CHECK failed, how to use it correctly

[Howe2015]

this is my code

  std::string name = "a";
  std::cout <<"the result of std::isalpha(name[0]):"<< std::isalpha(name[0])<<std::endl;
  CHECK(std::isalpha(name[0])) << "name[0]:"<<name[0];

and the code core dump at the log

the result of std::isalpha(name[0]):1024
2021/04/16 16:30:51 317872	CONTRACT [main.cpp->main:66]	
	*******	 EXIT trigger caused by broken Contract: CHECK(std::isalpha(name[0]))
	"name[0]:a
*******	STACKDUMP *******

But when i use this code

  std::string name = "a";
  std::cout <<"the result of std::isalpha(name[0]):"<< std::isalpha(name[0])<<std::endl;
  //CHECK(std::isalpha(name[0])) << "name[0]:"<<name[0];
  CHECK(static_cast<bool>(std::isalpha(name[0]))) << "name[0]:"<<name[0];

it work ok.
How to use "CHECK" correctly.

[KjellKod]

Not sure what's going on. Potentially it's some weirdness with your platform.
I've tested this myself and

   std::string name = "a";
  std::cout <<"the result of std::isalpha(name[0]):"<< std::isalpha(name[0])<<std::endl;
  CHECK(std::isalpha(name[0])) << "name[0]:"<<name[0];
  CHECK(static_cast<bool>(std::isalpha(name[0]))) << "name[0]:"<<name[0];
  std::cout << "end of testing: static_cast<bool>(std::isalpha(name[0]): " << static_cast<bool>(std::isalpha(name[0])) << std::endl;

generates, as expected

the result of std::isalpha(name[0]):1
end of testing: static_cast<bool>(std::isalpha(name[0]): 1

[KjellKod]

What's your platform, compiler etc?

[KjellKod]

Interesting, I see it failing on Windows and Linux but passing on OSX. I.e. the is platform dependent behavior.
For cross platform maybe you should use the tools mentioned https://en.cppreference.com/w/cpp/string/byte/isalpha
I.e. maybe something like std::boolalpha and convert the answer to (bool)std::isalpha(c)

That isalpha is also locale dependent puts also restrictions on how you use the locale so the std::boolalpha would make the code safer.

I consider this a C++ std::library issue and not a g3log issue. I will close this

[Howe2015]

thanks @KjellKod