[clang-tools-extra] [clang-tidy] Add new check 'misc-static-initialization-cycle' (PR #175342)

[Baranov Victor via cfe-commits]

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Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/175342 at github.com>


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+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "StaticInitializationCycleCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DynamicRecursiveASTVisitor.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Analysis/CallGraph.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SCCIterator.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+
+// Compute (for the purpose of this check) if the value of a DeclRefExpr is used
+// (at runtime).
+// The value is not used if it appears at LHS of an assignment or it appears
+// inside a compile-time constant expression (like 'sizeof').
+static bool isUnusedValue(const DeclRefExpr *DRE, ASTContext &ACtx) {
+  ParentMapContext &PMC = ACtx.getParentMapContext();
+  DynTypedNodeList Parents = PMC.getParents(*DRE);
+  const BinaryOperator *ParentBO = nullptr;
+  while (!Parents.empty()) {
+    if (const Expr *E = Parents[0].get<Expr>()) {
+      if (E->isIntegerConstantExpr(ACtx))
+        return true;
+      if ((ParentBO = dyn_cast<BinaryOperator>(E)))
+        break;
+    }
+    Parents = PMC.getParents(Parents[0]);
+  }
----------------
vbvictor wrote:

Could we stop traversing up when some condition is met, e.g. when we hit `CompountStmt`. Walking up to `TranslationUnitDecl` for each `DeclRefExpr` seems like a very expensive operation.

https://github.com/llvm/llvm-project/pull/175342