From: Gavin Shan <gshan@redhat.com>

It's no sense to check the CPU type when mc->valid_cpu_types[0] is
NULL, which is a program error. Raise an assert on this.

A precise hint for the error message is given when mc->valid_cpu_types[0]
is the only valid entry. Besides, enumeration on mc->valid_cpu_types[0]
when we have mutiple valid entries there is avoided to increase the code
readability, as suggested by Philippe Mathieu-Daudé.

Besides, @cc comes from machine->cpu_type or mc->default_cpu_type. For
the later case, it can be NULL and it's also a program error. We should
use assert() in this case.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Message-ID: <20231204004726.483558-4-gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/core/machine.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 0119b11fc8..c523ce32eb 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1412,6 +1412,7 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
      * type is provided through '-cpu' option.
      */
     if (mc->valid_cpu_types) {
+        assert(mc->valid_cpu_types[0] != NULL);
         for (i = 0; mc->valid_cpu_types[i]; i++) {
             if (object_class_dynamic_cast(oc, mc->valid_cpu_types[i])) {
                 break;
@@ -1421,20 +1422,27 @@ static bool is_cpu_type_supported(const MachineState *machine, Error **errp)
         /* The user specified CPU type isn't valid */
         if (!mc->valid_cpu_types[i]) {
             error_setg(errp, "Invalid CPU type: %s", machine->cpu_type);
-            error_append_hint(errp, "The valid types are: %s",
-                              mc->valid_cpu_types[0]);
-            for (i = 1; mc->valid_cpu_types[i]; i++) {
-                error_append_hint(errp, ", %s", mc->valid_cpu_types[i]);
+            if (!mc->valid_cpu_types[1]) {
+                error_append_hint(errp, "The only valid type is: %s\n",
+                                  mc->valid_cpu_types[0]);
+            } else {
+                error_append_hint(errp, "The valid types are: ");
+                for (i = 0; mc->valid_cpu_types[i]; i++) {
+                    error_append_hint(errp, "%s%s",
+                                      mc->valid_cpu_types[i],
+                                      mc->valid_cpu_types[i + 1] ? ", " : "");
+                }
+                error_append_hint(errp, "\n");
             }
 
-            error_append_hint(errp, "\n");
             return false;
         }
     }
 
     /* Check if CPU type is deprecated and warn if so */
     cc = CPU_CLASS(oc);
-    if (cc && cc->deprecation_note) {
+    assert(cc != NULL);
+    if (cc->deprecation_note) {
         warn_report("CPU model %s is deprecated -- %s",
                     machine->cpu_type, cc->deprecation_note);
     }
-- 
2.41.0