Am 04.03.2013 17:10, schrieb Luca Olivetti:
Al 03/03/13 21:52, En/na Sven Barth ha escrit:
On 03.03.2013 20:32, Luca Olivetti wrote:
Al 03/03/13 14:34, En/na Sven Barth ha escrit:
For "packed" there is the
guarantee though that the layout will stay the same.
Are you sure? Does the same guarantee apply to bitpacked?
Lately I've become lazy, and instead of manually decoding data (bits,
bytes, words) read from a device, I'm relying on packed/bitpacked
records, but I wasn't sure that upgrading the compiler wouldn't break my
code.
For "packed" it is guaranteed (*), because this is the whole purpose of
this modifier, for "bitpacked" it is not. It just tells the compiler to
pack the record as densly as possible, but depending on the platform
this might not be possible.
At the moment I don't care about the platform, only about different
(newer) versions of the compiler.
Currently , with 2.6.0, bitpacked under win32 gives me the correct
layout (I have to adjust endianness for words/dwords but individual bit
fields are where they should be).
Can I be sure that 2.6.2 (and later version) won't break my code?
I can only give you a guarantee for packed. For bitpacked it's
documented that you shouldn't rely on the binary format.
Regards,
Sven
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