fix: prevent widening of stored tag type in value assignment; update test output handling

Signed-off-by: YongDo-Hyun <froster12@naver.com>

3 files changed, 8 insertions, 10 deletions

diff --git a/src/value.cpp b/src/value.cpp
index 273049baf9..f07e28d82c 100644
--- a/src/value.cpp
+++ b/src/value.cpp
@@ -98,17 +98,12 @@ namespace // helper functions local to this translation unit
         auto incoming_type = detail::get_primitive_type<T>::value;
 
         // If the existing tag is of a narrower type than the incoming type,
-        // replace it with a new tag of the incoming type so the value is not
-        // truncated. Otherwise set the existing tag (possibly narrowing).
+        // reject the assignment to avoid widening the stored tag type.
         auto existing_type = tag_ptr->get_type();
 
         if(static_cast<int>(existing_type) < static_cast<int>(incoming_type))
         {
-            // replace with a new, wider tag that preserves the value
-            tag_ptr = make_numeric_tag(incoming_type, val);
-            if(!tag_ptr)
-                throw std::bad_cast();
-            return;
+            throw std::bad_cast();
         }
 
         // Existing type is same or wider: write into the existing tag (may narrow)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 41549842cb..500b939d51 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -62,6 +62,7 @@ build_data(DATA_OBJECTS
     trailing_data.zlib
 )
 add_library(NbtTestData STATIC ${DATA_OBJECTS})
+set_property(TARGET NbtTestData PROPERTY LINKER_LANGUAGE CXX)
 
 #Specifies that the directory containing the testfiles get copied when the target is built
 function(use_testfiles target)
diff --git a/test/format_test.cpp b/test/format_test.cpp
index 1a689ed3f2..ed8d2d1bfc 100644
--- a/test/format_test.cpp
+++ b/test/format_test.cpp
@@ -87,15 +87,17 @@ int main()
 
     // Write to file and read back
     {
+        tag_compound file_comp = comp;
+        file_comp.erase("null");
         std::ofstream out("test_output.nbt", std::ios::binary);
-        nbt::io::write_compound(out, comp);
+        nbt::io::write_tag("root", file_comp, out);
     }
 
     {
         std::ifstream in("test_output.nbt", std::ios::binary);
-        auto [read_comp, name] = nbt::io::read_compound(in);
+        auto read_pair = nbt::io::read_compound(in);
         std::cout << "----- read back from file:\n";
-        std::cout << read_comp;
+        std::cout << *read_pair.second;
         std::cout << "\n-----" << std::endl;
     }