[clang] [StaticAnalyzer] Make it a noop when initializing a field of empty record (PR #138594)

[via cfe-commits]

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@@ -0,0 +1,45 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus -verify %s -DEMPTY_CLASS
+
+// expected-no-diagnostics
+
+// This test reproduces the issue that previously the static analyzer
+// initialized an [[__no_unique_address__]] empty field to zero,
+// over-writing a non-empty field with the same offset.
+
+namespace std {
+#ifdef EMPTY_CLASS
+
+  template <typename T>
+  class default_delete {
+    T dump();
+    static T x;
+  };
+  template <class _Tp, class _Dp = default_delete<_Tp> >
+#else
+
+  struct default_delete {};
+  template <class _Tp, class _Dp = default_delete >
+#endif
+  class unique_ptr {
+    [[__no_unique_address__]]  _Tp * __ptr_;
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isuckatcs wrote:

Hmm, we get a failing test that says, this attribute doesn't exist on Windows. We need `msvc::no_uniqu_address` there, according to the [documentation](https://clang.llvm.org/docs/AttributeReference.html#no-unique-address).

https://github.com/llvm/llvm-project/pull/138594