Re: directly serializing structs

 James Kanze <>
Sun, 24 Jun 2007 12:27:31 -0000
On Jun 23, 11:58 am, "JohnQ" <>

"Cagdas Ozgenc" <> wrote in message

When directly serializing C++ structures to a file with the standard
library functions giving the address of the data and length of
structure using the sizeof operator, do I risk portability because of
different compilers packing structures into different sizes or
components of this structure to different address boundaries (for
example placing in multiples of 4 on a 32bit system)? Once the file is
serialized, does the same code compiled by another compiler or even
the same compiler but a different version carry the risk of not
reading the contents properly?

Does your software/application require that much portability? Why struggle
with "write once, compile anywhere" if you're only targeting one platform=


even only one machine, for instances?

And one version of one compiler with one set of compiler options.

I guess he's a professional.


I can think of 3 issues that prevent the the "blast struct all
over" concept from working: endianess, padding/alignment,
datatype sizes.

Representation in general. For floating point, it's a real
problem, even today. For integers, there is also at least one
machine on the market which uses 36 bit ones complement
integers, but it's not very wide spread, and many people can
afford to ignore it.

Just be aware of the restriction, and document it, so that some
maintenance programmer in the future doesn't get bitten. And
whatever you do, document all external formats, so a maintenance
programmer has a chance of implementing them on some future

The first one is the party spoiler.

I'd say that the different representations are even worse.
(Note too that "endianness" isn't a good word, since it suggests
two possible arrangements. At least three are widespread.)

James Kanze (Gabi Software) email:
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