--- a/libtommath/bn_mp_sub.c	Tue May 26 23:27:26 2020 +0800
+++ b/libtommath/bn_mp_sub.c	Tue May 26 17:36:47 2020 +0200
@@ -1,24 +1,13 @@
 #include "tommath_private.h"
 #ifdef BN_MP_SUB_C
-/* LibTomMath, multiple-precision integer library -- Tom St Denis
- *
- * LibTomMath is a library that provides multiple-precision
- * integer arithmetic as well as number theoretic functionality.
- *
- * The library was designed directly after the MPI library by
- * Michael Fromberger but has been written from scratch with
- * additional optimizations in place.
- *
- * SPDX-License-Identifier: Unlicense
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* high level subtraction (handles signs) */
-int mp_sub(const mp_int *a, const mp_int *b, mp_int *c)
+mp_err mp_sub(const mp_int *a, const mp_int *b, mp_int *c)
 {
-   int     sa, sb, res;
-
-   sa = a->sign;
-   sb = b->sign;
+   mp_sign sa = a->sign, sb = b->sign;
+   mp_err err;
 
    if (sa != sb) {
       /* subtract a negative from a positive, OR */
@@ -26,7 +15,7 @@
       /* In either case, ADD their magnitudes, */
       /* and use the sign of the first number. */
       c->sign = sa;
-      res = s_mp_add(a, b, c);
+      err = s_mp_add(a, b, c);
    } else {
       /* subtract a positive from a positive, OR */
       /* subtract a negative from a negative. */
@@ -36,20 +25,16 @@
          /* Copy the sign from the first */
          c->sign = sa;
          /* The first has a larger or equal magnitude */
-         res = s_mp_sub(a, b, c);
+         err = s_mp_sub(a, b, c);
       } else {
          /* The result has the *opposite* sign from */
          /* the first number. */
          c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS;
          /* The second has a larger magnitude */
-         res = s_mp_sub(b, a, c);
+         err = s_mp_sub(b, a, c);
       }
    }
-   return res;
+   return err;
 }
 
 #endif
-
-/* ref:         HEAD -> master, tag: v1.1.0 */
-/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
-/* commit time: 2019-01-28 20:32:32 +0100 */