Fix weak-vtables warning (#4500)

* 🔧 remove warning suppression

* 🚨 fix weak-vtables warning #4087

* 🚨 suppress -Wweak-vtables warning

* 🚨 suppress -Wweak-vtables warning

* ✅ fix test

* ✅ fix test

* ✅ fix test

include/nlohmann/detail/exceptions.hpp

@@ -25,6 +25,18 @@
 #include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 
+// With -Wweak-vtables, Clang will complain about the exception classes as they
+// have no out-of-line virtual method definitions and their vtable will be
+// emitted in every translation unit. This issue cannot be fixed with a
+// header-only library as there is no implementation file to move these
+// functions to. As a result, we suppress this warning here to avoid client
+// code to stumble over this. See https://github.com/nlohmann/json/issues/4087
+// for a discussion.
+#if defined(__clang__)
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wweak-vtables"
+#endif
+
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
@@ -255,3 +267,7 @@ class other_error : public exception
 
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
+
+#if defined(__clang__)
+    #pragma clang diagnostic pop
+#endif