[clang] [analyzer] Ignoring `T v=v; ` idiom for uninitialized variable checker and dead store checker (PR #187530)

[Ella Ma via cfe-commits]

================
@@ -620,6 +620,21 @@ void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred,
     return;
   }
 
+  // Self-assignment initialization in variable declaration,
+  // i.e., `int x = x;`,
+  // is a C idiom to suppress warnings of unused variables.
+  // This filter will not match variables of C++ record types, but will match
+  // C++ references. Allow references continuing here to make the undefined
+  // value checker report self-assignments of C++ references.
+  if (const Expr *EI = VD->getInit()) {
+    if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(EI->IgnoreImpCasts()))
----------------
Snape3058 wrote:

OK. But what in my mind is:

```
#define DEFINE_VAR(TYPE, NAME) TYPE NAME = NAME
DEFINE_VAR(int, x);
```

Anyway, I will add the parentheses in the next version.

https://github.com/llvm/llvm-project/pull/187530