[PATCH] D55791: [libcxx] Simplify conditional definition of _LIBCPP_HAS_NO_ALIGNED_ALLOCATION

Mon Jan 7 10:50:40 PST 2019

mclow.lists added a comment.

In D55791#1348497 <https://reviews.llvm.org/D55791#1348497>, @ldionne wrote:

> In D55791#1348291 <https://reviews.llvm.org/D55791#1348291>, @mclow.lists wrote:
>
> > In general, we *do* protect against user-defined defines.  
> >  This, and defining stuff as negative (`_LIBCPP_HAS_NO_XXX`) lets users disable parts of the libc++ functionality by defining the macros.
> >
> > So I think we should leave this "as is"
>
>
> The problem I have with this is that we're hence implicitly supporting this use case, which means we should make sure we don't break it, we should add a tester with this configuration, and we should document that this macro can be used to alter the behaviour of the library. Either we should do this if we have a reason to, or we should remove this accidental API by not checking whether the user defines the macro. Does this make sense?

90 seconds of grepping found the following extant macros in `<__config>`: _LIBCPP_HAS_NO_ALIGNED_ALLOCATION, _LIBCPP_HAS_NO_ASAN, _LIBCPP_HAS_NO_ATOMIC_HEADER, _LIBCPP_HAS_NO_AUTO_TYPE, _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF, _LIBCPP_HAS_NO_BUILTIN_OPERATOR_NEW_DELETE, _LIBCPP_HAS_NO_CONSTEXPR, _LIBCPP_HAS_NO_COROUTINES, _LIBCPP_HAS_NO_CXX14_CONSTEXPR, _LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS, _LIBCPP_HAS_NO_DECLTYPE, _LIBCPP_HAS_NO_DEDUCTION_GUIDES, _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS, _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE, _LIBCPP_HAS_NO_INT128, _LIBCPP_HAS_NO_IS_AGGREGATE, _LIBCPP_HAS_NO_LAMBDAS, _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION, _LIBCPP_HAS_NO_LONG_LONG, _LIBCPP_HAS_NO_MONOTONIC_CLOCK, _LIBCPP_HAS_NO_NOEXCEPT, _LIBCPP_HAS_NO_NULLPTR, _LIBCPP_HAS_NO_OFF_T_FUNCTIONS, _LIBCPP_HAS_NO_PRAGMA_PUSH_POP_MACRO, _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER, _LIBCPP_HAS_NO_RVALUE_REFERENCES, _LIBCPP_HAS_NO_SPACESHIP_OPERATOR, _LIBCPP_HAS_NO_STDIN, _LIBCPP_HAS_NO_STDOUT, _LIBCPP_HAS_NO_STRONG_ENUMS, _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS, _LIBCPP_HAS_NO_THREADS, _LIBCPP_HAS_NO_UNICODE_CHARS, _LIBCPP_HAS_NO_VARIABLE_TEMPLATES, _LIBCPP_HAS_NO_VARIADICS, _LIBCPP_HAS_NO_VECTOR_EXTENSION.

As far as I know, we don't have testers for all of these.

Repository:
  rCXX libc++

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55791/new/

https://reviews.llvm.org/D55791