Hi,

I'm asking a pretty amateur question.

I've come accross code like this huge number of times in the kernel:

#define __set_task_state(tsk, state_value) \
do { (tsk)->state = (state_value); } while (0)

What is the reason to use do while loop if it is only meant to be
executed just once? Why not a simple:

#define __set_task_state(tsk, state_value) \
{ (tsk)->state = (state_value); }

TIA,

Rajat
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> What is the reason to use do while loop if it is only meant to be
> executed just once? Why not a simple:

look at kernelnewbies faq/google/search the archives for this list.

anupam

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On 15/05/06, Rajat Jain <rajat.noida.india [at] gmail.com> wrote:
> Hi,
>
> I'm asking a pretty amateur question.
>
> I've come accross code like this huge number of times in the kernel:
>
> #define __set_task_state(tsk, state_value) \
> do { (tsk)->state = (state_value); } while (0)
>
> What is the reason to use do while loop if it is only meant to be
> executed just once? Why not a simple:
>
> #define __set_task_state(tsk, state_value) \
> { (tsk)->state = (state_value); }
>

http://www.kernelnewbies.org/FAQ/DoWhile0

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On 5/15/06, Rajat Jain <rajat.noida.india [at] gmail.com> wrote:
>
> Hi,
>
> I'm asking a pretty amateur question.
>
> I've come accross code like this huge number of times in the kernel:
>
> #define __set_task_state(tsk, state_value) \
> do { (tsk)->state =3D (state_value); } while (0)
>
> What is the reason to use do while loop if it is only meant to be
> executed just once? Why not a simple:
>
> #define __set_task_state(tsk, state_value) \
> { (tsk)->state =3D (state_value); }
>
> TIA,
>
> Rajat
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
>
See this
http://kernelnewbies.org/FAQ/DoWhile0

Rgds,
Adil

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<br><br>
<div><span class=3D"gmail_quote">On 5/15/06, <b class=3D"gmail_sendername">=
Rajat Jain</b> <<a href=3D"mailto:rajat.noida.india [at] gmail.com">rajat.noi=
da.india [at] gmail.com</a>> wrote:</span>
<blockquote class=3D"gmail_quote" style=3D"PADDING-LEFT: 1ex; MARGIN: 0px 0=
px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Hi,<br><br>I'm asking a pretty a=
mateur question.<br><br>I've come accross code like this huge number of tim=
es in the kernel:
<br><br>#define __set_task_state(tsk, state_value)    &=
nbsp;         \<br>  =
;     do { (tsk)->state =3D (state_value); } while (=
0)<br><br>What is the reason to use do while loop if it is only meant to be=
<br>executed just once? Why not a simple:
<br><br>#define __set_task_state(tsk, state_value)    &=
nbsp;         \<br>  =
;     { (tsk)->state =3D (state_value); }<br><br>TIA=
,<br><br>Rajat<br><br>--<br>Kernelnewbies: Help each other learn about the =
Linux kernel.<br>Archive:      
<a href=3D"http://mail.nl.linux.org/kernelnewbies/">http://mail.nl.linux.or=
g/kernelnewbies/</a><br>FAQ:        =
;   <a href=3D"http://kernelnewbies.org/faq/">http://kernelnewbie=
s.org/faq/</a><br><br></blockquote></div>
<div><br>See this</div>
<div><a href=3D"http://kernelnewbies.org/FAQ/DoWhile0">http://kernelnewbies=
..org/FAQ/DoWhile0</a></div>
<div> </div>
<div>Rgds,</div>
<div>Adil</div>

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Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/