Register Variables in c

Register Variables in c

[Ali Abdul Ghani]

hi list
I have a question
I read about register variables
gcc Support register variables??

or treat him like any other variable??

Re: Register Variables in c

[Tim Prince]

On 9/18/2014 5:15 AM, Ali Abdul Ghani wrote:
> I have a question
> I read about register variables
> gcc Support register variables??
>
> or treat him like any other variable??
This is covered in reasonable detail in online docs, e.g.
https://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html

As you're probably aware, the primary portable purpose of "register" is 
to prevent taking the address.

Re: Register Variables in c

[Ian Lance Taylor]

On Thu, Sep 18, 2014 at 2:15 AM, Ali Abdul Ghani <blade.vp2020@gmail.com> wrote:
>
> I have a question
> I read about register variables
> gcc Support register variables??
>
> or treat him like any other variable??

In GCC the only meanings of the register qualifier are that you can't
the address of a register variable, and as a GCC extension you can
declare the specific register that the variable should go into.

Ian

Re: Register Variables in c

[David Brown]

On 19/09/14 00:56, Ian Lance Taylor wrote:
> On Thu, Sep 18, 2014 at 2:15 AM, Ali Abdul Ghani <blade.vp2020@gmail.com> wrote:
>>
>> I have a question
>> I read about register variables
>> gcc Support register variables??
>>
>> or treat him like any other variable??
> 
> In GCC the only meanings of the register qualifier are that you can't
> the address of a register variable, and as a GCC extension you can
> declare the specific register that the variable should go into.
> 

I believe the register qualifier is used as a hint when you compile
without optimisation, and will encourage the compiler to put the
variable in a register rather than on the stack.  The hint is ignored
when optimising - they are treated as any other variable (other than
making it illegal to take an address), as the compiler will do a better
job of allocating variables to registers than a human would.

David

Re: Register Variables in c

[Kayven Riese]

On 9/18/14, Ali Abdul Ghani <blade.vp2020@gmail.com> wrote:
> hi list
> I have a question
> I read about register variables
> gcc Support register variables??
>
> or treat him like any other variable??
>
you have TO use inline assembly code. it has to bedone in assembly
language which will be machine specific. try googling using assembly
language in C. I am working on a flip phone here.

-- 
  Sincerely,

  Kayven Riese
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  Kayven Riese, MSCS,
                      MS  (Physiology and Biophysics)
  (415) 902 5513 cellular
  http://kayve.net
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