[PATCH] D142609: [Clang] Fix -Wconstant-logical-operand when LHS is a constant

[Shivam Gupta via Phabricator via cfe-commits]

xgupta created this revision.
xgupta added reviewers: nickdesaulniers, aaron.ballman.
Herald added a project: All.
xgupta requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

This fix PR37919

The below code produces -Wconstant-logical-operand for the first statement,
but not the second.

void foo(int x) {
if (x && 5) {}
if (5 && x) {}
}


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142609

Files:
  clang/lib/Sema/SemaExpr.cpp


Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -13593,18 +13593,21 @@
     Diag(Loc, diag::warn_enum_constant_in_bool_context);
 
   // Diagnose cases where the user write a logical and/or but probably meant a
-  // bitwise one.  We do this when the LHS is a non-bool integer and the RHS
-  // is a constant.
-  if (!EnumConstantInBoolContext && LHS.get()->getType()->isIntegerType() &&
-      !LHS.get()->getType()->isBooleanType() &&
-      RHS.get()->getType()->isIntegerType() && !RHS.get()->isValueDependent() &&
+  // bitwise one.  We do this when one of the operand is a non-bool integer and
+  // the other is a constant.
+  if (!EnumConstantInBoolContext &&
+      ((RHS.get()->getType()->isIntegerType() && !RHS.get()->getType()->isBooleanType() &&
+      LHS.get()->getType()->isIntegerType() && !LHS.get()->isValueDependent()) ||
+      ( RHS.get()->getType()->isIntegerType() && !RHS.get()->getType()->isBooleanType() &&
+      LHS.get()->getType()->isIntegerType() && !LHS.get()->isValueDependent())) &&
       // Don't warn in macros or template instantiations.
       !Loc.isMacroID() && !inTemplateInstantiation()) {
-    // If the RHS can be constant folded, and if it constant folds to something
+    // If the operand can be constant folded, and if it constant folds to something
     // that isn't 0 or 1 (which indicate a potential logical operation that
     // happened to fold to true/false) then warn.
-    // Parens on the RHS are ignored.
+    // Parens on the operand are ignored.
     Expr::EvalResult EVResult;
+
     if (RHS.get()->EvaluateAsInt(EVResult, Context)) {
       llvm::APSInt Result = EVResult.Val.getInt();
       if ((getLangOpts().Bool && !RHS.get()->getType()->isBooleanType() &&
@@ -13626,6 +13629,28 @@
                                  RHS.get()->getEndLoc()));
       }
     }
+
+    if (LHS.get()->EvaluateAsInt(EVResult, Context)) {
+      llvm::APSInt Result = EVResult.Val.getInt();
+      if ((getLangOpts().Bool && !LHS.get()->getType()->isBooleanType() &&
+           !LHS.get()->getExprLoc().isMacroID()) ||
+          (Result != 0 && Result != 1)) {
+        Diag(Loc, diag::warn_logical_instead_of_bitwise)
+            << LHS.get()->getSourceRange() << (Opc == BO_LAnd ? "&&" : "||");
+        // Suggest replacing the logical operator with the bitwise version
+        Diag(Loc, diag::note_logical_instead_of_bitwise_change_operator)
+            << (Opc == BO_LAnd ? "&" : "|")
+            << FixItHint::CreateReplacement(
+                   SourceRange(Loc, getLocForEndOfToken(Loc)),
+                   Opc == BO_LAnd ? "&" : "|");
+        if (Opc == BO_LAnd)
+          // Suggest replacing "kNonZero && foo() " with "Foo()"
+          Diag(Loc, diag::note_logical_instead_of_bitwise_remove_constant)
+              << FixItHint::CreateRemoval(
+                     SourceRange(getLocForEndOfToken(RHS.get()->getEndLoc()),
+                                 LHS.get()->getEndLoc()));
+      }
+    }
   }
 
   if (!Context.getLangOpts().CPlusPlus) {


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