revert r31760 and r31761

seems that rb_bug_errno() is called in sigpipe() intentionally.
https://gist.github.com/sorah/831169

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51390 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

process.c

@@ -1136,30 +1136,10 @@ proc_detach(VALUE obj, VALUE pid)
     return rb_detach_process(NUM2PIDT(pid));
 }
 
-#ifdef SIGPIPE
-static RETSIGTYPE (*saved_sigpipe_handler)(int) = 0;
-#endif
-
-#ifdef SIGPIPE
-static RETSIGTYPE
-sig_do_nothing(int sig)
-{
-}
-#endif
-
 /* This function should be async-signal-safe.  Actually it is. */
 static void
 before_exec_async_signal_safe(void)
 {
-#ifdef SIGPIPE
-    /*
-     * Some OS commands don't initialize signal handler properly. Thus we have
-     * to reset signal handler before exec(). Otherwise, system() and similar
-     * child process interaction might fail. (e.g. ruby -e "system 'yes | ls'")
-     * [ruby-dev:12261]
-     */
-    saved_sigpipe_handler = signal(SIGPIPE, sig_do_nothing); /* async-signal-safe */
-#endif
 }
 
 static void
@@ -1186,9 +1166,6 @@ before_exec(void)
 static void
 after_exec_async_signal_safe(void)
 {
-#ifdef SIGPIPE
-    signal(SIGPIPE, saved_sigpipe_handler); /* async-signal-safe */
-#endif
 }
 
 static void

signal.c

@@ -935,7 +935,7 @@ check_reserved_signal_(const char *name, size_t name_len)
 }
 #endif
 
-#ifdef SIGSYS
+#if defined SIGPIPE || defined SIGSYS
 static RETSIGTYPE
 sig_do_nothing(int sig)
 {
@@ -1066,7 +1066,7 @@ default_handler(int sig)
 #endif
 #ifdef SIGPIPE
       case SIGPIPE:
-        func = SIG_IGN;
+        func = sig_do_nothing;
         break;
 #endif
 #ifdef SIGSYS
@@ -1487,7 +1487,7 @@ Init_signal(void)
 #endif
     }
 #ifdef SIGPIPE
-    install_sighandler(SIGPIPE, SIG_IGN);
+    install_sighandler(SIGPIPE, sig_do_nothing);
 #endif
 #ifdef SIGSYS
     install_sighandler(SIGSYS, sig_do_nothing);