http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49595
--- Comment #11 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2011-06-30 22:27:57 UTC --- On Thu, 30 Jun 2011, sandals at crustytoothpaste dot net wrote: > Your only out here is if you claim that the type in question (however named, > unnamed, or specified) is not an implementation-defined signed integer type, > and in that case, you'll need to specify that in the documentation and specify > what it *is*. You should probably document that it is a) not > implementation-defined, b) not signed (or unsigned, as appropriate), c) not > integral, or d) not a type. The implementation-defined extended integer types are documented alongside the other implementation-defined behavior in implement-c.texi: "GCC does not support any extended integer types.". Note that "char" is a standard integer type that is not a signed or unsigned integer type although it behaves like one or the other; you could think of it as a "sui generis integer type". And the right way to think of __int128 is as a "sui generis extended type", that is not an integer type although it shares some properties with them. Maybe the __fpreg type supported on IA64 is more obviously a "sui generis extended type" given the restrictions on how it can be used - but the same category contains both those types (and ARM __fp16, for another example).
