As the Autoconf documentation says, "These days portable programs
[...] should not rely on `HAVE_RESTARTABLE_SYSCALLS', since nowadays
whether a system call is restartable is a dynamic issue, not a
configuration-time issue."
In other words, if we ever rely on HAVE_RESTARTABLE_SYSCALLS, we are
at the mercy of any code that Guile happens to be linked with, because
that code could install a signal handler without the SA_RESTART flag,
and then a Guile system call could unexpectedly return EINTR.
The readline part of this goes back to this problem report:
excellent example of the above paragraph. It was noted during the
discussion that undefining HAVE_RESTARTABLE_SYSCALLS would fix the
problem, but that solution wasn't adopted - I guess because Guile was
still using cooperative threads then (not pthreads) and so there was a
significant concern (whether founded or not) that not using
restartable syscalls (where available) could lead to a loss of
performance.
Now Guile's default mode of operation is with pthreads, where we
already don't assume that HAVE_RESTARTABLE_SYSCALLS is reliable, so
there is no possible further performance loss. And in any case we
really have no choice, if we want correct operation.
* configure.in (AC_SYS_RESTARTABLE_SYSCALLS): Removed.
* doc/ref/posix.texi (Signals): Remove statement that Guile always
sets SA_RESTART flag.
* guile-readline/configure.in (GUILE_SIGWINCH_SA_RESTART_CLEARED):
Remove this setting, together with its test code.
(HAVE_RL_PRE_INPUT_HOOK): Remove this setting and its code, as no
longer needed.
* guile-readline/readline.c (sigwinch_enable_restart): Removed.
(scm_init_readline): Remove setting of rl_pre_input_hook.
* libguile/_scm.h (SCM_SYSCALL): Remove the definition that relies on
HAVE_RESTARTABLE_SYSCALLS.
* libguile/scmsigs.c (scm_sigaction_for_thread): Don't always set the
SA_RESTART flag if available. Update docstring accordingly.
(scm_init_scmsigs): Remove code that sets SA_RESTART flag for all
signals.
actually microsecond accurate, remove warning usleep not always
available (guile has own code for it now, it's not the system call).
Cross reference scm_std_sleep / scm_std_usleep.
(Signals): Merge getitimer and setitimer, describe what
each timer does, use @defvar to get them indexed, caution may not
actually be microsecond accurate.
(Network Socket Address): New section, move sockaddr bits to here, add
new make-socket-address.
(Network Sockets and Communication): In connect, bind, and sendto, now
take socket address object. In bind, leave INADDR constants for
"Network Address Conversion" node. In those plus accept, getsockname,
getpeername, reword a bit for clarity.
(File System): In access?, reword a bit, clarify real
versus effective ID handling, cross reference glibc on that, and
recommend against access tests in library functions.
clarify the return is a pair with ports in car and cdr, note
connection is full duplex, refer to socket for parameters, refer to
PF_UNIX rather than AF_UNIX.
