Re: [PATCH v4 07/43] tcg: Add in_code_gen_buffer

[Philippe Mathieu-Daudé]

On 12/15/20 11:43 PM, Richard Henderson wrote:
> On 12/14/20 4:09 PM, Philippe Mathieu-Daudé wrote:
>> On 12/14/20 3:02 PM, Richard Henderson wrote:
>>> Create a function to determine if a pointer is within the buffer.
>>>
>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>>  include/tcg/tcg.h         |  6 ++++++
>>>  accel/tcg/translate-all.c | 26 ++++++++------------------
>>>  2 files changed, 14 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
>>> index bb1e97b13b..e4d0ace44b 100644
>>> --- a/include/tcg/tcg.h
>>> +++ b/include/tcg/tcg.h
>>> @@ -680,6 +680,12 @@ extern __thread TCGContext *tcg_ctx;
>>>  extern void *tcg_code_gen_epilogue;
>>>  extern TCGv_env cpu_env;
>>>  
>>> +static inline bool in_code_gen_buffer(const void *p)
>>> +{
>>> +    const TCGContext *s = &tcg_init_ctx;
>>> +    return (size_t)(p - s->code_gen_buffer) <= s->code_gen_buffer_size;
>>
>> If 'p == s->code_gen_buffer + s->code_gen_buffer_size',
>> is it really "in" the buffer?
> 
> Well, sort of.
> 
> Compare the fact that in C, a pointer to the end of an array is valid as a
> pointer even though it can't be dereferenced.  This is a pointer to the end of
> the buffer.
> 
> Extra commentary required?

Preferably, since you change from '<' to '<=', this would
make it clearer, then no question asked :)

With it:
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Thanks,

Phil.