libqtest: Add qtest_[v]startf()

We have several callers that were formatting the argument strings
themselves; consolidate this effort by adding new convenience
functions directly in libqtest, and update some call-sites that
can benefit from it.

Note that the new functions qtest_startf() and qtest_vstartf()
behave more like qtest_init() (the caller must assign global_qtest
after the fact, rather than getting it implicitly set).  This helps
us prepare for future patches that get rid of the global variable,
by explicitly highlighting which tests still depend on it now.

Signed-off-by: Eric Blake <eblake@redhat.com>
[thuth: Dropped the hunks that do not apply cleanly to qemu master
 yet and added the missing g_free(args) in qtest_vstartf()]
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1508336428-20511-2-git-send-email-thuth@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/tests/boot-serial-test.c b/tests/boot-serial-test.c
index b95c5e7..c935d69 100644
--- a/tests/boot-serial-test.c
+++ b/tests/boot-serial-test.c
@@ -71,7 +71,6 @@ done:
 static void test_machine(const void *data)
 {
     const testdef_t *test = data;
-    char *args;
     char tmpname[] = "/tmp/qtest-boot-serial-XXXXXX";
     int fd;
 
@@ -82,18 +81,15 @@ static void test_machine(const void *data)
      * Make sure that this test uses tcg if available: It is used as a
      * fast-enough smoketest for that.
      */
-    args = g_strdup_printf("-M %s,accel=tcg:kvm "
-                           "-chardev file,id=serial0,path=%s "
-                           "-no-shutdown -serial chardev:serial0 %s",
-                           test->machine, tmpname, test->extra);
-
-    qtest_start(args);
+    global_qtest = qtest_startf("-M %s,accel=tcg:kvm "
+                                "-chardev file,id=serial0,path=%s "
+                                "-no-shutdown -serial chardev:serial0 %s",
+                                test->machine, tmpname, test->extra);
     unlink(tmpname);
 
     check_guest_output(test, fd);
     qtest_quit(global_qtest);
 
-    g_free(args);
     close(fd);
 }