Cleanup, fix checkpoint output.

stepmania/src/archutils/Unix/CrashHandler.cpp

@@ -102,7 +102,7 @@ static void parent_process( int to_child, void **BacktracePointers, int SignalRe
 	}
 
     /* 6. Write CHECKPOINTs. */
-    p = GetCheckpointLogs("$$");
+    p = GetCheckpointLogs("\n");
     size = strlen(p)+1;
     parent_write(to_child, &size, sizeof(size));
     parent_write(to_child, p, size);
@@ -387,7 +387,8 @@ static void do_backtrace(void **buf, size_t size)
 #warning Undefined BACKTRACE_METHOD_*
 static void do_backtrace(void **buf, size_t size)
 {
-    buf[0] = NULL;
+    buf[0] = BACKTRACE_METHOD_NOT_AVAILABLE;
+    buf[1] = NULL;
 }
 #endif
 

stepmania/src/archutils/Unix/CrashHandlerChild.cpp

@@ -274,6 +274,18 @@ void BacktraceNames::FromAddr( void *p )
 
 static void output_stack_trace( FILE *out, void **BacktracePointers )
 {
+	if( BacktracePointers[0] == BACKTRACE_METHOD_NOT_AVAILABLE )
+	{
+		fprintf( out, "No backtrace method available.\n");
+		return;
+	}
+
+	if( !BacktracePointers[0] )
+	{
+		fprintf( out, "Backtrace was empty.\n");
+		return;
+	}
+
     for( int i = 0; BacktracePointers[i]; ++i)
     {
         BacktraceNames bn;

stepmania/src/archutils/Unix/CrashHandlerInternal.h

@@ -4,5 +4,7 @@
 #define BACKTRACE_MAX_SIZE 1024
 #define CHILD_MAGIC_PARAMETER "--private-do-crash-handler"
 
+#define BACKTRACE_METHOD_NOT_AVAILABLE ((void*) -1)
+
 #endif