[PATCH] D117090: Fix `readability-non-const-parameter` for parameter referenced by an lvalue

[gehry via Phabricator via cfe-commits]

Sockke created this revision.
Sockke added reviewers: danielmarjamaki, njames93, aaron.ballman, MTC.
Herald added a subscriber: carlosgalvezp.
Sockke requested review of this revision.
Herald added a project: clang-tools-extra.
Herald added a subscriber: cfe-commits.

The checker missed a check for a case when the parameter is referenced by an lvalue and this could cause build breakages.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117090

Files:
  clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
  clang-tools-extra/test/clang-tidy/checkers/readability-non-const-parameter.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/readability-non-const-parameter.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/readability-non-const-parameter.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/readability-non-const-parameter.cpp
@@ -287,3 +287,39 @@
 }
 char foo(char *s); // 2
 // CHECK-FIXES: {{^}}char foo(const char *s); // 2{{$}}
+
+void lvalueReference(int *p) {
+  // CHECK-MESSAGES-NOT: warning:
+  int &x = *p;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:32: warning: pointer parameter 'p' can be
+void constLValueReference(int *p) {
+  // CHECK-FIXES: {{^}}void constLValueReference(const int *p) {{{$}}
+  const int &x = *p;
+}
+
+void lambdaLVRef(int *p) {
+  // CHECK-MESSAGES-NOT: warning:
+  auto foo = [&]() {
+    int &x = *p;
+  };
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:28: warning: pointer parameter 'p' can be
+void lambdaConstLVRef(int *p) {
+  // CHECK-FIXES: {{^}}void lambdaConstLVRef(const int *p) {{{$}}
+  auto foo = [&]() {
+    const int &x = *p;
+  };
+}
+
+struct Temp1 {
+  Temp1(int &i) {
+    i = 10;
+  }
+};
+void constructLVRef(int *p) {
+  // CHECK-MESSAGES-NOT: warning:
+  Temp1 t(*p);
+}
Index: clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
+++ clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
@@ -83,6 +83,20 @@
       for (const auto *Arg : CE->arguments()) {
         markCanNotBeConst(Arg->IgnoreParenCasts(), true);
       }
+      // Data passed by nonconst reference should not be made const.
+      unsigned ArgNr = 0U;
+      if (const auto *CD = CE->getConstructor()) {
+        for (const auto *Par : CD->parameters()) {
+          if (ArgNr >= CE->getNumArgs())
+            break;
+          const Expr *Arg = CE->getArg(ArgNr++);
+          // Is this a non constant reference parameter?
+          const Type *ParType = Par->getType().getTypePtr();
+          if (!ParType->isReferenceType() || Par->getType().isConstQualified())
+            continue;
+          markCanNotBeConst(Arg->IgnoreParenCasts(), false);
+        }
+      }
     } else if (const auto *R = dyn_cast<ReturnStmt>(S)) {
       markCanNotBeConst(R->getRetValue(), true);
     } else if (const auto *U = dyn_cast<UnaryOperator>(S)) {
@@ -93,6 +107,9 @@
     if ((T->isPointerType() && !T->getPointeeType().isConstQualified()) ||
         T->isArrayType())
       markCanNotBeConst(VD->getInit(), true);
+    else if (T->isLValueReferenceType() &&
+             !T->getPointeeType().isConstQualified())
+      markCanNotBeConst(VD->getInit(), false);
   }
 }
 


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