Re: [PATCH 0/7] ensure index is set for all OBJ_COMMIT objects variable

> Here's a series to address the bug I mentioned earlier by catching the
> conversion of OBJ_NONE to OBJ_COMMIT in a central location and setting
> the index there.
> 
> I've included your patch 1/2 unchanged in the beginning, as I build on
> top of it (and your patch 2/2 is no longer applicable).  The rest is
> refactoring leading up to patch 6 to fix the bug. Patch 7 is a bonus
> cleanup.

> 
> I'd hoped to cap off the series by converting the "type" field of
> "struct commit" to a "const unsigned type : 3", which would avoid any
> new callers being added that would touch it without going through the
> proper procedure.  However, it's a bitfield, which makes it hard to cast
> the constness away in the actual setter function. My best attempt was to
> use a union with matching const and non-const members, but that would
> mean changing all of the sites which read the field (and there are many)
> to use "object->type.read".
> 
> There may be a clever solution hiding in a dark corner of C, but I
> suspect we are entering a realm of portability problems with older
> compilers (I even saw one compiler's documentation claim that "const"
> was forbidden on bitfields, even though C99 has an example which does
> it).