--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/Sema/reserved-identifier.c	Tue Jun 08 06:07:14 2021 +0900
@@ -0,0 +1,65 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wreserved-identifier -Wno-visibility %s
+
+#define __oof foo__ // expected-warning {{macro name is a reserved identifier}}
+
+int foo__bar() { return 0; }    // no-warning
+static int _bar() { return 0; } // expected-warning {{identifier '_bar' is reserved because it starts with '_' at global scope}}
+static int _Bar() { return 0; } // expected-warning {{identifier '_Bar' is reserved because it starts with '_' followed by a capital letter}}
+int _foo() { return 0; }        // expected-warning {{identifier '_foo' is reserved because it starts with '_' at global scope}}
+
+// This one is explicitly skipped by -Wreserved-identifier
+void *_; // no-warning
+
+void foo(unsigned int _Reserved) { // expected-warning {{identifier '_Reserved' is reserved because it starts with '_' followed by a capital letter}}
+  unsigned int __1 =               // expected-warning {{identifier '__1' is reserved because it starts with '__'}}
+      _Reserved;                   // no-warning
+  goto __reserved;                 // expected-warning {{identifier '__reserved' is reserved because it starts with '__'}}
+__reserved: // expected-warning {{identifier '__reserved' is reserved because it starts with '__'}}
+            ;
+}
+
+void foot(unsigned int _not_reserved) {} // no-warning
+
+enum __menu { // expected-warning {{identifier '__menu' is reserved because it starts with '__'}}
+  __some,     // expected-warning {{identifier '__some' is reserved because it starts with '__'}}
+  _Other,     // expected-warning {{identifier '_Other' is reserved because it starts with '_' followed by a capital letter}}
+  _other      // expected-warning {{identifier '_other' is reserved because it starts with '_' at global scope}}
+};
+
+struct __babar { // expected-warning {{identifier '__babar' is reserved because it starts with '__'}}
+};
+
+struct _Zebulon;   // expected-warning {{identifier '_Zebulon' is reserved because it starts with '_' followed by a capital letter}}
+struct _Zebulon2 { // expected-warning {{identifier '_Zebulon2' is reserved because it starts with '_' followed by a capital letter}}
+} * p;
+struct _Zebulon3 *pp; // expected-warning {{identifier '_Zebulon3' is reserved because it starts with '_' followed by a capital letter}}
+
+typedef struct {
+  int _Field; // expected-warning {{identifier '_Field' is reserved because it starts with '_' followed by a capital letter}}
+  int _field; // no-warning
+} _Typedef;   // expected-warning {{identifier '_Typedef' is reserved because it starts with '_' followed by a capital letter}}
+
+int foobar() {
+  return foo__bar(); // no-warning
+}
+
+struct _reserved { // expected-warning {{identifier '_reserved' is reserved because it starts with '_' at global scope}}
+  int a;
+} cunf(void) {
+  return (struct _reserved){1};
+}
+
+// FIXME: According to clang declaration context layering, _preserved belongs to
+// the translation unit, so we emit a warning. It's unclear that's what the
+// standard mandate, but it's such a corner case we can live with it.
+void func(struct _preserved { int a; } r) {} // expected-warning {{identifier '_preserved' is reserved because it starts with '_' at global scope}}
+
+extern char *_strdup(const char *); // expected-warning {{identifier '_strdup' is reserved because it starts with '_' at global scope}}
+
+// Don't warn on redecleration
+extern char *_strdup(const char *); // no-warning
+
+void ok() {
+  void _ko();           // expected-warning {{identifier '_ko' is reserved because it starts with '_' at global scope}}
+  extern int _ko_again; // expected-warning {{identifier '_ko_again' is reserved because it starts with '_' at global scope}}
+}