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Re: [PATCH] gdb/i387-tdep.c: Avoid warning for "-Werror=strict-overflow"
- From: Pedro Alves <palves at redhat dot com>
- To: Walfred Tedeschi <walfred dot tedeschi at intel dot com>, michael dot sturm at intel dot com
- Cc: Mark Kettenis <mark dot kettenis at xs4all dot nl>, amodra at gmail dot com, gbenson at redhat dot com, binutils at sourceware dot org, gdb-patches at sourceware dot org
- Date: Thu, 09 Oct 2014 12:20:27 +0100
- Subject: Re: [PATCH] gdb/i387-tdep.c: Avoid warning for "-Werror=strict-overflow"
- Authentication-results: sourceware.org; auth=none
- References: <542EC11C dot 3020406 at gmail dot com> <201410031546 dot s93FknOM002165 at glazunov dot sibelius dot xs4all dot nl> <542EC9FC dot 8050107 at gmail dot com> <20141003164420 dot GK6927 at adacore dot com> <542EE1BF dot 7060203 at redhat dot com> <54365E01 dot 6060800 at intel dot com>
On 10/09/2014 11:05 AM, Walfred Tedeschi wrote:
> Am 10/3/2014 7:49 PM, schrieb Pedro Alves:
>> On 10/03/2014 05:44 PM, Joel Brobecker wrote:
>>>>> Sorry, but obfuscating code to make compilers happy is *not* the way to go.
>>>> OK, I can understand, but for me, these is no other better ways for it,
>>>> except let gdb give up "-Werror" (if always need "--disable-werror"
>>>> during "configure").
>>> I have to agree with Mark on this one, the proposed solution looks
>>> awful. There has to be another way. Maybe declaring a local constant
>>> whose value is I387_XMM0_REGNUM (tdep)?
>> Likely, after transformations and intra-procedural analyses, gcc would
>> end up with the same.
>> for (i = I387_ST0_REGNUM (tdep); i < I387_XMM0_REGNUM (tdep); i++)
>> always iterates exactly 16 times, because I387_XMM0_REGNUM
>> is defined like:
>> #define I387_XMM0_REGNUM(tdep) (I387_ST0_REGNUM (tdep) + 16)
>> An alternative I think might work would be to give that magic
>> 16 constant a name, say:
>> #define I387_NUM_ST_REGS 16
>> and then do:
>> for (i = 0; i < i < I387_NUM_ST_REGS; i++)
>> int r = I387_ST0_REGNUM (tdep) + i;
>> ... use 'r' instead of 'i' ...
>> Pedro Alves
> Later on we have introduced the _END macros, as can be seen on i387-tdep.h.
> Creating one or two of them migh be a good idea to homogeinize the way
> we handle the registers.
> This will finally also join together all ideas presented before in only one.
> Using the end will then make
> for (i = I387_ST0_REGNUM (tdep); i < I387_XMM0_REGNUM (tdep); i++)
> to be
> for (i = I387_ST0_REGNUM (tdep); i < I387_STEND_REGNUM (tdep); i++)
> We also define the number of regs for every technology in that file.
I'm imagining I387_STEND_REGNUM to be just one of:
#define I387_STEND_REGNUM(tdep) (I387_ST0_REGNUM (tdep) + 16)
#define I387_STEND_REGNUM(tdep) (I387_ST0_REGNUM (tdep) + I387_NUM_ST_REGS)
Thus exactly the same as I387_XMM0_REGNUM:
#define I387_XMM0_REGNUM(tdep) (I387_ST0_REGNUM (tdep) + 16)
And so it would trigger the same GCC warning.
So we'd still need to do the local variable trick:
end = I387_STEND_REGNUM (tdep);
for (i = I387_ST0_REGNUM (tdep); i < end; i++)