linux-kernel - Re: Userspace compiler support of "long long"

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Date:	Wed, 27 Jun 2007 16:16:48 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Kyle Moffett <mrmacman_g4@....com>
Cc:	Adrian Bunk <bunk@...sta.de>,
	LKML Kernel <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>, david@...g.hm,
	linux-arch@...r.kernel.org
Subject: Re: Userspace compiler support of "long long"

On Wed, 27 Jun 2007 15:57:15 -0700 Randy Dunlap wrote:

> On Wed, 27 Jun 2007 18:30:52 -0400 Kyle Moffett wrote:
> 
> > On Jun 27, 2007, at 13:32:40, Adrian Bunk wrote:
> > > AFAIR the Intel compiler claims to be gcc.
> > >
> > > But these are by far not the only C compilers under Linux, and the  
> > > more important points are:
> > >
> > > Is there any userspace Linux compiler that does not support "long  
> > > long"?
> > 
> > Don't know, but I'd guess not.
> > 
> > 
> > > If yes, is there any other way to tell that something is a 64bit  
> > > int on 32bit architectures?
> > 
> > Not that I know of.  Probably the straight #else conditional is OK.   
> > We should also merge up the types since *EVERY* linux architecture  
> > has these same types:
> > 
> > typedef   signed char      __s8;
> > typedef unsigned char      __u8;
> > typedef   signed short     __s16;
> > typedef unsigned short     __u16;
> > typedef   signed int       __s32;
> > typedef unsigned int       __u32;
> > 
> > Then all 64-bit archs have:
> > typedef   signed long      __s64;
> > typedef unsigned long      __u64;
> > 
> > While all 32-bit archs have:
> > typedef   signed long long __s64;
> > typedef unsigned long long __u64;
> > 
> > The only trick is if you care about building 32-bit compat code using  
> > 64-bit linux kernel headers.  In that case we should probably just  
> > make all archs use "long long" for their 64-bit integers, unless  
> > there's some platform I'm not remembering where "long long" is 128- 
> > bits or bigger.  The other benefit is that people could then just use  
> > the printf format "%llu" for 64-bit integers instead of having to  
> > conditionalize it all over the place.
> > 
> > I'm working on a patch now.
> 
> LDD3 ch. 11 says that long on Sparc64 is 32 bits.
> Same for "ppc" (don't know which power* arch. they mean by that).

Hm, I suppose that table only applies to userspace, not kernel...

---
~Randy
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