Should I set errno?

Question

I\'m writing a module which exports an interface similar to send and recv.

Since those functions are supposed to return respectively the nu

Answer 1

Actually, you probably can do "proper" (as you put it) error management since you return an int.

Just use non-negative values for the number of bytes read or written and negative values for error codes. You don't have to limit yourself to -1:

enum myerrors {
    ERR_NO_MEMORY    = -1,
    ERR_BAD_ARGS     = -2,
    ERR_CPU_EXPLODED = -3,
    // and so on
};

However, setting errno in the fashion you want is valid. The standard states that errno expands to a modifiable lvalue, meaning you can set it. From C1x/n1425, 7.5 Errors :

... and errno which expands to a modifiable lvalue that has type int, the value of which is set to a positive error number by several library functions.