fix(VarHolder): MSVC warning #4886 (#4903)

* fix(VarHolder): MSVC warning #4886

* fix(VarHolder): do not convert unsigned #4886

* chore(SocketImpl): eliminate MSVC warning

* fix(VarHolder): do not convert unsigned (extract unpreserveSign()) #4886

* chore(testsuite): eliminate MSVC warnings

* chore(VarHolder): simplify unpreserveSign using constexpr.

---------

Co-authored-by: Matej Kenda <matejken@gmail.com>

Foundation/include/Poco/Dynamic/VarHolder.h

@@ -469,13 +469,32 @@ protected:
 
 private:
 
-	template <typename T, std::enable_if_t<std::is_integral_v<T>, bool> = true>
+	template <typename T>
+	static constexpr T unpreserveSign(const T& value)
+	{
+		if constexpr (std::is_signed_v<T>)
+		{
+			return (value < 0) ? -value : value;
+		}
+		else
+		{
+			return value;
+		}
+	}
+
+	template <typename T, std::enable_if_t<std::is_same_v<T, bool>, bool> = true>
+	static constexpr int numValDigits(const T& value)
+	{
+		return 1;
+	}
+
+	template <typename T, std::enable_if_t<std::is_integral_v<T> && !std::is_same_v<T, bool>, bool> = true>
 	static constexpr int numValDigits(const T& value)
 	{
 		using U = std::make_unsigned_t<T>;
 		if (value == 0) return 0;
 		int digitCount = 0;
-		U locVal = (std::is_signed_v<T> && value < 0) ? -value : value; // to prevent sign preservation
+		U locVal = static_cast<U>(unpreserveSign(value)); // to prevent sign preservation
 		while (locVal >>= 1) ++digitCount;
 		return digitCount;
 	}

Foundation/include/Poco/String.h

@@ -400,7 +400,7 @@ int icompare(
 	typename S::size_type pos,
 	const typename S::value_type* ptr)
 {
-	int n = pos < str.size() ? str.size() - pos : 0;
+	int n = static_cast<int>(pos < str.size() ? str.size() - pos : 0);
 	return icompare(str, pos, n, ptr);
 }
 

Foundation/testsuite/src/ArrayTest.cpp

@@ -60,7 +60,7 @@ void ArrayTest::testConstruction()
 
 	for (std::size_t i=0; i<g.size(); ++i)
 	{
-		g[i]._data = i;
+		g[i]._data = static_cast<int>(i);
 	}
 
 	for (std::size_t i=0; i<g.size(); ++i)

Foundation/testsuite/src/CoreTest.cpp

@@ -217,7 +217,7 @@ void CoreTest::testBuffer()
 	std::vector<int> v;
 	for (std::size_t i = 0; i < s; ++i)
 	{
-		v.push_back(i);
+		v.push_back(static_cast<int>(i));
 	}
 
 	std::memcpy(b.begin(), v.data(), sizeof(int) * v.size());
@@ -241,7 +241,7 @@ void CoreTest::testBuffer()
 	v.clear();
 	for (std::size_t i = 0; i < s*2; ++i)
 	{
-		v.push_back(i);
+		v.push_back(static_cast<int>(i));
 	}
 
 	std::memcpy(b.begin(), v.data(), sizeof(int) * v.size());

Foundation/testsuite/src/ProcessRunnerTest.cpp

@@ -277,7 +277,7 @@ void ProcessRunnerTest::testProcessRunner()
 			{
 				pr.reset(new ProcessRunner(cmd, args));
 				failmsg("ProcessRunner should throw an exception.");
-			} catch(const Poco::FileException& e) {}
+			} catch(const Poco::FileException&) {}
 		}
 		assertTrue (!File(pidFile).exists());
 	}
@@ -295,7 +295,7 @@ void ProcessRunnerTest::testProcessRunner()
 			{
 				pr.reset(new ProcessRunner(cmd, args));
 				failmsg("ProcessRunner should throw an exception.");
-			} catch(const Poco::FileException& e) {}
+			} catch(const Poco::FileException&) {}
 		}
 		assertTrue (!File(pidFile).exists());
 	}

Net/src/SocketImpl.cpp

@@ -1566,7 +1566,7 @@ std::streamsize SocketImpl::sendFileBlockwise(FileInputStream& fileInputStream,
 	while (n > 0 && (count == 0 || len < count))
 	{
 		len += n;
-		sendBytes(buffer.begin(), n);
+		sendBytes(buffer.begin(), static_cast<int>(n));
 		if (count > 0 && len < count)
 		{
 			const std::size_t remaining = count - len;