Fix -Wsign-compare issues

src/pngchunk_int.cpp

@@ -190,7 +190,8 @@ namespace Exiv2 {
                 string_from_unterminated((const char*)(data.pData_ + Safe::add(keysize, 3)), languageTextMaxSize);
             const size_t languageTextSize = languageText.size();
 
-            enforce(data.size_ >= Safe::add(static_cast<size_t>(Safe::add(keysize, 4)), languageTextSize),
+            enforce(static_cast<unsigned long>(data.size_) >=
+                    Safe::add(static_cast<size_t>(Safe::add(keysize, 4)), languageTextSize),
                     Exiv2::kerCorruptedMetadata);
             // translated keyword string after the language description
             std::string translatedKeyText =

unitTests/test_futils.cpp

@@ -132,7 +132,8 @@ TEST(base64decode, decodesValidString)
     const std::string original ("VGhpcyBpcyBhIHVuaXQgdGVzdA==");
     const std::string expected ("This is a unit test");
     char * result = new char [original.size()];
-    ASSERT_EQ(expected.size()+1, base64decode(original.c_str(), result, original.size()));
+    ASSERT_EQ(static_cast<long>(expected.size()+1),
+              base64decode(original.c_str(), result, original.size()));
     ASSERT_STREQ(expected.c_str(), result);
     delete [] result;
 }