[clang] [C23] Use thread_local semantics (PR #70107)

[via cfe-commits]

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@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c23 %s -verify
+
+// Ensure that thread_local and _Thread_local are synonyms in C23 and both
+// restrict local variables to be explicitly static or extern.
+void func(void) {
+  // FIXME: it would be nice if the diagnostic said 'thread_local' in this case.
+  thread_local int i = 12;  // expected-error {{'_Thread_local' variables must have global storage}}
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cor3ntin wrote:

Another solution would be to say 'thread local variables' which is spelling agnostic.

https://github.com/llvm/llvm-project/pull/70107