diff options
| -rw-r--r-- | clang/include/clang/Basic/TargetCXXABI.h | 21 |
1 files changed, 6 insertions, 15 deletions
diff --git a/clang/include/clang/Basic/TargetCXXABI.h b/clang/include/clang/Basic/TargetCXXABI.h index b1be4027251..60343fe99c1 100644 --- a/clang/include/clang/Basic/TargetCXXABI.h +++ b/clang/include/clang/Basic/TargetCXXABI.h @@ -277,27 +277,18 @@ public: /// padding of a base class? /// /// This decision cannot be changed without breaking platform ABI - /// compatibility, and yet it is tied to language guarantees which - /// the committee has so far seen fit to strengthen no less than - /// three separate times: - /// - originally, there were no restrictions at all; - /// - C++98 declared that objects could not be allocated in the - /// tail padding of a POD type; - /// - C++03 extended the definition of POD to include classes - /// containing member pointers; and - /// - C++11 greatly broadened the definition of POD to include - /// all trivial standard-layout classes. - /// Each of these changes technically took several existing - /// platforms and made them permanently non-conformant. + /// compatibility. In ISO C++98, tail padding reuse was only permitted for + /// non-POD base classes, but that restriction was removed retroactively by + /// DR 43, and tail padding reuse is always permitted in all de facto C++ + /// language modes. However, many platforms use a variant of the old C++98 + /// rule for compatibility. enum TailPaddingUseRules { /// The tail-padding of a base class is always theoretically - /// available, even if it's POD. This is not strictly conforming - /// in any language mode. + /// available, even if it's POD. AlwaysUseTailPadding, /// Only allocate objects in the tail padding of a base class if /// the base class is not POD according to the rules of C++ TR1. - /// This is non-strictly conforming in C++11 mode. UseTailPaddingUnlessPOD03, /// Only allocate objects in the tail padding of a base class if |
