[clang] [analyzer] Match dangling subobjects by their base region in DanglingPtrDeref (PR #211552)

[Balázs Benics via cfe-commits]

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@@ -112,3 +112,56 @@ void inlined_callee_single_report() {
   // expected-note at -1 {{Calling 'deref_param'}}
   (void)r;
 }
+
+struct MyBuffer {
+  char buffer[8];
+};
+
+void member_subregion_dangling_deref() {
+  const char *p = nullptr;
+  {
+    struct MyBuffer tmp_buffer = {};
+    p = tmp_buffer.buffer;
+  }
+  // expected-note at -1 {{'tmp_buffer.buffer[0]' is destroyed here}}
+  char c = *p;
+  // expected-warning at -1 {{Use of 'tmp_buffer.buffer[0]' after its lifetime ended}}
+  // expected-note at -2    {{Use of 'tmp_buffer.buffer[0]' after its lifetime ended}}
+  (void)c;
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steakhal wrote:

An alternative way of phrasing this is `return *p;`
I don't mind this either - I just wanted to share this technique.

https://github.com/llvm/llvm-project/pull/211552