EricWF added a comment.
The tests LGTM. The implementation still needs some tweaks. Thanks for working
on this.
================
Comment at: include/__config:925
+#if !__has_builtin(__builtin_memcpy)
+#define _LIBCPP_HAS_NO_BUILTIN_MEMCPY
----------------
AntonBikineev wrote:
> EricWF wrote:
> > What about GCC? Surely it implements some if not most of these.
> Thanks, good point. I've done it in the same way as it is done for
> __buitin_addressof. On the other hand, gcc has an option -fno-builtin to
> disable them. That way it *won't* compile. I try to stick to the current
> solution though.
A couple of problems with your usage of `_GNUC_VER`.
First `_GNUC_VER` is always 421 when using Clang, so the above check never
fails with Clang.
Second we require at least GCC 4.8/4.9. Don't bother configuring for anything
older than that.
================
Comment at: include/__string:213
- static inline int compare(const char_type* __s1, const char_type* __s2,
size_t __n) _NOEXCEPT
- {return __n == 0 ? 0 : memcmp(__s1, __s2, __n);}
- static inline size_t length(const char_type* __s) _NOEXCEPT {return
strlen(__s);}
- static inline const char_type* find(const char_type* __s, size_t __n,
const char_type& __a) _NOEXCEPT
- {return __n == 0 ? NULL : (const char_type*) memchr(__s,
to_int_type(__a), __n);}
+#if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_CXX14_CONSTEXPR)
+ static inline constexpr int
----------------
mclow.lists wrote:
> AntonBikineev wrote:
> > EricWF wrote:
> > > wow. This is #ifdef hell. Please find a way to do it with less (or
> > > hopefully no) conditional compilation blocks.
> > yep, this is generic hell. I want to cover as many cases as possible, i.e.
> > combinations of (is_constexpr x has_builtin_xxx) for every function. I'm
> > open to suggestions
> How about (for compare, say) you just forget about `memcmp`. Either call
> `__builtin_memcmp` if it is available, or use a hand-rolled loop.
>
> Note: gcc has had `__builtin_memcmp` since at least 4.8. (and it is constexpr)
>
> And just mark the function with `_LIBCPP_CONSTEXPR_AFTER_CXX14`.
Exactly what @mclow.lists said. That seems like the correct solution. We're
*always* going to have `__builtin_memcmp` for all of our supported compilers
AFAIK.
https://reviews.llvm.org/D26896
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