r183688 - Add a new warning, -Wlogical-not-parentheses, to -Wparentheses.

Richard Trieu rtrieu at google.com
Mon Jun 10 11:52:07 PDT 2013


Author: rtrieu
Date: Mon Jun 10 13:52:07 2013
New Revision: 183688

URL: http://llvm.org/viewvc/llvm-project?rev=183688&view=rev
Log:
Add a new warning, -Wlogical-not-parentheses, to -Wparentheses.

This warning triggers on the logical not of a non-boolean expression on the
left hand side of comparison.  Often, the user meant to negate the comparison,
not just the left hand side of the comparison.  Two notes are also emitted,
the first with a fix-it to add parentheses around the comparison, and the other
to put parenthesis around the not expression to silence the warning.

bool not_equal(int x, int y) {
  return !x == y;  // warn here
}

  return !(x == y);  // first fix-it, to negate comparison.

  return (!x) == y;  // second fix-it, to silence warning.

Added:
    cfe/trunk/test/SemaCXX/warn-logical-not-compare.cpp
Modified:
    cfe/trunk/include/clang/Basic/DiagnosticGroups.td
    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
    cfe/trunk/lib/Sema/SemaExpr.cpp

Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=183688&r1=183687&r2=183688&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Mon Jun 10 13:52:07 2013
@@ -136,6 +136,7 @@ def FourByteMultiChar : DiagGroup<"four-
 def GlobalConstructors : DiagGroup<"global-constructors">;
 def BitwiseOpParentheses: DiagGroup<"bitwise-op-parentheses">;
 def LogicalOpParentheses: DiagGroup<"logical-op-parentheses">;
+def LogicalNotParentheses: DiagGroup<"logical-not-parentheses">;
 def ShiftOpParentheses: DiagGroup<"shift-op-parentheses">;
 def OverloadedShiftOpParentheses: DiagGroup<"overloaded-shift-op-parentheses">;
 def DanglingElse: DiagGroup<"dangling-else">;
@@ -368,6 +369,7 @@ def DuplicateArgDecl : DiagGroup<"duplic
 def ParenthesesOnEquality : DiagGroup<"parentheses-equality">;
 def Parentheses : DiagGroup<"parentheses",
                             [LogicalOpParentheses,
+                             LogicalNotParentheses,
                              BitwiseOpParentheses,
                              ShiftOpParentheses,
                              OverloadedShiftOpParentheses,

Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=183688&r1=183687&r2=183688&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Jun 10 13:52:07 2013
@@ -4435,6 +4435,14 @@ def warn_null_in_comparison_operation :
   "%select{(%1 and NULL)|(NULL and %1)}0">,
   InGroup<NullArithmetic>;
 
+def warn_logical_not_on_lhs_of_comparison : Warning<
+  "logical not is only applied to the left hand side of this comparison">,
+  InGroup<LogicalNotParentheses>;
+def note_logical_not_fix : Note<
+  "add parentheses after the '!' to evaluate the comparison first">;
+def note_logical_not_silence_with_parens : Note<
+  "add parentheses around left hand side expression to silence this warning">;
+
 def err_invalid_this_use : Error<
   "invalid use of 'this' outside of a non-static member function">;
 def err_this_static_member_func : Error<

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=183688&r1=183687&r2=183688&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Mon Jun 10 13:52:07 2013
@@ -7250,6 +7250,45 @@ static void diagnoseObjCLiteralCompariso
   }
 }
 
+static void diagnoseLogicalNotOnLHSofComparison(Sema &S, ExprResult &LHS,
+                                                ExprResult &RHS,
+                                                SourceLocation Loc,
+                                                unsigned OpaqueOpc) {
+  // This checking requires bools.
+  if (!S.getLangOpts().Bool) return;
+
+  // Check that left hand side is !something.
+  UnaryOperator *UO = dyn_cast<UnaryOperator>(LHS.get());
+  if (!UO || UO->getOpcode() != UO_LNot) return;
+
+  // Only check if the right hand side is non-bool arithmetic type.
+  if (RHS.get()->getType()->isBooleanType()) return;
+
+  // Make sure that the something in !something is not bool.
+  Expr *SubExpr = UO->getSubExpr()->IgnoreImpCasts();
+  if (SubExpr->getType()->isBooleanType()) return;
+
+  // Emit warning.
+  S.Diag(UO->getOperatorLoc(), diag::warn_logical_not_on_lhs_of_comparison)
+      << Loc;
+
+  // First note suggest !(x < y)
+  SourceLocation FirstOpen = SubExpr->getLocStart();
+  SourceLocation FirstClose = RHS.get()->getLocEnd();
+  FirstClose = S.getPreprocessor().getLocForEndOfToken(FirstClose);
+  S.Diag(UO->getOperatorLoc(), diag::note_logical_not_fix)
+      << FixItHint::CreateInsertion(FirstOpen, "(")
+      << FixItHint::CreateInsertion(FirstClose, ")");
+
+  // Second note suggests (!x) < y
+  SourceLocation SecondOpen = LHS.get()->getLocStart();
+  SourceLocation SecondClose = LHS.get()->getLocEnd();
+  SecondClose = S.getPreprocessor().getLocForEndOfToken(SecondClose);
+  S.Diag(UO->getOperatorLoc(), diag::note_logical_not_silence_with_parens)
+      << FixItHint::CreateInsertion(SecondOpen, "(")
+      << FixItHint::CreateInsertion(SecondClose, ")");
+}
+
 // C99 6.5.8, C++ [expr.rel]
 QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                     SourceLocation Loc, unsigned OpaqueOpc,
@@ -7270,6 +7309,7 @@ QualType Sema::CheckCompareOperands(Expr
   Expr *RHSStripped = RHS.get()->IgnoreParenImpCasts();
 
   checkEnumComparison(*this, Loc, LHS.get(), RHS.get());
+  diagnoseLogicalNotOnLHSofComparison(*this, LHS, RHS, Loc, OpaqueOpc);
 
   if (!LHSType->hasFloatingRepresentation() &&
       !(LHSType->isBlockPointerType() && IsRelational) &&

Added: cfe/trunk/test/SemaCXX/warn-logical-not-compare.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-logical-not-compare.cpp?rev=183688&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-logical-not-compare.cpp (added)
+++ cfe/trunk/test/SemaCXX/warn-logical-not-compare.cpp Mon Jun 10 13:52:07 2013
@@ -0,0 +1,112 @@
+// RUN: %clang_cc1 -fsyntax-only -Wlogical-not-parentheses -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wlogical-not-parentheses -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+bool getBool();
+int getInt();
+
+bool test1(int i1, int i2, bool b1, bool b2) {
+  bool ret;
+
+  ret = !i1 == i2;
+  // expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{10:10-10:10}:"("
+  // CHECK: fix-it:"{{.*}}":{10:18-10:18}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{10:9-10:9}:"("
+  // CHECK: fix-it:"{{.*}}":{10:12-10:12}:")"
+
+  ret = !i1 != i2;
+  //expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{21:10-21:10}:"("
+  // CHECK: fix-it:"{{.*}}":{21:18-21:18}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{21:9-21:9}:"("
+  // CHECK: fix-it:"{{.*}}":{21:12-21:12}:")"
+
+  ret = !i1 < i2;
+  //expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{32:10-32:10}:"("
+  // CHECK: fix-it:"{{.*}}":{32:17-32:17}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{32:9-32:9}:"("
+  // CHECK: fix-it:"{{.*}}":{32:12-32:12}:")"
+
+  ret = !i1 > i2;
+  //expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{43:10-43:10}:"("
+  // CHECK: fix-it:"{{.*}}":{43:17-43:17}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{43:9-43:9}:"("
+  // CHECK: fix-it:"{{.*}}":{43:12-43:12}:")"
+
+  ret = !i1 <= i2;
+  //expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{54:10-54:10}:"("
+  // CHECK: fix-it:"{{.*}}":{54:18-54:18}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{54:9-54:9}:"("
+  // CHECK: fix-it:"{{.*}}":{54:12-54:12}:")"
+
+  ret = !i1 >= i2;
+  //expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{65:10-65:10}:"("
+  // CHECK: fix-it:"{{.*}}":{65:18-65:18}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{65:9-65:9}:"("
+  // CHECK: fix-it:"{{.*}}":{65:12-65:12}:")"
+
+  ret = i1 == i2;
+  ret = i1 != i2;
+  ret = i1 < i2;
+  ret = i1 > i2;
+  ret = i1 <= i2;
+  ret = i1 >= i2;
+
+  // Warning silenced by parens.
+  ret = (!i1) == i2;
+  ret = (!i1) != i2;
+  ret = (!i1) < i2;
+  ret = (!i1) > i2;
+  ret = (!i1) <= i2;
+  ret = (!i1) >= i2;
+
+  ret = !b1 == b2;
+  ret = !b1 != b2;
+  ret = !b1 < b2;
+  ret = !b1 > b2;
+  ret = !b1 <= b2;
+  ret = !b1 >= b2;
+
+  ret = !getInt() == i1;
+  // expected-warning at -1 {{logical not is only applied to the left hand side of this comparison}}
+  // expected-note at -2 {{add parentheses after the '!' to evaluate the comparison first}}
+  // expected-note at -3 {{add parentheses around left hand side expression to silence this warning}}
+  // CHECK: to evaluate the comparison first
+  // CHECK: fix-it:"{{.*}}":{98:10-98:10}:"("
+  // CHECK: fix-it:"{{.*}}":{98:24-98:24}:")"
+  // CHECK: to silence this warning
+  // CHECK: fix-it:"{{.*}}":{98:9-98:9}:"("
+  // CHECK: fix-it:"{{.*}}":{98:18-98:18}:")"
+
+  ret = (!getInt()) == i1;
+  ret = !getBool() == b1;
+  return ret;
+}





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