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Re: structure packing

From: Ian Lance Taylor <iant at google dot com>
To: Mohamed Shafi <shafitvm at gmail dot com>
Cc: gcc-help at gcc dot gnu dot org, Rohit Arul Raj <rohitarulraj at gmail dot com>
Date: Fri, 22 May 2009 06:24:10 -0700
Subject: Re: structure packing
References: <ba0bd44d0905210723n5e6e85f5rea8b2b52c381d5d9@mail.gmail.com> <ba0bd44d0905210738x38bd4022s9a7b86cbce1ecadd@mail.gmail.com> <m3tz3dsl2u.fsf@google.com> <ba0bd44d0905212356j7064835dw4b215ef27d15b30d@mail.gmail.com>

Mohamed Shafi <shafitvm@gmail.com> writes:

>     I thought so. With STRICT_ALIGNMENT = 1 the compiler makes sure
> that all access are aligned. So irrespective of whether the structure
> is aligned or not to be safe it generates byte access. Am i right?
> If so in the given example the base address is 0 and the offset will
> be known to the compiler. If the compiler is aware of these two
> information can't it decide whether the structure is aligned or not?

I'm not sure.  If the compiler knows the alignment of the specific
object, it may take that into account to override the packed attribute.
However, I would not be surprised if a specific case like casting 0 to
an address does not record the alignment even though it is known, since
that is such an odd case.

Ian

References:
- structure packing
  - From: Mohamed Shafi
- Re: structure packing
  - From: Ian Lance Taylor
- Re: structure packing
  - From: Mohamed Shafi

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