Merge #14510: Avoid triggering undefined behaviour in base_uint<BITS>::bits()

96f6dc9 Avoid triggering undefined behaviour in base_uint<BITS>::bits() (practicalswift)

Pull request description:

  Avoid triggering undefined behaviour in `base_uint<BITS>::bits()`.

  `1 << 31` is undefined behaviour in C++11.

  Given the reasonable assumption of `sizeof(int) * CHAR_BIT == 32`.

Tree-SHA512: 995fa38e71c8921873139ecf1b7dd54178555219af3be60d07290f379439ddd8479e3963c6f3cae8178efb61063a0f9add6cba82a5578d13888597b5bcd54f22

Author: laanwj

src/arith_uint256.cpp

@@ -176,7 +176,7 @@ unsigned int base_uint<BITS>::bits() const
     for (int pos = WIDTH - 1; pos >= 0; pos--) {
         if (pn[pos]) {
             for (int nbits = 31; nbits > 0; nbits--) {
-                if (pn[pos] & 1 << nbits)
+                if (pn[pos] & 1U << nbits)
                     return 32 * pos + nbits + 1;
             }
             return 32 * pos + 1;