erts: Change default of erl_crash.dump

* Create an erl_crash.dump if no heart exists
  and no ERL_CRASH_DUMP_SECONDS is set (behaviour changed)
* Don't create an erl_crash.dump if heart do exists
  and no ERL_CRASH_DUMP_SECONDS is set (behaviour not changed)

This changes the behaviour back to the R15B02 default considering
if a beam was running with no heart.

The motivation is that we want a fast heart to fast restart erlang if
it crashes but to be able to get non-truncated erl_crash.dumps via
setting ERL_CRASH_DUMP_SECONDS if we so desire.

2 files changed, 17 insertions, 3 deletions

diff --git a/erts/emulator/beam/break.c b/erts/emulator/beam/break.c
index cf66f4e6b6..f7e9f15655 100644
--- a/erts/emulator/beam/break.c
+++ b/erts/emulator/beam/break.c
@@ -657,6 +657,7 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
     char dumpnamebuf[MAXPATHLEN];
     char* dumpname;
     int secs;
+    int env_erl_crash_dump_seconds_set = 1;
 
     if (ERTS_SOMEONE_IS_CRASH_DUMPING)
 	return;
@@ -681,6 +682,8 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
 
     envsz = sizeof(env);
     /* ERL_CRASH_DUMP_SECONDS not set
+     * if we have a heart port, break immediately
+     * otherwise dump crash indefinitely (until crash is complete)
      * same as ERL_CRASH_DUMP_SECONDS = 0
      * - do not write dump
      * - do not set an alarm
@@ -702,8 +705,10 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
      */
 	
     if (erts_sys_getenv__("ERL_CRASH_DUMP_SECONDS", env, &envsz) != 0) {
-	return; /* break immediately */
+	env_erl_crash_dump_seconds_set = 0;
+	secs = -1;
     } else {
+	env_erl_crash_dump_seconds_set = 1;
 	secs = atoi(env);
     }
 
@@ -711,7 +716,16 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
 	return;
     }
 
-    erts_sys_prepare_crash_dump(secs);
+    /* erts_sys_prepare_crash_dump returns 1 if heart port is found, otherwise 0
+     * If we don't find heart (0) and we don't have ERL_CRASH_DUMP_SECONDS set
+     * we should continue writing a dump
+     *
+     * beware: secs -1 means no alarm
+     */
+
+    if (erts_sys_prepare_crash_dump(secs) && !env_erl_crash_dump_seconds_set ) {
+	return;
+    }
 
     if (erts_sys_getenv__("ERL_CRASH_DUMP",&dumpnamebuf[0],&dumpnamebufsize) != 0)
 	dumpname = "erl_crash.dump";
diff --git a/erts/emulator/beam/sys.h b/erts/emulator/beam/sys.h
index 9dd8341520..41389c8734 100644
--- a/erts/emulator/beam/sys.h
+++ b/erts/emulator/beam/sys.h
@@ -652,7 +652,7 @@ void erts_sys_schedule_interrupt_timed(int set, erts_short_time_t msec);
 void erts_sys_main_thread(void);
 #endif
 
-extern void erts_sys_prepare_crash_dump(int secs);
+extern int erts_sys_prepare_crash_dump(int secs);
 extern void erts_sys_pre_init(void);
 extern void erl_sys_init(void);
 extern void erl_sys_args(int *argc, char **argv);