system/vl.c: Print machine name, not "(null)", for unknown machine types

In commit 412d294ffdc we tried to improve the error message printed when
the machine type is unknown, but we used the wrong variable, resulting in:

$ ./build/x86/qemu-system-aarch64 -M bang
qemu-system-aarch64: unsupported machine type: "(null)"
Use -machine help to list supported machines

Use the right variable, so we produce more helpful output:

$ ./build/x86/qemu-system-aarch64 -M bang
qemu-system-aarch64: unsupported machine type: "bang"
Use -machine help to list supported machines

Note that we must move the qdict_del() to below the error_setg(),
because machine_type points into the value of that qdict entry,
and deleting it will make the pointer invalid.

Cc: qemu-stable@nongnu.org
Fixes: 412d294ffdc ("vl.c: select_machine(): add selected machine type to error message")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/system/vl.c b/system/vl.c
index 41d53d2456affb3ead07c2a73901ff6ff5db4f38..01b8b8e77ad1d12dca3d4a4dd664871e14d13c59 100644 (file)
--- a/system/vl.c
+++ b/system/vl.c
@@ -1679,10 +1679,10 @@ static MachineClass *select_machine(QDict *qdict, Error **errp)
 
     if (machine_type) {
         machine_class = find_machine(machine_type, machines);
-        qdict_del(qdict, "type");
         if (!machine_class) {
-            error_setg(errp, "unsupported machine type: \"%s\"", optarg);
+            error_setg(errp, "unsupported machine type: \"%s\"", machine_type);
         }
+        qdict_del(qdict, "type");
     } else {
         machine_class = find_default_machine(machines);
         if (!machine_class) {