cpp: Add is_zero() and explicit bool() for basic types

include/evmc/evmc.hpp

@@ -24,6 +24,9 @@ struct address : evmc_address
     ///
     /// Initializes bytes to zeros if not other @p init value provided.
     constexpr address(evmc_address init = {}) noexcept : evmc_address{init} {}
+
+    /// Explicit operator converting to bool.
+    constexpr inline explicit operator bool() const noexcept;
 };
 
 /// The fixed size array of 32 bytes for storing 256-bit EVM values.
@@ -35,6 +38,9 @@ struct bytes32 : evmc_bytes32
     ///
     /// Initializes bytes to zeros if not other @p init value provided.
     constexpr bytes32(evmc_bytes32 init = {}) noexcept : evmc_bytes32{init} {}
+
+    /// Explicit operator converting to bool.
+    constexpr inline explicit operator bool() const noexcept;
 };
 
 /// Loads 64 bits / 8 bytes of data from the given @p bytes array in big-endian order.
@@ -118,6 +124,28 @@ constexpr bool operator<(const bytes32& a, const bytes32& b) noexcept
             load64be(&a.bytes[24]) < load64be(&b.bytes[24]));
 }
 
+/// Checks if the given address is the zero address.
+constexpr inline bool is_zero(const address& a) noexcept
+{
+    return a == address{};
+}
+
+constexpr address::operator bool() const noexcept
+{
+    return !is_zero(*this);
+}
+
+/// Checks if the given bytes32 object has all zero bytes.
+constexpr inline bool is_zero(const bytes32& a) noexcept
+{
+    return a == bytes32{};
+}
+
+constexpr bytes32::operator bool() const noexcept
+{
+    return !is_zero(*this);
+}
+
 
 /// @copydoc evmc_result
 ///

test/unittests/test_cpp.cpp

@@ -21,6 +21,9 @@ TEST(cpp, address)
 {
     evmc::address a;
     EXPECT_EQ(std::count(std::begin(a.bytes), std::end(a.bytes), 0), sizeof(a));
+    EXPECT_TRUE(is_zero(a));
+    EXPECT_FALSE(a);
+    EXPECT_TRUE(!a);
 
     auto other = evmc_address{};
     other.bytes[19] = 0xfe;
@@ -30,12 +33,18 @@ TEST(cpp, address)
     a.bytes[0] = 1;
     other = a;
     EXPECT_TRUE(std::equal(std::begin(a.bytes), std::end(a.bytes), std::begin(other.bytes)));
+    EXPECT_FALSE(is_zero(a));
+    EXPECT_TRUE(a);
+    EXPECT_FALSE(!a);
 }
 
 TEST(cpp, bytes32)
 {
     evmc::bytes32 b;
     EXPECT_EQ(std::count(std::begin(b.bytes), std::end(b.bytes), 0), sizeof(b));
+    EXPECT_TRUE(is_zero(b));
+    EXPECT_FALSE(b);
+    EXPECT_TRUE(!b);
 
     auto other = evmc_bytes32{};
     other.bytes[31] = 0xfe;
@@ -45,6 +54,9 @@ TEST(cpp, bytes32)
     b.bytes[0] = 1;
     other = b;
     EXPECT_TRUE(std::equal(std::begin(b.bytes), std::end(b.bytes), std::begin(other.bytes)));
+    EXPECT_FALSE(is_zero(b));
+    EXPECT_TRUE(b);
+    EXPECT_FALSE(!b);
 }
 
 TEST(cpp, std_hash)