05.05.2014 15:57, Werner Benger пишет:
Privet, Andrey!
I'm wondering on this occasion, if using structs in an C API is an
issue, how do system libraries do it, for instance int fstat(int fd,
struct stat *buf); where "struct stat" is a header-defined C struct as
well. The same mechanism should be applicable to HDF5 as well, if there
are problems?
As far as I know, there is no universal solution. For example, some time
ago I tried to use UContext interface as described in
http://pubs.opengroup.org/onlinepubs/007908799/xsh/ucontext.h.html from
FreePascal. It turned out that actual binary C structs are very
different in Linux and FreeBSD (and I think they are different on
different Linuxes), let alone compiler alignment issues. I had to give up.
On Windows, all WinAPI public structs are declared as "packed", i.e.
they do not have alignment.
Here are my considerations from user perspective:
1) C struct layout is a part of binary interface.
2) Binary interface should be clearly and completely defined by
specification.
3) Currently C record layout is not completely defined. Thus, binary
specification cannot be considered complete.
4) From all possibilities, non-aligned records are most easy to use.
Best wishes,
Andrey Paramonov
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