To: pgsql-hackers <pgsql-hackers@postgresql.org>
From: Alexander Lakhin <exclusion@gmail.com>
Subject: gcov coverage data not full with immediate stop
Message-ID: <816a4de5-3f15-4d66-1ec1-791cab2ca6df@gmail.com>
Date: Sun, 10 May 2020 19:00:00 +0300
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Hello hackers,

I've found that gcov coverage data miss some information when a postgres
node stopped in 'immediate' mode.
For example, on the master branch:
make coverage-clean; time make check -C src/test/recovery/; make
coverage-html
generates a coverage report with 106193 lines/6318 functions for me
(`make check` takes 1m34s).
But with the attached simple patch I get a coverage report with 106540
lines/6332 functions (and `make check` takes 2m5s).
(IMO, the slowdown of the test is significant.)

So if we want to make the coverage reports more precise, I see the three
ways:
1. Change the stop mode in teardown_node to fast (probably only when
configured with --enable-coverage);
2. Explicitly stop nodes in TAP tests (where it's important) -- seems
too tedious and troublesome;
3. Explicitly call __gcov_flush in SIGQUIT handler (quickdie)?

Best regards,
Alexander

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diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index af13c320e9c..99c1e85e1a3 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -1242,7 +1242,7 @@ sub teardown_node
 {
 	my $self = shift;
 
-	$self->stop('immediate');
+	$self->stop();
 	return;
 }
 

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