bignum.c (rb_int_powm): Integer#pow(0, 1) should return 0

... instead of 1 because it requires "modulo 1".  [Bug #17257]

1 files changed, 2 insertions, 0 deletions

diff --git a/bignum.c b/bignum.c
index 65a50ea9ba..cd969ac360 100644
--- a/bignum.c
+++ b/bignum.c
@@ -7136,6 +7136,7 @@ rb_int_powm(int const argc, VALUE * const argv, VALUE const num)
             long const half_val = (long)HALF_LONG_MSB;
             long const mm = FIX2LONG(m);
             if (!mm) rb_num_zerodiv();
+            if (mm == 1) return INT2FIX(0);
             if (mm <= half_val) {
                 return int_pow_tmp1(rb_int_modulo(a, m), b, mm, nega_flg);
             }
@@ -7145,6 +7146,7 @@ rb_int_powm(int const argc, VALUE * const argv, VALUE const num)
         }
         else {
             if (rb_bigzero_p(m)) rb_num_zerodiv();
+	    if (bignorm(m) == INT2FIX(1)) return INT2FIX(0);
             return int_pow_tmp3(rb_int_modulo(a, m), b, m, nega_flg);
         }
     }