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* how does 0x##p##q work
@ 2015-07-24 16:02 Ahmed Soliman
  2015-07-24 16:58 ` Randy Dunlap
  0 siblings, 1 reply; 2+ messages in thread
From: Ahmed Soliman @ 2015-07-24 16:02 UTC (permalink / raw)
  To: linux-kernel

I was working on cleaning up some files in the crypto dirctory using
checkpatch.pl
and I found this strange define in crypto/gf128mul.c
#define xx(p, q) 0x##p##q
It just seems really weird macro and I cant figure out what is it
supposed to do!!

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: how does 0x##p##q work
  2015-07-24 16:02 how does 0x##p##q work Ahmed Soliman
@ 2015-07-24 16:58 ` Randy Dunlap
  0 siblings, 0 replies; 2+ messages in thread
From: Randy Dunlap @ 2015-07-24 16:58 UTC (permalink / raw)
  To: Ahmed Soliman, linux-kernel

On 07/24/15 09:02, Ahmed Soliman wrote:
> I was working on cleaning up some files in the crypto dirctory using
> checkpatch.pl
> and I found this strange define in crypto/gf128mul.c
> #define xx(p, q) 0x##p##q
> It just seems really weird macro and I cant figure out what is it
> supposed to do!!

## is defined in any complete C language spec (it's a preprocessor directive).

It is used for string concatenation, aka pasting or gluing strings together.

google can find lots of references for it if you need more info.

-- 
~Randy

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2015-07-24 16:02 how does 0x##p##q work Ahmed Soliman
2015-07-24 16:58 ` Randy Dunlap

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