From 0a134c860fc116a3f1eed71fbdcf48b66221b456 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Mon, 4 Oct 2021 13:28:06 -0700
Subject: [PATCH] Fix TestLib::slurp_file() with offset on windows.

3c5b0685b921 used setFilePointer() to set the position of the filehandle, but
passed the wrong filehandle, always leaving the position at 0. Instead of just
fixing that, remove use of setFilePointer(), we have a perl fd at this point,
so we can just use perl's seek().

Additionally, the perl filehandle wasn't closed, just the windows filehandle.

Reviewed-By: Andrew Dunstan <andrew@dunslane.net>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20211003173038.64mmhgxctfqn7wl6@alap3.anarazel.de
Backpatch: 9.6-, like 3c5b0685b921
---
 src/test/perl/TestLib.pm | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/src/test/perl/TestLib.pm b/src/test/perl/TestLib.pm
index a5c7ae7149..1231c10fc3 100644
--- a/src/test/perl/TestLib.pm
+++ b/src/test/perl/TestLib.pm
@@ -96,7 +96,7 @@ BEGIN
 	if ($windows_os)
 	{
 		require Win32API::File;
-		Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle setFilePointer));
+		Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle));
 	}
 }
 
@@ -272,33 +272,33 @@ sub slurp_file
 	my ($filename, $offset) = @_;
 	local $/;
 	my $contents;
+	my $fh;
+
+	# On windows open file using win32 APIs, to allow us to set the
+	# FILE_SHARE_DELETE flag ("d" below), otherwise other accesses to the file
+	# may fail.
 	if ($Config{osname} ne 'MSWin32')
 	{
-		open(my $in, '<', $filename)
+		open($fh, '<', $filename)
 		  or die "could not read \"$filename\": $!";
-		if (defined($offset))
-		{
-			seek($in, $offset, SEEK_SET)
-			  or die "could not seek \"$filename\": $!";
-		}
-		$contents = <$in>;
-		close $in;
 	}
 	else
 	{
 		my $fHandle = createFile($filename, "r", "rwd")
 		  or die "could not open \"$filename\": $^E";
-		OsFHandleOpen(my $fh = IO::Handle->new(), $fHandle, 'r')
+		OsFHandleOpen($fh = IO::Handle->new(), $fHandle, 'r')
 		  or die "could not read \"$filename\": $^E\n";
-		if (defined($offset))
-		{
-			setFilePointer($fh, $offset, qw(FILE_BEGIN))
-			  or die "could not seek \"$filename\": $^E\n";
-		}
-		$contents = <$fh>;
-		CloseHandle($fHandle)
-		  or die "could not close \"$filename\": $^E\n";
 	}
+
+	if (defined($offset))
+	{
+		seek($fh, $offset, SEEK_SET)
+		  or die "could not seek \"$filename\": $!";
+	}
+
+	$contents = <$fh>;
+	close $fh;
+
 	$contents =~ s/\r\n/\n/g if $Config{osname} eq 'msys';
 	return $contents;
 }