Bug#54667: Unnecessary signal handler redefinition

POSIX requires that a signal handler defined with sigaction()
is not reset on delivering a signal unless SA_NODEFER or
SA_RESETHAND is set. It is therefore unnecessary to redefine
the handler on signal delivery on platforms where sigaction()
is used without those flags.

include/my_alarm.h

@@ -36,14 +36,14 @@ extern ulong my_time_to_wait_for_lock;
 #define ALARM_END	VOID(signal(SIGALRM,alarm_signal)); \
 			VOID(alarm(alarm_old));
 #define ALARM_TEST	my_have_got_alarm
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
 #define ALARM_REINIT	VOID(alarm(MY_HOW_OFTEN_TO_ALARM)); \
 			VOID(signal(SIGALRM,my_set_alarm_variable));\
 			my_have_got_alarm=0;
 #else
 #define ALARM_REINIT	VOID(alarm((uint) MY_HOW_OFTEN_TO_ALARM)); \
 			my_have_got_alarm=0;
-#endif /* DONT_REMEMBER_SIGNAL */
+#endif /* SIGNAL_HANDLER_RESET_ON_DELIVERY */
 #else
 #define ALARM_VARIABLES long alarm_pos=0,alarm_end_pos=MY_HOW_OFTEN_TO_WRITE-1
 #define ALARM_INIT

include/my_global.h

@@ -541,8 +541,8 @@ extern "C" int madvise(void *addr, size_t len, int behav);
 #endif
 
 /* Does the system remember a signal handler after a signal ? */
-#ifndef HAVE_BSD_SIGNALS
-#define DONT_REMEMBER_SIGNAL
+#if !defined(HAVE_BSD_SIGNALS) && !defined(HAVE_SIGACTION)
+#define SIGNAL_HANDLER_RESET_ON_DELIVERY
 #endif
 
 /* Define void to stop lint from generating "null effekt" comments */

libmysql/libmysql.c

@@ -328,7 +328,7 @@ sig_handler
 my_pipe_sig_handler(int sig __attribute__((unused)))
 {
   DBUG_PRINT("info",("Hit by signal %d",sig));
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
   (void) signal(SIGPIPE, my_pipe_sig_handler);
 #endif
 }

mysys/thr_alarm.c

@@ -306,7 +306,7 @@ sig_handler process_alarm(int sig __attribute__((unused)))
 #if defined(MAIN) && !defined(__bsdi__)
     printf("thread_alarm in process_alarm\n"); fflush(stdout);
 #endif
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
     my_sigset(thr_client_alarm, process_alarm);	/* int. thread system calls */
 #endif
     return;
@@ -325,7 +325,7 @@ sig_handler process_alarm(int sig __attribute__((unused)))
 #endif
   process_alarm_part2(sig);
 #ifndef USE_ALARM_THREAD
-#if defined(DONT_REMEMBER_SIGNAL) && !defined(USE_ONE_SIGNAL_HAND)
+#if defined(SIGNAL_HANDLER_RESET_ON_DELIVERY) && !defined(USE_ONE_SIGNAL_HAND)
   my_sigset(THR_SERVER_ALARM,process_alarm);
 #endif
   pthread_mutex_unlock(&LOCK_alarm);
@@ -523,12 +523,12 @@ void thr_alarm_info(ALARM_INFO *info)
 */
 
 
-static sig_handler thread_alarm(int sig)
+static sig_handler thread_alarm(int sig __attribute__((unused)))
 {
 #ifdef MAIN
   printf("thread_alarm\n"); fflush(stdout);
 #endif
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
   my_sigset(sig,thread_alarm);		/* int. thread system calls */
 #endif
 }
@@ -797,7 +797,7 @@ static sig_handler print_signal_warning(int sig)
 {
   printf("Warning: Got signal %d from thread %s\n",sig,my_thread_name());
   fflush(stdout);
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
   my_sigset(sig,print_signal_warning);		/* int. thread system calls */
 #endif
   if (sig == SIGALRM)

sql/mysqld.cc

@@ -1232,7 +1232,7 @@ extern "C" sig_handler print_signal_warning(int sig)
 {
   if (global_system_variables.log_warnings)
     sql_print_warning("Got signal %d from thread %ld", sig,my_thread_id());
-#ifdef DONT_REMEMBER_SIGNAL
+#ifdef SIGNAL_HANDLER_RESET_ON_DELIVERY
   my_sigset(sig,print_signal_warning);		/* int. thread system calls */
 #endif
 #if !defined(__WIN__) && !defined(__NETWARE__)