CharacterFunctions: Avoid UB when parsing hex strings

modules/juce_core/network/juce_IPAddress.cpp

@@ -166,7 +166,7 @@ IPAddress::IPAddress (const String& adr)
             }
 
             IPAddressByteUnion temp;
-            temp.combined = (uint16) CharacterFunctions::HexParser<int>::parse (tokens[i].getCharPointer());
+            temp.combined = CharacterFunctions::HexParser<uint16>::parse (tokens[i].getCharPointer());
 
             address[i * 2]     = temp.split[0];
             address[i * 2 + 1] = temp.split[1];

modules/juce_core/text/juce_CharacterFunctions.h

@@ -490,6 +490,9 @@ public:
     template <typename ResultType>
     struct HexParser
     {
+        static_assert (std::is_unsigned<ResultType>::value, "ResultType must be unsigned because "
+                                                            "left-shifting a negative value is UB");
+
         template <typename CharPointerType>
         static ResultType parse (CharPointerType t) noexcept
         {
@@ -497,10 +500,10 @@ public:
 
             while (! t.isEmpty())
             {
-                auto hexValue = CharacterFunctions::getHexDigitValue (t.getAndAdvance());
+                auto hexValue = static_cast<ResultType> (CharacterFunctions::getHexDigitValue (t.getAndAdvance()));
 
                 if (hexValue >= 0)
-                    result = (result << 4) | hexValue;
+                    result = static_cast<ResultType> (result << 4) | hexValue;
             }
 
             return result;

modules/juce_core/text/juce_String.cpp

@@ -1957,8 +1957,8 @@ String String::toHexString (const void* const d, const int size, const int group
     return s;
 }
 
-int   String::getHexValue32() const noexcept    { return CharacterFunctions::HexParser<int>  ::parse (text); }
-int64 String::getHexValue64() const noexcept    { return CharacterFunctions::HexParser<int64>::parse (text); }
+int   String::getHexValue32() const noexcept    { return (int32) CharacterFunctions::HexParser<uint32>::parse (text); }
+int64 String::getHexValue64() const noexcept    { return (int64) CharacterFunctions::HexParser<uint64>::parse (text); }
 
 //==============================================================================
 static String getStringFromWindows1252Codepage (const char* data, size_t num)

modules/juce_graphics/colour/juce_Colour.cpp

@@ -542,7 +542,7 @@ String Colour::toString() const
 
 Colour Colour::fromString (StringRef encodedColourString)
 {
-    return Colour ((uint32) CharacterFunctions::HexParser<int>::parse (encodedColourString.text));
+    return Colour (CharacterFunctions::HexParser<uint32>::parse (encodedColourString.text));
 }
 
 String Colour::toDisplayString (const bool includeAlphaValue) const