int i, struct Namref *nrp,int f
 				nv_offattr(nq,NV_NOFREE);
 			}
 		}
+		else if(nq->nvalue.cp==AltEmpty)
+			nq->nvalue.cp = Empty;
 		else if(nq->nvalue.cp==Empty)
 			nv_offattr(nq,NV_NOFREE);
 	
@@ -1159,7 +1163,12 @@ Namval_t *nv_mktype(Namval_t **nodes, int numnodes)
 					free((void*)np->nvalue.cp);
 			}
 			if(!nq->nvalue.cp && nq->nvfun== &pp->childfun.fun)
-				nq->nvalue.cp = Empty;
+			{
+				if(nv_isattr(np,NV_ARRAY|NV_NOFREE)==(NV_ARRAY|NV_NOFREE))
+					nq->nvalue.cp = AltEmpty;
+				else
+					nq->nvalue.cp = Empty;
+			}
 			np->nvalue.cp = 0;
 			offset += (dsize?dsize:4);
 		}

src/cmd/ksh93/tests/types.sh

@@ -592,7 +592,7 @@ $SHELL << \EOF
 			 compound p=( hello=world )
 			 c.b.binsert p 1 $i
 		done
-		exp='typeset -C c=(board_t b=(typeset -a board_y=( [1]=(typeset -a board_x=( [0]=(field=(hello=world;))[1]=(field=(hello=world)));));))'
+		exp='typeset -C c=(board_t b=(typeset -C -a board_y=( [1]=(typeset -a board_x=( [0]=(field=(hello=world;))[1]=(field=(hello=world)));));))'
 		[[ $(typeset -p c) == "$exp" ]] || exit 1
 	}
 	main
@@ -634,6 +634,13 @@ Bar_t bar
 bar.foo+=(bam)
 [[ ${bar.foo[0]} == bam ]] || err_exit 'appending to empty array variable in type does not create element 0'
 
+# ======
+# Compound arrays listed with 'typeset -p' should have their -C attribute
+# preserved in the output.
+typeset -T Z_t=(compound -a x)
+Z_t z
+[[ $(typeset -p z.x) ==  *'-C -a'* ]] || err_exit 'typeset -p for compound array element does not display all attributes'
+
 # ======
 # Type names that have 'a' as the first letter should be functional
 "$SHELL" -c 'typeset -T al=(typeset bar); al foo=(bar=testset)' || err_exit "type names that start with 'a' don't work"