I'm still kind of new here, so forgive me if this is a silly question, but
why do this with a define and not an template function?
On Fri, May 1, 2009 at 12:35 PM, Adam Langley <a...@chromium.org> wrote:
>
> On POSIX systems, system calls can be interrupted by signals. In this case,
> they'll return EINTR, indicating that the system call needs to be
> restarted.
>
> (The situation is a little more complicated than this with SA_RESTART, but
> you
> can read man 7 signal if you like.)
>
> The short of it is that you need to catch EINTR and restart the call for
> these
> system calls:
>
> * read, readv, write, writev, ioctl
> * open() when dealing with a fifo
> * wait*
> * Anything socket based (send*, recv*, connect, accept etc)
> * flock and lock control with fcntl
> * mq_ functions which can block
> * futex
> * sem_wait (and timed wait)
> * pause, sigsuspend, sigtimedwait, sigwaitinfo
> * poll, epoll_wait, select and 'p' versions of the same
> * msgrcv, msgsnd, semop, semtimedop
> * close (although, on Linux, EINTR won't happen here)
> * any sleep functions (careful, you need to handle this are restart with
> different arguments)
>
> We've been a little sloppy with this until now. Once the tree reopens,
> I'll be
> landing 100225 which adds a macro for dealing with this and corrects every
> case
> of these system calls (that I found).
>
> The macro is HANDLE_EINTR in base/eintr_wrapper.h. It's safe to include on
> Windows and is a no-op there.
>
> On POSIX, it uses GCC magic to return the correct type based on the
> expression
> and restarts the system call if it throws EINTR. Here it is:
>
> #define HANDLE_EINTR(x) ({ \
> typeof(x) ret; \
> do { \
> ret = x; \
> } while (ret == -1 && errno == EINTR); \
> ret;\
> })
>
> And you can use it like:
> HANDLE_EINTR(close(fd));
>
> Or:
> ssize_t bytes_read = HANDLE_EINTR(read(fd, buffer, len));
>
>
>
> AGL
>
> >
>
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