[DougGwyn]

I'm not sure what your requirement is. Usually things work out if you're careful not to assume any specific value for alignment etc. It may mean a few unused bytes here and there, but keeping things simple and portable often pays off.

[quelsolaar]

Being able to know your alignments is VERY important for a lot of network implementations. They are all defined by the ABIs, but its very annoying that the standard keeps thinking that alignment is unknowable, when in fact its impossible to implement a ABI without defining it. One of the reasons I stick to C89.

[DougGwyn]

Note that the ABIs cover endianness as well as value range and/or object widths. In general, one needs to have explicit marshaling and unmarshaling functions to map from network octet array and C internal data representation. Failure to get this right is (or used to be) a common bug for code developed and tested on too few architectures.

[quelsolaar]

Sure, it wont be portable between any architectures, but a lot of times you know you will be on a little endian platform where types are aligned to their sizeofs. That covers a lot of ground and the performance gains you get from optimizing with this in mind is significant. There is value in C being able to be portable, but there is also a huge value in being able to write non-portable code that takes advantage of what you know about the platform. C needs to acknowledge that that is a legitimate use case.