Fix some warnings on Windows

Author: chfast

libff/algebra/curves/curve_utils.tcc

@@ -16,7 +16,7 @@ GroupT scalar_mul(const GroupT &base, const bigint<m> &scalar)
     GroupT result = GroupT::zero();
 
     bool found_one = false;
-    for (long i = scalar.max_bits() - 1; i >= 0; --i)
+    for (long i = static_cast<long>(scalar.max_bits() - 1); i >= 0; --i)
     {
         if (found_one)
         {

libff/algebra/fields/bigint.tcc

@@ -158,7 +158,7 @@ bool bigint<n>::test_bit(const std::size_t bitno) const
         const std::size_t part = bitno/GMP_NUMB_BITS;
         const std::size_t bit = bitno - (GMP_NUMB_BITS*part);
         const mp_limb_t one = 1;
-        return (this->data[part] & (one<<bit));
+        return (this->data[part] & (one<<bit)) != 0;
     }
 }
 

libff/algebra/fields/field_utils.tcc

@@ -189,7 +189,7 @@ void batch_invert(std::vector<FieldT> &vec)
 
     FieldT acc_inverse = acc.inverse();
 
-    for (long i = vec.size()-1; i >= 0; --i)
+    for (long i = static_cast<long>(vec.size()-1); i >= 0; --i)
     {
         const FieldT old_el = vec[i];
         vec[i] = acc_inverse * prod[i];

libff/algebra/fields/fp.tcc

@@ -196,7 +196,7 @@ Fp_model<n,modulus>::Fp_model(const bigint<n> &b)
 template<mp_size_t n, const bigint<n>& modulus>
 Fp_model<n,modulus>::Fp_model(const long x, const bool is_unsigned)
 {
-    static_assert(std::numeric_limits<mp_limb_t>::max() >= std::numeric_limits<long>::max(), "long won't fit in mp_limb_t");
+    static_assert(std::numeric_limits<mp_limb_t>::max() >= static_cast<unsigned long>(std::numeric_limits<long>::max()), "long won't fit in mp_limb_t");
     if (is_unsigned || x >= 0)
     {
         this->mont_repr.data[0] = (mp_limb_t)x;

libff/algebra/fields/fp4.tcc

@@ -189,7 +189,7 @@ Fp4_model<n, modulus> Fp4_model<n,modulus>::cyclotomic_exp(const bigint<m> &expo
     bool found_nonzero = false;
     std::vector<long> NAF = find_wnaf(1, exponent);
 
-    for (long i = NAF.size() - 1; i >= 0; --i)
+    for (long i = static_cast<long>(NAF.size() - 1); i >= 0; --i)
     {
         if (found_nonzero)
         {

libff/algebra/fields/fp6_2over3.tcc

@@ -219,7 +219,7 @@ Fp6_2over3_model<n, modulus> Fp6_2over3_model<n,modulus>::cyclotomic_exp(const b
     bool found_nonzero = false;
     std::vector<long> NAF = find_wnaf(1, exponent);
 
-    for (long i = NAF.size() - 1; i >= 0; --i)
+    for (long i = static_cast<long>(NAF.size() - 1); i >= 0; --i)
     {
         if (found_nonzero)
         {

libff/common/utils.hpp

@@ -25,7 +25,7 @@ size_t get_power_of_two(size_t n);
 /// returns ceil(log2(n)), so 1ul<<log2(n) is the smallest power of 2, that is not less than n
 size_t log2(size_t n);
 
-inline size_t exp2(size_t k) { return 1ul << k; }
+inline size_t exp2(size_t k) { return size_t(1) << k; }
 
 size_t to_twos_complement(int i, size_t w);
 int from_twos_complement(size_t i, size_t w);