Clarification on the Use of JSON_NOEXCEPTION vs. -fno-exceptions

[The0Dev]

Hello,

I’m a bit curious about the rationale behind the JSON_NOEXCEPTION macro. My understanding is that it doesn’t eliminate exceptions thrown by the standard library, which this library relies on. Why not simply check for -fno-exceptions instead? Am I missing something?

Thank you!

[nlohmann]

Then you compile the library with -fno-exceptions, you would get a compiler error like

error: exception handling disabled, use '-fexceptions' to enable

for the first occurrence of keywords like try, throw, or catch. The macro JSON_NOEXCEPTION replaces these keywords as described in https://nlohmann.github.io/json/api/macros/json_noexception/.

[The0Dev]

Alright, thanks. I thought those keywords were already replaced in this library when exceptions are disabled with -fno-exceptions or a similar option. I guess that may not always be the case (?)

#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
    #define JSON_THROW(exception) throw exception
    #define JSON_TRY try
    #define JSON_CATCH(exception) catch(exception)
    #define JSON_INTERNAL_CATCH(exception) catch(exception)
#else
    #include <cstdlib>
    #define JSON_THROW(exception) std::abort()
    #define JSON_TRY if(true)
    #define JSON_CATCH(exception) if(false)
    #define JSON_INTERNAL_CATCH(exception) if(false)
#endif