testsuite: Flush stdout buffers in InitEventLogging

Otherwise we are sensitive to libc's buffering strategy.
Similar to the issue fixed in 543dfaab166c81f46ac4af76918ce32190aaab22.

3 files changed, 7 insertions, 2 deletions

diff --git a/testsuite/tests/rts/InitEventLogging.hs b/testsuite/tests/rts/InitEventLogging.hs
index 1ec1e65028..83d49d20cc 100644
--- a/testsuite/tests/rts/InitEventLogging.hs
+++ b/testsuite/tests/rts/InitEventLogging.hs
@@ -1,11 +1,13 @@
 {-# LANGUAGE ForeignFunctionInterface #-}
 
+import System.IO
+
 -- Test that the startEventLog interface works as expected.
 main :: IO ()
 main = do
   putStrLn "Starting eventlog..."
+  hFlush stdout
   c_init_eventlog
-  putStrLn "done"
 
 foreign import ccall unsafe "init_eventlog"
   c_init_eventlog :: IO ()
diff --git a/testsuite/tests/rts/InitEventLogging.stdout b/testsuite/tests/rts/InitEventLogging.stdout
index 7cbab8fe59..ef5ce6f2d3 100644
--- a/testsuite/tests/rts/InitEventLogging.stdout
+++ b/testsuite/tests/rts/InitEventLogging.stdout
@@ -1,5 +1,4 @@
 Starting eventlog...
-done
 init
 write
 write
diff --git a/testsuite/tests/rts/InitEventLogging_c.c b/testsuite/tests/rts/InitEventLogging_c.c
index 47e4520fc4..369a4f010f 100644
--- a/testsuite/tests/rts/InitEventLogging_c.c
+++ b/testsuite/tests/rts/InitEventLogging_c.c
@@ -3,19 +3,23 @@
 
 void test_init(void) {
   printf("init\n");
+  fflush(stdout);
 }
 
 bool test_write(void *eventlog, size_t eventlog_size) {
   printf("write\n");
+  fflush(stdout);
   return true;
 }
 
 void test_flush(void) {
   printf("flush\n");
+  fflush(stdout);
 }
 
 void test_stop(void) {
   printf("stop\n");
+  fflush(stdout);
 }
 
 const EventLogWriter writer = {