[clang] [C2y] Allow static local variables in inline functions with external … (PR #167086)

[Pranjal Prajapati via cfe-commits]

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+// RUN: %clang_cc1 -verify=good -pedantic -Wall -std=c2y %s
+// RUN: %clang_cc1 -verify=compat,expected -pedantic -Wall -Wpre-c2y-compat -std=c2y %s
+// RUN: %clang_cc1 -verify=ped,expected -pedantic -Wall -std=c23 %s
+// RUN: %clang_cc1 -verify=ped,expected -pedantic -Wall -std=c17 %s
+// good-no-diagnostics
+
+/* WG14 N3622: Clang 22
+ * Allow static local variables in extern inline functions
+ *
+ * This verifies that a constraint from previous standards is no longer
+ * triggered in C2y mode. The constraint is regarding static local
+ * variables in inline functions with external linkage.
+ */
+
+inline void func1(void) {   // expected-note {{use 'static' to give inline function 'func1' internal linkage}}
+    static int x = 0;   /* ped-warning {{non-constant static local variable in an inline function with external linkage is a C2y extension}}
+                      compat-warning {{non-constant static local variable in an inline function with external linkage is incompatible with standards before C2y}}
+                    */
+    (void)x;
+}
+
+inline void func2(void) {
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Pranjal095 wrote:

The first test is to ensure that the new C2y feature works with the specified diagnostics. The second test is to ensure that no false positives have popped up during the process.

https://github.com/llvm/llvm-project/pull/167086