udev compile problem: udevd

udev compile problem: udevd

[Thomas Strösslin]

Hi,

I failed to compile udev-050.
in udevd.h, the structure hotplug_msg{} contains:

	char envbuf[];

This does not compile on my system (SuSE 7.3, gcc 2.95.3)

It does compile if you replace "envbuf[]" with "*envbuf"

cheers,
tom


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Re: udev compile problem: udevd

[Kay Sievers]

On Mon, 2004-12-20 at 18:40 +0100, Thomas Strösslin wrote:
> Hi,
> 
> I failed to compile udev-050.
> in udevd.h, the structure hotplug_msg{} contains:
> 
> 	char envbuf[];
> 
> This does not compile on my system (SuSE 7.3, gcc 2.95.3)
> 
> It does compile if you replace "envbuf[]" with "*envbuf"

A variable sized array is not a pointer! You will get a different
sizeof(), which may cause problems.

Kay



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Re: udev compile problem: udevd

[Dave Dodge]

On Mon, Dec 20, 2004 at 09:17:39PM +0100, Kay Sievers wrote:
> A variable sized array is not a pointer! You will get a different
> sizeof(), which may cause problems.

Beware that gcc does not conform to C99 in regards to the size of a
structure containing a flexible array.  For example:

  struct foo{ int i; char c; char arr[]; };

gcc-3.4.2/i386 reports sizeof(struct foo) as 8 and offsetof(struct foo,arr)
as 5; but C99 requires those values to be the same.  More here:

  http://gcc.gnu.org/gcc-3.4/c99status.html
  http://gcc.gnu.org/ml/gcc/2002-05/msg02844.html

                                                  -Dave Dodge


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Re: udev compile problem: udevd

[Kay Sievers]

On Mon, 2004-12-20 at 18:29 -0500, Dave Dodge wrote:
> On Mon, Dec 20, 2004 at 09:17:39PM +0100, Kay Sievers wrote:
> > A variable sized array is not a pointer! You will get a different
> > sizeof(), which may cause problems.
> 
> Beware that gcc does not conform to C99 in regards to the size of a
> structure containing a flexible array.  For example:
> 
>   struct foo{ int i; char c; char arr[]; };
> 
> gcc-3.4.2/i386 reports sizeof(struct foo) as 8 and offsetof(struct foo,arr)
> as 5; but C99 requires those values to be the same.  More here:
> 
>   http://gcc.gnu.org/gcc-3.4/c99status.html
>   http://gcc.gnu.org/ml/gcc/2002-05/msg02844.html

Interesting. Thanks for pointing this out.

Kay



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