Fix crash when listing indexed arrays with 'typeset -a'

There is a bug in print_scan() function that may cause ksh to crash
while listing indexed arrays. The crash happens in nv_search() when
called from print_scan().

This applies a fix from Siteshwar Vashist:
https://www.mail-archive.com/ast-developers@lists.research.att.com/msg01944.html

src/cmd/ksh93/bltins/typeset.c:
- Call nv_scan() without the NV_IARRAY flag, even for a null scan.

src/cmd/ksh93/tests/arrays.sh:
- Add regression test for 'typeset -a' crash and check output.

NEWS

@@ -7,6 +7,8 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 - Fixed a crash on syntax error when sourcing/dotting multiple files.
 
+- Fixed a crash when listing indexed arrays.
+
 2020-07-07:
 
 - Four of the date formats accepted by 'printf %()T' have had their

src/cmd/ksh93/bltins/typeset.c

@@ -1497,7 +1497,7 @@ static void print_scan(Sfio_t *file, int flag, Dt_t *root, int option,struct tda
 		tp->scanmask |= (NV_DOUBLE|NV_EXPNOTE);
 	if(flag==NV_LTOU || flag==NV_UTOL)
 		tp->scanmask |= NV_UTOL|NV_LTOU;
-	namec = nv_scan(root,nullscan,(void*)tp,tp->scanmask,flag);
+	namec = nv_scan(root, nullscan, (void*)tp, tp->scanmask, flag&~NV_IARRAY);
 	argv = tp->argnam  = (char**)stkalloc(tp->sh->stk,(namec+1)*sizeof(char*));
 	namec = nv_scan(root, pushname, (void*)tp, tp->scanmask, flag&~NV_IARRAY);
 	if(mbcoll())

src/cmd/ksh93/tests/arrays.sh

@@ -666,4 +666,13 @@ typeset -A Foo
 Foo=( [a]=AA;[b]=BB)
 [[ ${Foo[a]} == AA ]] || err_exit 'Fooa[a] is {Foo[a]} not AA' 
 
+# ======
+# Crash when listing an indexed array
+expect=$'A=($\'\\\'\')\nB=(aa)\nC=(aa)'
+actual=$("$SHELL" -c 'A[0]="'\''" B[0]=aa C[0]=aa; typeset -a') \
+	|| err_exit "Crash when listing indexed array (exit status $?)"
+[[ $actual == "$expect" ]] || err_exit 'Incorrect output when listing indexed array' \
+	"(expected $(printf %q "$expect"), got $(printf %q "$actual"))"
+
+# ======
 exit $((Errors<125?Errors:125))