Re: [Qemu-devel] [PATCH 2/5] CODING_STYLE: add C type rules

[Avi Kivity <avi@redhat.com>]

  On 08/19/2010 11:17 AM, Jes Sorensen wrote:
> On 08/19/10 10:10, Avi Kivity wrote:
>>   On 08/19/2010 10:58 AM, Jes Sorensen wrote:
>>>> In C99, bool is a real type.
>>> Kinda real, I would qualify it more as a pseudo type. It doesn't map to
>>> any register size or even instruction actions.
>> Neither do int, short, long, long long, or signed short long float.
> Well most processors support 32 bit register ops, even when running in
> 64 bit mode.

8-bit processors have 8-bit register size and 16-bit ints.  Some 
processors have 36-bit ints.  If you only code for processors which have 
Linux ports, and for those ports, then everything will be the same.  
Surprise!

> long is the maximum register size in pretty much any sane
> setup,

Not on those 8-bit machines.

> which is why it is such a mess that M$ took the easy way out when
> they picked for win64. Tons of user code will have portability problems
> because of this.

They did that to avoid portability problems, presumably.

>>> Most processors, at least
>>> the ones I have programmed, tend to treat it as zero == false,
>>> everything else == true.
>> Processors don't have _Bool.
> No but something has to generate code to handle it.

gcc

>>> For structure packing it's ugly.
>> Use uint*_t for externally visible structures.  use _Bool for internal
>> booleans.
> Structure packing is more than passing structures to external processes
> or saving them, it's also cache line alignment. In your case we should
> change pretty much any data structure in QEMU that is in a critical data
> path to use *int*_t.

Not at all, _Bool is smaller or equal to int and thus can only improve 
packing.

If you want to align explicitly, use alignment attributes.

-- 
error compiling committee.c: too many arguments to function