Re: [bug-ncurses] Return value of write() is not properly evaluated

[Dr. Werner Fink]

On Wed, Dec 31, 2014 at 01:27:32PM +0100, Egmont Koblinger wrote:
> Off:
> 
> I find it bizarre that pretty much every piece of software has to
> reimplement this "restart on short read/write or interrupt" pattern,
> yet there's no convenience wrapper for this in any library I'm aware
> of.

There is, from info pages of libc:

 -- Macro: TEMP_FAILURE_RETRY (EXPRESSION)
     This macro evaluates EXPRESSION once, and examines its value as
     type `long int'.  If the value equals `-1', that indicates a
     failure and `errno' should be set to show what kind of failure.
     If it fails and reports error code `EINTR', `TEMP_FAILURE_RETRY'
     evaluates it again, and over and over until the result is not a
     temporary failure.

     The value returned by `TEMP_FAILURE_RETRY' is whatever value
     EXPRESSION produced.


Sidemark[1]: repeating without a usleep() on EAGAIN can cause a high load.
Sidemark[2]: using `_BSD_SOURCE' or `_GNU_SOURCE' or with latest glibc
             simply using SA_RESTART the problem should not occur

> 
> On Wed, Dec 31, 2014 at 11:37 AM, Stian Skjelstad
> <address@hidden> wrote:
> > Rebuilding the debian package without optimization made debug easier :-)
> >
> > With the following patch applied, output is perfect, and no visual noise is
> > present (my software refreshes the screen at a typical rate of 20 fps,
> > typical with changes on every refresh). Checking with strace, it now pushes
> > out the write buffers completely, also when receiving signals like SIGALRM
> >
> >
> > --
> > Stian Skjelstad
> >
> > _______________________________________________
> > Bug-ncurses mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/bug-ncurses
> >
> 
> _______________________________________________
> Bug-ncurses mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/bug-ncurses

-- 
 Dr. Werner Fink -- Software Engineer Consultant
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