[PATCH kvm-unit-tests] scripts/mkstandalone: fix races on forced exits

["Radim Krčmář" <rkrcmar@redhat.com>]

There are two bugs that happen if we exit after the first line of
following examples,

1) var=`mktemp`
   # we don't remove the temp file
   trap 'rm -f $var' EXIT

2) trap 'rm -f $cfg' EXIT
   # if $cfg is defined (= exported), we delete an unrelated file
   cfg=`mktemp`

Unit tests don't use cleanup variable anymore, but redefine EXIT trap
every time a new file is added.  This makes the standalone test slower,
but both scripts are less tangled now, IMO.  (Passing temp_file_vars as
an argument is nicer in theory, but doesn't look very good.)

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 I wanted to redefine the trap from the beginning, but it didn't pass
 sanity test before ... and Paolo also noticed a severe bug in the
 original series, so I probably wasn't testing in the right directory
 on both occasions :/

 scripts/mkstandalone.sh | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/scripts/mkstandalone.sh b/scripts/mkstandalone.sh
index 58910059a355..7d3455e66c99 100755
--- a/scripts/mkstandalone.sh
+++ b/scripts/mkstandalone.sh
@@ -19,8 +19,11 @@ temp_file ()
 	local var="$1"
 	local file="$2"
 
+	temp_file_vars+=" \$$var"
+
+	echo "unset $var"
+	echo "trap 'rm -f $temp_file_vars' EXIT"
 	echo "$var=\`mktemp\`"
-	echo "cleanup=\"\$$var \$cleanup\""
 	echo "base64 -d << 'BIN_EOF' | zcat > \$$var || exit 1"
 
 	gzip - < $file | base64
@@ -32,6 +35,7 @@ temp_file ()
 generate_test ()
 {
 	local args=( $(escape "${@}") )
+	local temp_file_vars
 
 	echo "#!/bin/bash"
 	grep '^ARCH=' config.mak
@@ -42,8 +46,6 @@ generate_test ()
 		return 1
 	fi
 
-	echo "trap 'rm -f \$cleanup' EXIT"
-
 	temp_file bin "$kernel"
 	args[3]='$bin'
 
@@ -76,6 +78,7 @@ function mkstandalone()
 	return 0
 }
 
+unset cfg
 trap 'rm -f $cfg' EXIT
 cfg=$(mktemp)
 
-- 
2.7.0