Re: [PATCH] gdb/i387-tdep.c: Avoid warning for "-Werror=strict-overflow"

[Chen Gang <gang.chen.5i5j@gmail.com>]

On 10/6/14 16:41, Pedro Alves wrote:
> On 10/04/2014 06:18 AM, Chen Gang wrote:
>>
>> OK, thanks. It is really one way, it is a little better than my original
>> way. But for me, it is still not a good idea: it introduces a new macro
>> and a new variable for each area (originally, it is only one statement).
> 
> I see no problem with adding the new macro.  We already have a ton
> of similar macros, see i386-tdep.h and i387-tdep.h.  Looks
> like the existing I387_NUM_REGS is what we'd need here?
> 
> BTC, OOC, did you try Joel's idea with the local variable?
> In case Mark prefers that, it'd be good to know whether it works.
> I can't seem to get my gcc to emit that warning.
> 
> Combining both ideas, for clarity, we end up with something
> like:
> 
>  int end;
> 
>  end = I387_ST0_REGNUM (tdep) + I387_NUM_REGS;
>  for (i = I387_ST0_REGNUM (tdep); i < end; i++)
> 
>  ...
> 
>  end = I387_XMM0_REGNUM (tdep) + I387_NUM_XMM_REGS (tdep);
>  for (i = I387_XMM0_REGNUM (tdep); i < end; i++)
> 
> 
> That's way clearer to me than the existing:
> 

That's way not quite bad to me than the existing:

 - It is easier understanding, although a little complex than origin.

 - For compiler, 'end' is simple enough to be sure to be optimized.

 - And I guess, compiler will understand, and will not worry about it.


>  for (i = I387_ST0_REGNUM (tdep); i < I387_XMM0_REGNUM (tdep); i++)
> ...
>  for (i = I387_XMM0_REGNUM (tdep); i < I387_MXCSR_REGNUM (tdep); i++)
> 
> anyway, which assumes the reader knows register numbers are
> ordered like st -> xmm -> mxcrsr.
> 
> If this works, I think it's my preference.
> 

OK, thanks, at least, what you said is acceptable to me. If no any
additional reply within this week (within 2014-10-12), I shall send
patch v2 for it.

>> For me, "-Werror" need always be optional, but not mandatory.
> 
> It's mandatory only on development builds.  -Werror is not on by
> default on released GDBs.
> 

OK, thanks.


Thanks.
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed