Re: [Qemu-devel] Re: Porting QEMU to new hosts with unusual ABI (sizeof(long) != sizeof(void *))

[Stefan Weil <weil@mail.berlios.de>]

Am 07.02.2011 08:23, schrieb Markus Armbruster:
> Stefan Weil <weil@mail.berlios.de> writes:
>> Am 05.02.2011 16:35, schrieb Blue Swirl:
> [...]
>>> The patch changes also signed longs to uintptr_t. That could introduce
>>> regressions, so please use signed/unsigned as original.
>>
>> I changed the code manually, and there was only one location where
>> signed/unsigned made a difference. That single case was an int
>> parameter passed in a void pointer, and I used intptr_t there.
>>
>> I had the impression that in the current code (long) was
>> sometimes used because it is shorter than (unsigned long) :-)
>>
>> As long as changes are made manually with the necessary care,
>> I'd recommend using uintptr_t where possible.
>
> I'd recommend not to mix up the intptr portability clean up with the
> signedness cleanup. Much easier to review separately. Moreover,
> cleaning up signedness changes generated code, while cleaning up the
> types shouldn't (except on hosts where the code doesn't work).
> Testable, just don't forget to strip the debug info.
>
> [...]



Markus, your recommendation is ok for modifications which change the
generated code or which need more context for the review.

I don't think that you will have any problem with reviewing
"signedness changes" like these ones:

-#define saddr(x) (uint8_t *)(long)(x)
-#define laddr(x) (uint8_t *)(long)(x)
+#define saddr(x) (uint8_t *)(uintptr_t)(x)
+#define laddr(x) (uint8_t *)(uintptr_t)(x)

Neither of these changes changes the binary code for the commonly used 
hosts,
and the patch does not need further context for the review.

I intend to split my patch in three parts:

* one for tcg_gen_exit_tb calls which will be modified as Blue Swirl has 
suggested
* one for the parameter passing of a signed value via pointer
* one for the rest which contains only a handful of trivial "signedness 
changes",
   all following the same pattern like the example given above

Is that ok?

Regards,
Stefan