On Mon, 22 Feb 2016, Wink Saville wrote: > I understand "long" bit fields are in ISO, but its a gcc extension so > it would seem it should play nice with as much of the language as > possible. > > It seems the root of the problem here is the length encoding > in the type, why does gcc do that, does the standard > require it?
See the previously identified analysis of the textual history, the various C90 and C99 DRs involved, and how (as noted in 1993 in DR#120, and as is still the case) there is *no definition whatever* in ISO C of what value would be stored in a bit-field by an assignment of a value out of range of an integer type with the given number of bits, other than through the rules for conversions, which only apply if you consider the bit-field to have the restricted-width type. (And, if you wish, you could do the archaeology around the many bugs that were fixed in GCC by giving bit-fields types reflecting the values they could actually represent.) The root of the "problem" is using the extension of bit-fields wider than int, a feature that simply doesn't fit well into the C language and has unintuitive consequences. -- Joseph S. Myers jos...@codesourcery.com
