[Diagnostics] Diagnose misused xor as pow

Summary:
Motivation:
https://twitter.com/jfbastien/status/1139298419988549632
https://twitter.com/mikemx7f/status/1139335901790625793
https://codesearch.isocpp.org/cgi-bin/cgi_ppsearch?q=10+%5E&search=Search

Reviewers: jfb, rsmith, regehr, aaron.ballman

Reviewed By: aaron.ballman

Subscribers: lebedev.ri, Quuxplusone, erik.pilkington, riccibruno, dexonsmith, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63423

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@369217 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 46c29698f7a21d218cb8bf907c0d23f22e78fc04..fc5931d7025bf84c3785824c4f335ce8c508e9c2 100644 (file)
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -512,6 +512,7 @@ def CompareDistinctPointerType : DiagGroup<"compare-distinct-pointer-types">;
 def GNUUnionCast : DiagGroup<"gnu-union-cast">;
 def GNUVariableSizedTypeNotAtEnd : DiagGroup<"gnu-variable-sized-type-not-at-end">;
 def Varargs : DiagGroup<"varargs">;
+def XorUsedAsPow : DiagGroup<"xor-used-as-pow">;
 
 def Unsequenced : DiagGroup<"unsequenced">;
 // GCC name for -Wunsequenced

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 0522f2a2ed2dfbe7f0c956fe26292c43b5f0c1e3..e704cb0b9b67c670f7a0b0f5f49693a7f409566e 100644 (file)
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3326,6 +3326,15 @@ def warn_address_of_reference_bool_conversion : Warning<
   "code; pointer may be assumed to always convert to true">,
   InGroup<UndefinedBoolConversion>;
 
+def warn_xor_used_as_pow_base_extra : Warning<
+  "result of '%0' is %1; did you mean '%2' (%3)?">,
+  InGroup<XorUsedAsPow>;
+def warn_xor_used_as_pow_base : Warning<
+  "result of '%0' is %1; did you mean '%2'?">,
+  InGroup<XorUsedAsPow>;
+def note_xor_used_as_pow_silence : Note<
+  "replace expression with '%0' to silence this warning">;
+
 def warn_null_pointer_compare : Warning<
     "comparison of %select{address of|function|array}0 '%1' %select{not |}2"
     "equal to a null pointer is always %select{true|false}2">,

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index b218ad1f66cf1ea9df710f3235a773b990fa9343..e2ff34a8a794481d045b70c34f17900efb678a52 100644 (file)
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -11011,6 +11011,107 @@ QualType Sema::CheckVectorCompareOperands(ExprResult &LHS, ExprResult &RHS,
   return GetSignedVectorType(vType);
 }
 
+static void diagnoseXorMisusedAsPow(Sema &S, ExprResult &LHS, ExprResult &RHS,
+                                    SourceLocation Loc) {
+  // Do not diagnose macros.
+  if (Loc.isMacroID())
+    return;
+
+  bool Negative = false;
+  const auto *LHSInt = dyn_cast<IntegerLiteral>(LHS.get());
+  const auto *RHSInt = dyn_cast<IntegerLiteral>(RHS.get());
+
+  if (!LHSInt)
+    return;
+  if (!RHSInt) {
+    // Check negative literals.
+    if (const auto *UO = dyn_cast<UnaryOperator>(RHS.get())) {
+      if (UO->getOpcode() != UO_Minus)
+        return;
+      RHSInt = dyn_cast<IntegerLiteral>(UO->getSubExpr());
+      if (!RHSInt)
+        return;
+      Negative = true;
+    } else {
+      return;
+    }
+  }
+
+  if (LHSInt->getValue().getBitWidth() != RHSInt->getValue().getBitWidth())
+    return;
+
+  CharSourceRange ExprRange = CharSourceRange::getCharRange(
+      LHSInt->getBeginLoc(), S.getLocForEndOfToken(RHSInt->getLocation()));
+  llvm::StringRef ExprStr =
+      Lexer::getSourceText(ExprRange, S.getSourceManager(), S.getLangOpts());
+
+  CharSourceRange XorRange =
+      CharSourceRange::getCharRange(Loc, S.getLocForEndOfToken(Loc));
+  llvm::StringRef XorStr =
+      Lexer::getSourceText(XorRange, S.getSourceManager(), S.getLangOpts());
+  // Do not diagnose if xor keyword/macro is used.
+  if (XorStr == "xor")
+    return;
+
+  const llvm::APInt &LeftSideValue = LHSInt->getValue();
+  const llvm::APInt &RightSideValue = RHSInt->getValue();
+  const llvm::APInt XorValue = LeftSideValue ^ RightSideValue;
+
+  std::string LHSStr = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(LHSInt->getSourceRange()),
+      S.getSourceManager(), S.getLangOpts());
+  std::string RHSStr = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(RHSInt->getSourceRange()),
+      S.getSourceManager(), S.getLangOpts());
+
+  int64_t RightSideIntValue = RightSideValue.getSExtValue();
+  if (Negative) {
+    RightSideIntValue = -RightSideIntValue;
+    RHSStr = "-" + RHSStr;
+  }
+
+  StringRef LHSStrRef = LHSStr;
+  StringRef RHSStrRef = RHSStr;
+  // Do not diagnose binary, hexadecimal, octal literals.
+  if (LHSStrRef.startswith("0b") || LHSStrRef.startswith("0B") ||
+      RHSStrRef.startswith("0b") || RHSStrRef.startswith("0B") ||
+      LHSStrRef.startswith("0x") || LHSStrRef.startswith("0X") ||
+      RHSStrRef.startswith("0x") || RHSStrRef.startswith("0X") ||
+      (LHSStrRef.size() > 1 && LHSStrRef.startswith("0")) ||
+      (RHSStrRef.size() > 1 && RHSStrRef.startswith("0")))
+    return;
+
+  if (LeftSideValue == 2 && RightSideIntValue >= 0) {
+    std::string SuggestedExpr = "1 << " + RHSStr;
+    bool Overflow = false;
+    llvm::APInt One = (LeftSideValue - 1);
+    llvm::APInt PowValue = One.sshl_ov(RightSideValue, Overflow);
+    if (Overflow) {
+      if (RightSideIntValue < 64)
+        S.Diag(Loc, diag::warn_xor_used_as_pow_base)
+            << ExprStr << XorValue.toString(10, true) << ("1LL << " + RHSStr)
+            << FixItHint::CreateReplacement(ExprRange, "1LL << " + RHSStr);
+      else
+         // TODO: 2 ^ 64 - 1
+        return;
+    } else {
+      S.Diag(Loc, diag::warn_xor_used_as_pow_base_extra)
+          << ExprStr << XorValue.toString(10, true) << SuggestedExpr
+          << PowValue.toString(10, true)
+          << FixItHint::CreateReplacement(
+                 ExprRange, (RightSideIntValue == 0) ? "1" : SuggestedExpr);
+    }
+
+    S.Diag(Loc, diag::note_xor_used_as_pow_silence) << ("0x2 ^ " + RHSStr);
+  } else if (LeftSideValue == 10) {
+    std::string SuggestedValue = "1e" + std::to_string(RightSideIntValue);
+    S.Diag(Loc, diag::warn_xor_used_as_pow_base)
+        << ExprStr << XorValue.toString(10, true) << SuggestedValue
+        << FixItHint::CreateReplacement(ExprRange, SuggestedValue);
+    S.Diag(Loc, diag::note_xor_used_as_pow_silence) << ("0xA ^ " + RHSStr);
+  }
+}
+
 QualType Sema::CheckVectorLogicalOperands(ExprResult &LHS, ExprResult &RHS,
                                           SourceLocation Loc) {
   // Ensure that either both operands are of the same vector type, or
@@ -11054,6 +11155,9 @@ inline QualType Sema::CheckBitwiseOperands(ExprResult &LHS, ExprResult &RHS,
   if (Opc == BO_And)
     diagnoseLogicalNotOnLHSofCheck(*this, LHS, RHS, Loc, Opc);
 
+  if (Opc == BO_Xor)
+    diagnoseXorMisusedAsPow(*this, LHS, RHS, Loc);
+
   ExprResult LHSResult = LHS, RHSResult = RHS;
   QualType compType = UsualArithmeticConversions(LHSResult, RHSResult,
                                                  IsCompAssign);
@@ -17640,4 +17744,4 @@ ExprResult Sema::ActOnObjCAvailabilityCheckExpr(
 
   return new (Context)
       ObjCAvailabilityCheckExpr(Version, AtLoc, RParen, Context.BoolTy);
-}
+}
\ No newline at end of file

diff --git a/test/SemaCXX/warn-xor-as-pow.cpp b/test/SemaCXX/warn-xor-as-pow.cpp
new file mode 100644 (file)
index 0000000..8ff32a2
--- /dev/null
+++ b/test/SemaCXX/warn-xor-as-pow.cpp
@@ -0,0 +1,105 @@
+// RUN: %clang_cc1 -x c -fsyntax-only -verify -Wxor-used-as-pow %s
+// RUN: %clang_cc1 -x c -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x c -fsyntax-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+// RUN: %clang_cc1 -x c++ -fsyntax-only -verify -Wxor-used-as-pow %s
+// RUN: %clang_cc1 -x c++ -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x c++ -fsyntax-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+#define FOOBAR(x, y) (x * y)
+#define XOR(x, y) (x ^ y)
+#define TWO 2
+#define TEN 10
+#define TWO_ULL 2ULL
+#define EPSILON 10 ^ -300
+
+#define flexor 7
+
+#ifdef __cplusplus
+constexpr long long operator"" _xor(unsigned long long v) { return v; }
+
+constexpr long long operator"" _0b(unsigned long long v) { return v; }
+constexpr long long operator"" _0X(unsigned long long v) { return v; }
+#else
+#define xor    ^ // iso646.h
+#endif
+
+void test(unsigned a, unsigned b) {
+  unsigned res;
+  res = a ^ 5;
+  res = 2 ^ b;
+  res = a ^ b;
+  res = 2 ^ -1;
+  res = 2 ^ 0; // expected-warning {{result of '2 ^ 0' is 2; did you mean '1 << 0' (1)?}}
+               // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:14}:"1"
+               // expected-note@-2 {{replace expression with '0x2 ^ 0' to silence this warning}}
+  res = 2 ^ 1; // expected-warning {{result of '2 ^ 1' is 3; did you mean '1 << 1' (2)?}}
+               // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:14}:"1 << 1"
+               // expected-note@-2 {{replace expression with '0x2 ^ 1' to silence this warning}}
+  res = 2 ^ 2; // expected-warning {{result of '2 ^ 2' is 0; did you mean '1 << 2' (4)?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:14}:"1 << 2"
+  // expected-note@-2 {{replace expression with '0x2 ^ 2' to silence this warning}}
+  res = 2 ^ 8; // expected-warning {{result of '2 ^ 8' is 10; did you mean '1 << 8' (256)?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:14}:"1 << 8"
+  // expected-note@-2 {{replace expression with '0x2 ^ 8' to silence this warning}}
+  res = TWO ^ 8; // expected-warning {{result of 'TWO ^ 8' is 10; did you mean '1 << 8' (256)?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:16}:"1 << 8"
+  // expected-note@-2 {{replace expression with '0x2 ^ 8' to silence this warning}}
+  res = 2 ^ 16; // expected-warning {{result of '2 ^ 16' is 18; did you mean '1 << 16' (65536)?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1 << 16"
+  // expected-note@-2 {{replace expression with '0x2 ^ 16' to silence this warning}}
+  res = 2 ^ TEN; // expected-warning {{result of '2 ^ TEN' is 8; did you mean '1 << TEN' (1024)?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:16}:"1 << TEN"
+  // expected-note@-2 {{replace expression with '0x2 ^ TEN' to silence this warning}}
+  res = 0x2 ^ 16;
+  res = 2 xor 16;
+
+  res = 2 ^ 0x4;
+  res = 2 ^ 04;
+  res = 0x2 ^ 10;
+  res = 0X2 ^ 10;
+  res = 02 ^ 10;
+  res = FOOBAR(2, 16);
+  res = 0b10 ^ 16;
+  res = 0B10 ^ 16;
+  res = 2 ^ 0b100;
+  res = XOR(2, 16);
+  unsigned char two = 2;
+  res = two ^ 16;
+  res = TWO_ULL ^ 16;
+  res = 2 ^ 32; // expected-warning {{result of '2 ^ 32' is 34; did you mean '1LL << 32'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1LL << 32"
+  // expected-note@-2 {{replace expression with '0x2 ^ 32' to silence this warning}}
+  res = 2 ^ 64;
+
+  res = EPSILON;
+  res = 10 ^ 0; // expected-warning {{result of '10 ^ 0' is 10; did you mean '1e0'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1e0"
+  // expected-note@-2 {{replace expression with '0xA ^ 0' to silence this warning}}
+  res = 10 ^ 1; // expected-warning {{result of '10 ^ 1' is 11; did you mean '1e1'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1e1"
+  // expected-note@-2 {{replace expression with '0xA ^ 1' to silence this warning}}
+  res = 10 ^ 2; // expected-warning {{result of '10 ^ 2' is 8; did you mean '1e2'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1e2"
+  // expected-note@-2 {{replace expression with '0xA ^ 2' to silence this warning}}
+  res = 10 ^ 4; // expected-warning {{result of '10 ^ 4' is 14; did you mean '1e4'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:15}:"1e4"
+  // expected-note@-2 {{replace expression with '0xA ^ 4' to silence this warning}}
+  res = 10 ^ 10; // expected-warning {{result of '10 ^ 10' is 0; did you mean '1e10'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:16}:"1e10"
+  // expected-note@-2 {{replace expression with '0xA ^ 10' to silence this warning}}
+  res = TEN ^ 10; // expected-warning {{result of 'TEN ^ 10' is 0; did you mean '1e10'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:17}:"1e10"
+  // expected-note@-2 {{replace expression with '0xA ^ 10' to silence this warning}}
+  res = 10 ^ 100; // expected-warning {{result of '10 ^ 100' is 110; did you mean '1e100'?}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:9-[[@LINE-1]]:17}:"1e100"
+  // expected-note@-2 {{replace expression with '0xA ^ 100' to silence this warning}}
+  res = 0xA ^ 10;
+  res = 10 xor 10;
+#ifdef __cplusplus
+  res = 10 ^ 5_xor;
+  res = 10_xor ^ 5;
+  res = 10 ^ 5_0b;
+  res = 10_0X ^ 5;
+#endif
+}