> C standard allows padding and reorder of struct entries
Almost. The ISO C standard does allow structs padding, but *not* reordering:
http://www.open-std.org/JTC1/SC22/wg14/www/docs/n1124.pdf
ISO/IEC 9899:1999 C Standard ยง6.7.2.1.13
"Within a structure object, the non-bit-field members and the units in
which bit-fields reside have addresses that increase in the order in
which they are declared. A pointer to a structure object, suitably
converted, points to its initial member (or if that member is a
bit-field, then to the unit in which it resides), and vice versa. There
may be unnamed padding within a structure object, but not at its beginning."
Dan
Lutz Donnerhacke wrote:
* Michael D. Adams wrote:
But as far as I can tell, hsc2hs doesn't support bit
fields. On top of that I'm not sure I can make any safe assumptions
about what order the bit fields are packed (LSB or MSB first).
C standard allows padding and reorder of struct entries in order to match
alignment requirements. The only exeption are bitfields, which must not
reordered and padded. This way bit fields are the only portable way to
define the binary representation in C. Unfortunly the C standard does not
specify any bit order for bit fields, but almost all implementations use
the machine specific bit order, in order to ease access to multiple bits
wide bit field and fill LSB to MSB. But there is no guarantee.
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