std::string can't be returned as NULL

[brechtsanders]

In StringTokenizer::GetNextToken() in Utilities/StringTokenizer.cpp the line return(NULL); is not correct as the function returns a std::string which can't be set to NULL..

In fact, GCC 12 will give the following error:

Utilities/StringTokenizer.cpp:238:28: error: use of deleted function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::nullptr_t) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::nullptr_t = std::nullptr_t]'

Changing the line return(NULL); to return(""); fixes this.

P.S.: I know GCC 12 isn't released yet, but the current stage 3 prerelease already works quite well.

[marxin]

Thanks for the report. I can confirm that GCC 12 is going to contain the change (adding libstdc++ maintainer @jwakely).

[jwakely]

The report is correct, constructing a std::string from a null pointer is undefined behaviour, and would throw in older versions of GCC (was this function ever even called?)

return "" or return std::string() or (since C++11) return {} would work

[marxin]

Note this is going to be an error only if -std=c++23 is used.

[jwakely]

But it's still undefined in all earlier versions of C++ if that code ever executes!

[jwakely]

You should still fix it!