Re: [PATCH-for-9.1 05/21] cpus: Open code OBJECT_DECLARE_TYPE() in OBJECT_DECLARE_CPU_TYPE()

[Zhao Liu]

Hi Philippe,

On Fri, Mar 15, 2024 at 02:08:53PM +0100, Philippe Mathieu-Daudé wrote:
> Date: Fri, 15 Mar 2024 14:08:53 +0100
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Subject: [PATCH-for-9.1 05/21] cpus: Open code OBJECT_DECLARE_TYPE() in
>  OBJECT_DECLARE_CPU_TYPE()
> X-Mailer: git-send-email 2.41.0
> 
> Since the OBJECT_DECLARE_CPU_TYPE() macro uses the abstract ArchCPU
> type, when declaring multiple CPUs of the same ArchCPU type we get
> an error related to the indirect G_DEFINE_AUTOPTR_CLEANUP_FUNC()
> use within OBJECT_DECLARE_TYPE():
> 
>   target/mips/cpu-qom.h:31:1: error: redefinition of 
> 'glib_autoptr_clear_ArchCPU'
>   OBJECT_DECLARE_CPU_TYPE(MIPS64CPU, MIPSCPUClass, MIPS64_CPU)
>   ^
>   include/hw/core/cpu.h:82:5: note: expanded from macro 
> 'OBJECT_DECLARE_CPU_TYPE'
>       OBJECT_DECLARE_TYPE(ArchCPU, CpuClassType, CPU_MODULE_OBJ_NAME);
>       ^
>   include/qom/object.h:237:5: note: expanded from macro 'OBJECT_DECLARE_TYPE'
>       G_DEFINE_AUTOPTR_CLEANUP_FUNC(InstanceType, object_unref) \
>       ^
>   /usr/include/glib-2.0/glib/gmacros.h:1371:3: note: expanded from macro 
> 'G_DEFINE_AUTOPTR_CLEANUP_FUNC'
>     _GLIB_DEFINE_AUTOPTR_CLEANUP_FUNCS(TypeName, TypeName, func)
>     ^
>   /usr/include/glib-2.0/glib/gmacros.h:1354:36: note: expanded from macro 
> '_GLIB_DEFINE_AUTOPTR_CLEANUP_FUNCS'
>     static G_GNUC_UNUSED inline void _GLIB_AUTOPTR_CLEAR_FUNC_NAME(TypeName) 
> (TypeName *_ptr)                     \
>                                      ^
>   /usr/include/glib-2.0/glib/gmacros.h:1338:49: note: expanded from macro 
> '_GLIB_AUTOPTR_CLEAR_FUNC_NAME'
>   #define _GLIB_AUTOPTR_CLEAR_FUNC_NAME(TypeName) 
> glib_autoptr_clear_##TypeName
>                                                   ^
>   <scratch space>:54:1: note: expanded from here
>   glib_autoptr_clear_ArchCPU
>   ^
>   target/mips/cpu-qom.h:30:1: note: previous definition is here
>   OBJECT_DECLARE_CPU_TYPE(MIPS32CPU, MIPSCPUClass, MIPS32_CPU)
>   ^
> 
> Avoid that problem by expanding the OBJECT_DECLARE_TYPE() macro
> within OBJECT_DECLARE_CPU_TYPE().
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Acked-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> TODO: check rth comment:
> What about adding an OBJECT_DECLARE_CPU_SUBTYPE that omits half the stuff 
> instead?
> We don't need another object typedef at all, for instance.
> ---
>  include/hw/core/cpu.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index ec14f74ce5..4c2e5095bf 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -78,7 +78,12 @@ DECLARE_CLASS_CHECKERS(CPUClass, CPU,
>   */
>  #define OBJECT_DECLARE_CPU_TYPE(CpuInstanceType, CpuClassType, 
> CPU_MODULE_OBJ_NAME) \
>      typedef struct ArchCPU CpuInstanceType; \
> -    OBJECT_DECLARE_TYPE(ArchCPU, CpuClassType, CPU_MODULE_OBJ_NAME);
> +    typedef struct CpuClassType CpuClassType; \
> +    \
> +    G_DEFINE_AUTOPTR_CLEANUP_FUNC(CpuInstanceType, object_unref) \
> +    \
> +    DECLARE_OBJ_CHECKERS(CpuInstanceType, CpuClassType, \
> +                         CPU_MODULE_OBJ_NAME, TYPE_##CPU_MODULE_OBJ_NAME)
>

The OBJECT_DECLARE_TYPE is expaneded as the following:

#define OBJECT_DECLARE_TYPE(InstanceType, ClassType, MODULE_OBJ_NAME) \
    typedef struct InstanceType InstanceType; \
    typedef struct ClassType ClassType; \
    \
    G_DEFINE_AUTOPTR_CLEANUP_FUNC(InstanceType, object_unref) \
    \
    DECLARE_OBJ_CHECKERS(InstanceType, ClassType, \
                         MODULE_OBJ_NAME, TYPE_##MODULE_OBJ_NAME)

So the above code change deletes a typedef:

    typedef struct ArchCPU ArchCPU;

Will this deletion break the direct uses of ArchCPU? e.g., in
accel/tcg/translator.c:

static void set_can_do_io(DisasContextBase *db, bool val)
{
    if (db->saved_can_do_io != val) {
        ...
        tcg_gen_st8_i32(tcg_constant_i32(val), tcg_env,
                        offsetof(ArchCPU, parent_obj.neg.can_do_io) -
                        offsetof(ArchCPU, env));
    }
}

Thanks,
Zhao