[ruby-dev:45780] Re: [ruby-changes:24083] nobu:r36134 (trunk): process.c: no method calls in async-signal-safe

2012/6/19 nobu <[e-mail]>:
> nobu    2012-06-19 17:51:57 +0900 (Tue, 19 Jun 2012)
>
>  New Revision: 36134
>
>  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=rev&revision=36134
>
>  Log:
>    process.c: no method calls in async-signal-safe
>
>    * process.c (rb_execarg_run_options): do not call any methods in the
>      async-signal-safe function.  mask has been checked with NUM2MODET()
>      already and converted with LONG2NUM().

> Index: process.c
> ===================================================================
> --- process.c   (revision 36133)
> +++ process.c   (revision 36134)
> @@ -17,6 +17,8 @@
>  #include "internal.h"
>  #include "vm_core.h"
>
> +#define STATIC_ASSERT(name, expr) typedef int static_assert_##name##_check[1 - 2*!(expr)]
> +
>  #include <stdio.h>
>  #include <errno.h>
>  #include <signal.h>
> @@ -1595,6 +1597,7 @@
>                                   hide_obj(rb_str_dup(val)));
>         }
>         else if (id == rb_intern("umask")) {
> +           STATIC_ASSERT(sizeof_mode_t, sizeof(long) >= sizeof(mode_t)); /* for LONG2NUM */
>            mode_t cmask = NUM2MODET(val);
>             if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_UMASK))) {
>                 rb_raise(rb_eArgError, "umask option specified twice");
> @@ -2707,7 +2710,7 @@
>
>     obj = rb_ary_entry(options, EXEC_OPTION_UMASK);
>     if (!NIL_P(obj)) {
> -        mode_t mask = NUM2MODET(obj);
> +        mode_t mask = (mode_t)FIX2LONG(obj); /* no method calls */
>         mode_t oldmask = umask(mask); /* never fail */ /* async-signal-safe */
>         if (!NIL_P(soptions))
>             rb_ary_store(soptions, EXEC_OPTION_UMASK, MODET2NUM(oldmask));

どういう状況でこの NUM2MODET からメソッド呼び出しが起こるのか
理解できなかったんですが、どういう話なんでしょう?
-- 
[田中 哲][たなか あきら][Tanaka Akira]