[PATCH] D131067: [analyzer] Treat values passed as parameter as escaped

Thomas WeiƟschuh via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Wed Aug 3 04:31:42 PDT 2022


t-8ch created this revision.
Herald added subscribers: steakhal, manas, ASDenysPetrov, martong, dkrupp, donat.nagy, Szelethus, mikhail.ramalho, a.sidorin, szepet, baloghadamsoftware, xazax.hun.
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t-8ch requested review of this revision.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131067

Files:
  clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
  clang/test/Analysis/dead-stores.cpp


Index: clang/test/Analysis/dead-stores.cpp
===================================================================
--- clang/test/Analysis/dead-stores.cpp
+++ clang/test/Analysis/dead-stores.cpp
@@ -217,3 +217,26 @@
   return i + j;
 }
 
+//===----------------------------------------------------------------------===//
+// Dead store checking involving references.
+//===----------------------------------------------------------------------===//
+
+void functionReferenceParameter(int &i) {
+  i = 5; // no warning
+}
+
+struct constructorReferenceParameter {
+  constructorReferenceParameter(int &i) {
+    i = 5; // no warning
+  }
+};
+
+void referenceParameters() {
+  int i = 5;
+  functionReferenceParameter(i);
+  i = 6;
+
+  int j = 7;
+  constructorReferenceParameter k(j);
+  j = 8;
+}
Index: clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
@@ -483,12 +483,21 @@
   void operator()(const Stmt *S) {
     // Check for '&'. Any VarDecl whose address has been taken we treat as
     // escaped.
-    // FIXME: What about references?
     if (auto *LE = dyn_cast<LambdaExpr>(S)) {
       findLambdaReferenceCaptures(LE);
       return;
     }
 
+    if (auto *CE = dyn_cast<CallExpr>(S)) {
+      findCallReferenceParameters(CE);
+      return;
+    }
+
+    if (auto *CE = dyn_cast<CXXConstructExpr>(S)) {
+      findConstructorReferenceParameters(CE);
+      return;
+    }
+
     const UnaryOperator *U = dyn_cast<UnaryOperator>(S);
     if (!U)
       return;
@@ -522,6 +531,33 @@
         Escaped.insert(VD);
     }
   }
+
+  void findReferenceParameter(const ParmVarDecl *Param, const Expr *Arg) {
+    if (Param->getType()->isReferenceType()) {
+      if (auto *DRE = dyn_cast<DeclRefExpr>(Arg)) {
+        if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
+          Escaped.insert(VD);
+        }
+      }
+    }
+  }
+
+  void findCallReferenceParameters(const CallExpr *CE) {
+    if (auto *FD = dyn_cast<FunctionDecl>(CE->getCalleeDecl())) {
+      unsigned numParams = FD->getNumParams();
+      for (unsigned i = 0; i < numParams; ++i) {
+        findReferenceParameter(FD->getParamDecl(i), CE->getArg(i));
+      }
+    }
+  }
+
+  void findConstructorReferenceParameters(const CXXConstructExpr *CE) {
+    const FunctionDecl *FD = CE->getConstructor();
+    unsigned numParams = FD->getNumParams();
+    for (unsigned i = 0; i < numParams; ++i) {
+      findReferenceParameter(FD->getParamDecl(i), CE->getArg(i));
+    }
+  }
 };
 } // end anonymous namespace
 


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