[clang] [Frontend][Sema] Add CC1-only -fms-anonymous-structs to enable Microsoft anonymous struct/union feature (PR #176551)

[Riyaz Ahmad via cfe-commits]

================
@@ -0,0 +1,99 @@
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN: -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-anonymous-structs
+// RUN: %clang_cc1 -triple powerpc-ibm-aix %s -fsyntax-only -Wno-unused-value \
+// RUN: -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-anonymous-structs
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN: -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-extensions
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN: -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-compatibility
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN: -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous-dis
+
+typedef struct notnested {
+  long bad1;
+  long bad2;
+} NOTNESTED;
+
+
+typedef struct nested1 {
+  long a;
+  struct notnested var1;
+  NOTNESTED var2;
+} NESTED1;
+
+struct nested2 {
+  long b;
+  NESTED1;  // ms-anonymous-warning {{anonymous structs are a Microsoft extension}}
+            // ms-anonymous-dis-warning at -1 {{declaration does not declare anything}}
+};
+
+struct nested2 PR20573 = { .a = 3 };  // ms-anonymous-dis-error {{field designator 'a' does not refer to any field in type 'struct nested2'}}
+
+struct nested3 {
+  long d;
+  struct nested4 { // ms-anonymous-warning {{anonymous structs are a Microsoft extension}}
+                   // ms-anonymous-dis-warning at -1 {{declaration does not declare anything}}
+    long e;
+  };
+  union nested5 { // ms-anonymous-warning {{anonymous unions are a Microsoft extension}}
+                  // ms-anonymous-dis-warning at -1 {{declaration does not declare anything}}
+    long f;
+  };
+};
+
+typedef union nested6 {
+  long f;
+} NESTED6;
+
+struct test {
+  int c;
+  struct nested2;   // ms-anonymous-warning {{anonymous structs are a Microsoft extension}}
+                    // ms-anonymous-dis-warning at -1 {{declaration does not declare anything}}
+  NESTED6;   // ms-anonymous-warning {{anonymous unions are a Microsoft extension}}
+            // ms-anonymous-dis-warning at -1 {{declaration does not declare anything}}
+};
+
+void foo(void)
+{
+  struct test var;
+  var.a;      // ms-anonymous-dis-error {{no member named 'a' in 'struct test'}}
+  var.b;      // ms-anonymous-dis-error {{no member named 'b' in 'struct test'}}
+  var.c;
+  var.bad1;   // ms-anonymous-error {{no member named 'bad1' in 'struct test'}}
+              // ms-anonymous-dis-error at -1 {{no member named 'bad1' in 'struct test'}}
+  var.bad2;   // ms-anonymous-error {{no member named 'bad2' in 'struct test'}}
+              // ms-anonymous-dis-error at -1 {{no member named 'bad2' in 'struct test'}}
+}
+
+// Enumeration types with a fixed underlying type.
+const int seventeen = 17;
+typedef int Int;
+
+void pointer_to_integral_type_conv(char* ptr) {
+  char ch = (char)ptr;
+  short sh = (short)ptr;
+  ch = (char)ptr;
+  sh = (short)ptr;
+
+  // This is valid ISO C.
+  _Bool b = (_Bool)ptr;
+}
----------------
riyaz86a wrote:

Removed this block.

https://github.com/llvm/llvm-project/pull/176551