[clang] [clang] Add __nullptr as a keyword to C (PR #123119)

[Erich Keane via cfe-commits]

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@@ -113,5 +113,3 @@ void foo(void *);
 void bar() { foo(__nullptr); }
 static_assert(nullptr == __nullptr);
 static_assert(_Generic(typeof(__nullptr), nullptr_t: true, default: false));
-_Static_assert(__nullptr == 0); // Test that its value matches that of NULL
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erichkeane wrote:

I would probably leave the tests from aaron in BOTH modes, but otherwise LGTM.

https://github.com/llvm/llvm-project/pull/123119