What is __thread tls?

Zera William Holladay zholla1 at uic.edu
Mon Mar 14 18:16:39 PST 2005

On Mon, 14 Mar 2005, Matthew Dillon wrote:
> :I was under the impression that each pthread has its own errno???  Perhaps
> :I am not understanding the context.  I'm writing my first threaded
> :application so I had best get this straight sooner rather than later.
> :
> :-Zera
>     yup, you are right... see if you can figure out how errno is defined
>     for a threaded program in the current environment.  Hint: it isn't a
>     simple global declaration.

#define errno           (* __error()) /* errno.h */

For threaded applications (per the comment):

The function __error() returns a pointer to a field "error" in the pthread
structure (on line 712 of pthread_private.h).

Otherwise and for the main thread:

__error() is a pointer to a global variable.

If I'm right, then that's pretty cool! :)


> 					-Matt
> 					Matthew Dillon
> 					<dillon at xxxxxxxxxxxxx>

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