将std :: error_code与整数进行比较

Question

My setup: macOS with Xcode/clang

From examples of std::error_code , it seems that it's compatible with enum, eg, you can assign an enum to it, but when comparing it with an integer like this:

if (my_error_code == 0)

I got

Invalid operands to binary expression ('const std::error_code' and 'int')

How should I test an error_code against a known integer such as errno s?

Answer 1

How should I test an error_code against a known integer such as errnos?

You should compare against the std::errc enum members that correspond to errno integers.

If for whatever reason you can't / don't want to do that, then compare against a new error_code constructed from the appropriate category and value .

Answer 2

std::error_code can't be compared with an int directly; you might want std::error_code::value to get the value of the error_code. (And you might also need the help of category .)

Returns the platform dependent error value.