Re: errno (was Re: C23 thoughts and opinions - why so conservative?)

David Brown <david.brown@hesbynett.no> writes:
[...]

The normal way for multi-threaded systems is to implement it as a
macro.   It might be, for example :
>
#define errno __thread_data->_errno
>
or
>
#define errno *errno()

Both of those need more parentheses -- and I'm unconfortable using the
same identifier for the macro and the function.

That is precisely why it is specified in the C standards as a macro,
not an external linkage object with static or thread-local storage
duration.   (The use of errno in multi-threading C code long predates
C11 and _Thread_local.)

[...]

glibc and musl both have :

    # define errno (*__errno_location ())

newlib (used on Cygwin) has something similar :

    #define errno (*__errno())

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */