1 files changed, 13 insertions, 5 deletions

diff --git a/shell/math.c b/shell/math.c
index e90a38f05..536f22ff0 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -585,12 +585,21 @@ static arith_t parse_with_base(const char *nptr, char **endptr, unsigned base)
                 nptr++;
         }
         *endptr = (char*)nptr;
+
         /* "64#" and "64#+1" used to be valid expressions, but bash 5.2.15
-         * no longer allow such, detect this:
+         * no longer allows such, detect this:
          */
-// NB: bash allows $((0x)), this is probably a bug...
-        if (nptr == start)
-                *endptr = NULL; /* there weren't any digits, bad */
+        if (nptr == start) {
+                /* There weren't any digits */
+                /* Excluding the case of "0x"
+                 * (bash allows 0x: supports 0x$hexdigits when $hexdigits is empty)
+                 */
+                if (base != 16 /* why check 16? for base 10, start[-1] is undefined */
+                 || (start[-1] | 0x20) != 'x'
+                )
+                        *endptr = NULL; /* error indicator */
+        }
+
         return n;
 }
 
@@ -611,7 +620,6 @@ static arith_t strto_arith_t(const char *nptr, char **endptr)
                         base = 16;
                         nptr += 2;
                 }
-// NB: bash allows $((0x)), this is probably a bug...
                 return parse_with_base(nptr, endptr, base);
         }