[libcxx-commits] [libcxxabi] [libcxx] [libc++] Remove dependence on <ciso646> (PR #73271)

[Michael Kenzel via libcxx-commits]

================
@@ -12,15 +12,15 @@
 
 // Attempt to get STL specific macros like _LIBCPP_VERSION using the most
 // minimal header possible. If we're testing libc++, we should use `<__config>`.
-// If <__config> isn't available, fall back to <ciso646>.
+// If <__config> isn't available, fall back to <version>.
 #ifdef __has_include
 # if __has_include("<__config>")
 #   include <__config>
 #   define TEST_IMP_INCLUDED_HEADER
 # endif
 #endif
 #ifndef TEST_IMP_INCLUDED_HEADER
-#include <ciso646>
+#  include <version>
----------------
michael-kenzel wrote:

I have now replaced this whole part
```cpp
// Attempt to get STL specific macros like _LIBCPP_VERSION using the most
// minimal header possible. If we're testing libc++, we should use `<__config>`.
// If <__config> isn't available, fall back to <ciso646>.
#ifdef __has_include
# if __has_include("<__config>")
#   include <__config>
#   define TEST_IMP_INCLUDED_HEADER
# endif
#endif
#ifndef TEST_IMP_INCLUDED_HEADER
#include <ciso646>
#endif
```
with just
```cpp
#ifdef __has_include
# if __has_include("<version>")
#   include <version>
# else
#   include <ciso646>
# endif
#else
#  include <ciso646>
#endif
```
It doesn't seem necessary to explicitly check and include `__config.h` since `<version.h>` already does that for libc++, so this seemed like a valid simplification?

https://github.com/llvm/llvm-project/pull/73271