LocalBits.md

C-Compatible Bit Ordering

This type alias attempts to match the bitfield ordering used by GCC on your target. The C standard permits ordering of single-bit bitfields in a structure to be implementation-defined, and GCC has been observed to use Lsb0-ordering on little-endian processors and Msb0-ordering on big-endian processors.

This has two important caveats:

• ordering of bits in an element is completely independent of the ordering of constituent bytes in memory. These have nothing to do with each other in any way. See the user guide for more information on memory representation.
• GCC wide bitfields on big-endian targets behave as <T, Lsb0> bit-slices using the _be variants of BitField accessors. They do not match Msb0 bit-wise ordering.

This type is provided solely as a convenience for narrow use cases that may match GCC’s std::bitset<N>. It makes no guarantee about what C compilers for your target actually do, and you will need to do your own investigation if you are exchanging a single buffer across FFI in this manner.