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

[Daniel Black via cfe-commits]

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@@ -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()))
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grooverdan wrote:

I've never seen the `T v = (v)` case used, from my point of view, whatever is easiest.

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