In my experience, neither method is very portable. What might be best
is a autoconf test to see which one works for the given compiler and
then do some macro magic to handle both conditions??? i.e.
#ifdef PRAGMA_PACK
#pragma pack(1)
#endif
struct foo {
... stuff ...
... stuff ...
... stuff ...
} ATTRIBUTE_PACKING;
#ifdef PRAGMA_PACK
#pragma pack(0)
#endif
??
Al
On Fri, 2008-07-25 at 09:58 -0400, Filion, Stéphane wrote:
> #pragma pack(1)/#pragma pack() fixed this problem
>
>
> Did I the first person to see this problem?
>
> If we want to fix this problem we will need to change a lot file. I
> "grep" the ipmitool project and I saw 192 occurance of __attribute__
> ((packed))
>
> Do we want to change all of this structures for #pragma
> pack(1)/#pragma pack()?
>
>
> Stéphane Filion, Ing jr. / Jr.
> Eng.
> Concepteur de logiciel
> Software designer
> [EMAIL PROTECTED]
> Kontron Canada
> www.kontron.com
> Tel.: (450) 437-4661 ext: 2459
> Fax: (450) 437-8053
>
>
>
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> -----Message d'origine-----
> De : Cress, Andrew R [mailto:[EMAIL PROTECTED]
> Envoyé : Thursday 24 July 2008 5:20 PM
> À : Filion, Stéphane; [email protected]
> Objet : RE: [Ipmitool-devel] Ipimitool and GCC 4.3.1
>
>
> Does #pragma pack(1)/#pragma pack() work for this case with
> gcc 4.3.1?
>
>
>
> ______________________________________________________________
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On
> Behalf Of Filion, Stéphane
> Sent: Thursday, July 24, 2008 2:05 PM
> To: [email protected]
> Subject: [Ipmitool-devel] Ipimitool and GCC 4.3.1
>
>
>
> I would like to know if somebody already tried to build
> ipmitool with the GCC >= 4.1?
>
> After some investigation, I probably found a bug with GCC >=
> 4.1 This bug has an impact on the ipmitool. The bug seems to
> be related to all packed structure in the ipmitool. The
> compiler seems not to pack the structure.
>
>
> With the following example:
>
>
> ///////////////////////////////////////////////////////////////////////////////
> #include <stdio.h>
>
> struct __attribute__ ((packed)) packstruct {
> unsigned char t0 :5 ;
> unsigned char t1 :5 ;
> unsigned char t2 :5 ;
> unsigned char t3 :5 ;
> unsigned char t4 :4 ;
> };
>
> int
> main(int argc, char ** argv)
> {
> printf("size: %i\n",sizeof(struct packstruct));
>
> if(sizeof(struct packstruct) != 3)
> return(1);
> else
> return(0);
> }
>
> //////////////////////////////////////////////////////////////////////////////
>
> With this structure, the size of my structure is supposed to
> be 3 bytes, but with a GCC >= 4.1, the size of my structure is
> 5 bytes.
>
>
>
> GCC 4.1.2: Size = 5
> GCC 4.3.1: Size = 5
> GCC 4.0.2: Size = 3
> GCC 3.3.6: Size = 3
>
>
> In other hand, if I use unsigned int instead of unsigned char,
> the size of the structure is correct.
>
>
> I don't know if I'm wrong or if the IPMITool project will need
> to take an action?
>
> Best regards,
>
> Stephane Filion
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--
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Computer Scientist
High Performance Systems Division
Lawrence Livermore National Laboratory
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