[KJ] stumped... implicitly truncated warning mystery

[KJ] stumped... implicitly truncated warning mystery

[Jesse Millan]

Hey all,

GCC4.0.0 is giving me a warning that I cant seem to get rid of. In the
file drivers/net/wireless/wavelan_cs.c on lines 3607 and 3608 is the
following assignment:

cfblk.ifrm_spc = 0x20;
cfblk.slottim_low = 0x20;

where ifrm_spc and slottim_low are both of type unsigned char.

Compiling on a X86_64 emits the warning: large integer implicitly
truncated to unsigned type.

Explicitly casting 0x20 to unsigned char or u_char does not get rid of
the warning. Also, the warning starts at values 0x10 and above.

Any ideas/leads would be greatly appreciated.

-- 
Jesse Millan
CNS Unix Team
Portland State University
Phone: (503) 725-9151
Mobile: (503) 453-0748
GPG key: www.system-calls.com/gpg.php

grep --recursive --ignore-case 'SHOULD WORK' /usr/src/linux/* | wc
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Re: [KJ] stumped... implicitly truncated warning mystery

[Dave Jones]

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On Wed, Jul 06, 2005 at 10:48:46AM -0700, Jesse Millan wrote:
 > 
 > Hey all,
 > 
 > GCC4.0.0 is giving me a warning that I cant seem to get rid of. In the
 > file drivers/net/wireless/wavelan_cs.c on lines 3607 and 3608 is the
 > following assignment:
 > 
 > cfblk.ifrm_spc = 0x20;
 > cfblk.slottim_low = 0x20;
 > 
 > where ifrm_spc and slottim_low are both of type unsigned char.

No, look again.  They are bitfields.

  u_char        : 4,
     ifrm_spc   : 4;

4 bits isn't enough space to encode 0x20 which is 0b100000

  u_char        : 5,
     slottim_low : 3;

Likewise, 3 bits is too small.

		Dave


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Re: [KJ] stumped... implicitly truncated warning mystery

[Jesse Millan]

Dave Jones wrote:
> On Wed, Jul 06, 2005 at 10:48:46AM -0700, Jesse Millan wrote:
>  > 
>  > Hey all,
>  > 
>  > GCC4.0.0 is giving me a warning that I cant seem to get rid of. In the
>  > file drivers/net/wireless/wavelan_cs.c on lines 3607 and 3608 is the
>  > following assignment:
>  > 
>  > cfblk.ifrm_spc = 0x20;
>  > cfblk.slottim_low = 0x20;
>  > 
>  > where ifrm_spc and slottim_low are both of type unsigned char.
> 
> No, look again.  They are bitfields.
> 
>   u_char        : 4,
>      ifrm_spc   : 4;
> 
> 4 bits isn't enough space to encode 0x20 which is 0b100000
> 
>   u_char        : 5,
>      slottim_low : 3;
> 
> Likewise, 3 bits is too small.
> 
> 		Dave
> 
> 

Thank you Dave!

-- 
Jesse Millan
CNS Unix Team
Portland State University
Phone: (503) 725-9151
Mobile: (503) 453-0748
GPG key: www.system-calls.com/gpg.php

grep --recursive --ignore-case 'SHOULD WORK' /usr/src/linux/* | wc
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Re: [KJ] stumped... implicitly truncated warning mystery

[Alexey Dobriyan]

On Wednesday 06 July 2005 21:48, Jesse Millan wrote:
> GCC4.0.0 is giving me a warning that I cant seem to get rid of. In the
> file drivers/net/wireless/wavelan_cs.c on lines 3607 and 3608 is the
> following assignment:
> 
> cfblk.ifrm_spc = 0x20;
> cfblk.slottim_low = 0x20;
> 
> where ifrm_spc and slottim_low are both of type unsigned char.

They are bitfields.

drivers/net/wireless/i82593.h:

168	  u_char            : 4,
169	         ifrm_spc   : 4;
170	  u_char            : 5,
171	         slottim_low : 3;
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