Re: [Qemu-devel] [PATCH v2 03/26] armv7m: Explicit error for bad vector table

[Peter Maydell]

On 27 December 2015 at 20:43, Michael Davidsaver <address@hidden> wrote:
> On 12/17/2015 08:25 AM, Peter Maydell wrote:
>> On 3 December 2015 at 00:18, Michael Davidsaver <address@hidden> wrote:
>>> ...
>>> +static
>>> +uint32_t arm_v7m_load_vector(ARMCPU *cpu)
>>> +
>>> +{
>>> +    CPUState *cs = &cpu->parent_obj;
>> This isn't the right way to cast to the base class of a QOM object.
>> You want:
>>    CPUState *cs = CPU(cpu);
>
> from cpu.h
>
>> /* Since this macro is used a lot in hot code paths and in conjunction
>> with
>>  * FooCPU *foo_env_get_cpu(), we deviate from usual QOM practice by using
>>  * an unchecked cast.
>>  */
>> #define CPU(obj) ((CPUState *)(obj))
>
> Given the present definition of CPU() this change seems like a step
> backwards in terms of safety as mis-use won't be caught at compile or
> runtime.  I'll change it anyway.

The idea is that all code should use the QOM cast macros.
At the moment we have a special case for CPU() because it's
a hot path; in future we might be able to improve the speed of
the cast checking to the point where we can reinstate it.

thanks
-- PMM