Compiler warns of implicit fallthrough when defining preprocessor macro NDEBUG

[vpollex]

What is the issue you have?

GCC produces a warning that statement json.hpp:8394 may fall through when preprocessor macro NDEBUG is defined.

Please describe the steps to reproduce the issue.

1. Compile code example below with warning for implicit fallthrough enabled and defined preprocessor macro NDEBUG such that it uses the single-header file, eg. g++ -Wextra -DNDEBUG <filename>

Can you provide a small but working code example?

#include <nlohmann/json.hpp>

int main() {
        nlohmann::json j1 = R"({"compact": true, "schema": 0})"_json;
        nlohmann::json j2 = nlohmann::json::from_msgpack(nlohmann::json::to_msgpack(j1));
        return 0;
}

What is the expected behavior?

Compiler does not produce a warning, because a statement may fall through

And what is the actual behavior instead?

Compiler produces a warning, because a statement may fall through

Which compiler and operating system are you using?

• Compiler: g++ 7.5.0 / g++ 8.3.0 / g++ 10.1.0
• Operating system: Linux

Which version of the library did you use?

• latest release version 3.9.1
• other release - please state the version: ___
• the develop branch

If you experience a compilation error: can you compile and run the unit tests?

• yes
• no - please copy/paste the error message below