[v1] vl: Abort if multiple machines are registered as default

[PATCH] vl: Abort if multiple machines are registered as default

Posted by Philippe Mathieu-Daudé 5 years, 9 months ago

It would be confusing to have multiple default machines.
Abort if this ever occurs.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 vl.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/vl.c b/vl.c
index 7dcb0879c4..da828188eb 100644
--- a/vl.c
+++ b/vl.c
@@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
     GSList *el;
 
     if (is_help_option(name)) {
+        int default_count = 0;
+
         printf("Supported machines are:\n");
         machines = g_slist_sort(machines, machine_class_cmp);
         for (el = machines; el; el = el->next) {
@@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
             printf("%-20s %s%s%s\n", mc->name, mc->desc,
                    mc->is_default ? " (default)" : "",
                    mc->deprecation_reason ? " (deprecated)" : "");
+            default_count += !!mc->is_default;
+        }
+        if (default_count > 1) {
+            error_printf("Multiple default machines available\n");
+            abort();
         }
         exit(0);
     }
-- 
2.21.1

Re: [PATCH] vl: Abort if multiple machines are registered as default

Posted by Marc-André Lureau 5 years, 9 months ago

Hi

On Fri, Feb 7, 2020 at 12:03 PM Philippe Mathieu-Daudé
<philmd@redhat.com> wrote:
>
> It would be confusing to have multiple default machines.
> Abort if this ever occurs.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  vl.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/vl.c b/vl.c
> index 7dcb0879c4..da828188eb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>      GSList *el;
>
>      if (is_help_option(name)) {
> +        int default_count = 0;
> +
>          printf("Supported machines are:\n");
>          machines = g_slist_sort(machines, machine_class_cmp);
>          for (el = machines; el; el = el->next) {
> @@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>              printf("%-20s %s%s%s\n", mc->name, mc->desc,
>                     mc->is_default ? " (default)" : "",
>                     mc->deprecation_reason ? " (deprecated)" : "");
> +            default_count += !!mc->is_default;
> +        }
> +        if (default_count > 1) {
> +            error_printf("Multiple default machines available\n");
> +            abort();

looks ok

It's a build-time issue? If the user can't do anything about it, you
may simply have an assert(default_count <= 1) rather than a
human-friendly string, I think.

-- 
Marc-André Lureau

Re: [PATCH] vl: Abort if multiple machines are registered as default

Posted by Laurent Vivier 5 years, 9 months ago

Le 07/02/2020 à 12:02, Philippe Mathieu-Daudé a écrit :
> It would be confusing to have multiple default machines.
> Abort if this ever occurs.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  vl.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/vl.c b/vl.c
> index 7dcb0879c4..da828188eb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>      GSList *el;
>  
>      if (is_help_option(name)) {
> +        int default_count = 0;
> +
>          printf("Supported machines are:\n");
>          machines = g_slist_sort(machines, machine_class_cmp);
>          for (el = machines; el; el = el->next) {
> @@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>              printf("%-20s %s%s%s\n", mc->name, mc->desc,
>                     mc->is_default ? " (default)" : "",
>                     mc->deprecation_reason ? " (deprecated)" : "");
> +            default_count += !!mc->is_default;
> +        }
> +        if (default_count > 1) {
> +            error_printf("Multiple default machines available\n");
> +            abort();
>          }
>          exit(0);
>      }
> 

Does it really deserve an abort?
Ideal solution would be to be able to check this at build or in the unit
tests.

Thanks,
Laurent

Re: [PATCH] vl: Abort if multiple machines are registered as default

Posted by Philippe Mathieu-Daudé 5 years, 9 months ago

On 2/7/20 12:08 PM, Laurent Vivier wrote:
> Le 07/02/2020 à 12:02, Philippe Mathieu-Daudé a écrit :
>> It would be confusing to have multiple default machines.
>> Abort if this ever occurs.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>>   vl.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/vl.c b/vl.c
>> index 7dcb0879c4..da828188eb 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>>       GSList *el;
>>   
>>       if (is_help_option(name)) {
>> +        int default_count = 0;
>> +
>>           printf("Supported machines are:\n");
>>           machines = g_slist_sort(machines, machine_class_cmp);
>>           for (el = machines; el; el = el->next) {
>> @@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char *name, GSList *machines)
>>               printf("%-20s %s%s%s\n", mc->name, mc->desc,
>>                      mc->is_default ? " (default)" : "",
>>                      mc->deprecation_reason ? " (deprecated)" : "");
>> +            default_count += !!mc->is_default;
>> +        }
>> +        if (default_count > 1) {
>> +            error_printf("Multiple default machines available\n");
>> +            abort();
>>           }
>>           exit(0);
>>       }
>>
> 
> Does it really deserve an abort?
> Ideal solution would be to be able to check this at build or in the unit
> tests.

This is for developers, not for users. I'll use Marc-André suggestion 
and use an assertion.

Re: [PATCH] vl: Abort if multiple machines are registered as default

Posted by Laurent Vivier 5 years, 9 months ago

Le 07/02/2020 à 12:25, Philippe Mathieu-Daudé a écrit :
> On 2/7/20 12:08 PM, Laurent Vivier wrote:
>> Le 07/02/2020 à 12:02, Philippe Mathieu-Daudé a écrit :
>>> It would be confusing to have multiple default machines.
>>> Abort if this ever occurs.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>>   vl.c | 7 +++++++
>>>   1 file changed, 7 insertions(+)
>>>
>>> diff --git a/vl.c b/vl.c
>>> index 7dcb0879c4..da828188eb 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char
>>> *name, GSList *machines)
>>>       GSList *el;
>>>         if (is_help_option(name)) {
>>> +        int default_count = 0;
>>> +
>>>           printf("Supported machines are:\n");
>>>           machines = g_slist_sort(machines, machine_class_cmp);
>>>           for (el = machines; el; el = el->next) {
>>> @@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char
>>> *name, GSList *machines)
>>>               printf("%-20s %s%s%s\n", mc->name, mc->desc,
>>>                      mc->is_default ? " (default)" : "",
>>>                      mc->deprecation_reason ? " (deprecated)" : "");
>>> +            default_count += !!mc->is_default;
>>> +        }
>>> +        if (default_count > 1) {
>>> +            error_printf("Multiple default machines available\n");
>>> +            abort();
>>>           }
>>>           exit(0);
>>>       }
>>>
>>
>> Does it really deserve an abort?
>> Ideal solution would be to be able to check this at build or in the unit
>> tests.
> 
> This is for developers, not for users. I'll use Marc-André suggestion
> and use an assertion.

I agree, but it's why it would be better if it is detected before it
comes to the user.

Perhaps you can add a test to run "qemu -h" to trigger the abort() early
in the develompment process (if it doesn't already exist).

Thanks,
Laurent
Thanks,
LAurent

Re: [PATCH] vl: Abort if multiple machines are registered as default

Posted by Laurent Vivier 5 years, 9 months ago

Le 07/02/2020 à 12:28, Laurent Vivier a écrit :
> Le 07/02/2020 à 12:25, Philippe Mathieu-Daudé a écrit :
>> On 2/7/20 12:08 PM, Laurent Vivier wrote:
>>> Le 07/02/2020 à 12:02, Philippe Mathieu-Daudé a écrit :
>>>> It would be confusing to have multiple default machines.
>>>> Abort if this ever occurs.
>>>>
>>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>> ---
>>>>   vl.c | 7 +++++++
>>>>   1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/vl.c b/vl.c
>>>> index 7dcb0879c4..da828188eb 100644
>>>> --- a/vl.c
>>>> +++ b/vl.c
>>>> @@ -2354,6 +2354,8 @@ static MachineClass *machine_parse(const char
>>>> *name, GSList *machines)
>>>>       GSList *el;
>>>>         if (is_help_option(name)) {
>>>> +        int default_count = 0;
>>>> +
>>>>           printf("Supported machines are:\n");
>>>>           machines = g_slist_sort(machines, machine_class_cmp);
>>>>           for (el = machines; el; el = el->next) {
>>>> @@ -2364,6 +2366,11 @@ static MachineClass *machine_parse(const char
>>>> *name, GSList *machines)
>>>>               printf("%-20s %s%s%s\n", mc->name, mc->desc,
>>>>                      mc->is_default ? " (default)" : "",
>>>>                      mc->deprecation_reason ? " (deprecated)" : "");
>>>> +            default_count += !!mc->is_default;
>>>> +        }
>>>> +        if (default_count > 1) {
>>>> +            error_printf("Multiple default machines available\n");
>>>> +            abort();
>>>>           }
>>>>           exit(0);
>>>>       }
>>>>
>>>
>>> Does it really deserve an abort?
>>> Ideal solution would be to be able to check this at build or in the unit
>>> tests.
>>
>> This is for developers, not for users. I'll use Marc-André suggestion
>> and use an assertion.
> 
> I agree, but it's why it would be better if it is detected before it
> comes to the user.
> 
> Perhaps you can add a test to run "qemu -h" to trigger the abort() early
> in the develompment process (if it doesn't already exist).

I mean "-M help".

Thanks,
Laurent