[clang-tidy] Allow disabling integer narrowing conversions for cppcoreguidelines-narrowing-conversions

Differential Revision: https://reviews.llvm.org/D104018

clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp

@@ -35,6 +35,8 @@ auto hasAnyListedName(const std::string &Names) {
 NarrowingConversionsCheck::NarrowingConversionsCheck(StringRef Name,
                                                      ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
+      WarnOnIntegerNarrowingConversion(
+          Options.get("WarnOnIntegerNarrowingConversion", true)),
       WarnOnFloatingPointNarrowingConversion(
           Options.get("WarnOnFloatingPointNarrowingConversion", true)),
       WarnWithinTemplateInstantiation(
@@ -45,6 +47,8 @@ NarrowingConversionsCheck::NarrowingConversionsCheck(StringRef Name,
 
 void NarrowingConversionsCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "WarnOnIntegerNarrowingConversion",
+                WarnOnIntegerNarrowingConversion);
   Options.store(Opts, "WarnOnFloatingPointNarrowingConversion",
                 WarnOnFloatingPointNarrowingConversion);
   Options.store(Opts, "WarnWithinTemplateInstantiation",
@@ -294,34 +298,37 @@ void NarrowingConversionsCheck::handleIntegralCast(const ASTContext &Context,
                                                    SourceLocation SourceLoc,
                                                    const Expr &Lhs,
                                                    const Expr &Rhs) {
-  const BuiltinType *ToType = getBuiltinType(Lhs);
-  // From [conv.integral]p7.3.8:
-  // Conversions to unsigned integer is well defined so no warning is issued.
-  // "The resulting value is the smallest unsigned value equal to the source
-  // value modulo 2^n where n is the number of bits used to represent the
-  // destination type."
-  if (ToType->isUnsignedInteger())
-    return;
-  const BuiltinType *FromType = getBuiltinType(Rhs);
-
-  // With this option, we don't warn on conversions that have equivalent width
-  // in bits. eg. uint32 <-> int32.
-  if (!WarnOnEquivalentBitWidth) {
-    uint64_t FromTypeSize = Context.getTypeSize(FromType);
-    uint64_t ToTypeSize = Context.getTypeSize(ToType);
-    if (FromTypeSize == ToTypeSize)
+  if (WarnOnIntegerNarrowingConversion) {
+    const BuiltinType *ToType = getBuiltinType(Lhs);
+    // From [conv.integral]p7.3.8:
+    // Conversions to unsigned integer is well defined so no warning is issued.
+    // "The resulting value is the smallest unsigned value equal to the source
+    // value modulo 2^n where n is the number of bits used to represent the
+    // destination type."
+    if (ToType->isUnsignedInteger())
       return;
-  }
+    const BuiltinType *FromType = getBuiltinType(Rhs);
 
-  llvm::APSInt IntegerConstant;
-  if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
-    if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
-      diagNarrowIntegerConstantToSignedInt(SourceLoc, Lhs, Rhs, IntegerConstant,
-                                           Context.getTypeSize(FromType));
-    return;
+    // With this option, we don't warn on conversions that have equivalent width
+    // in bits. eg. uint32 <-> int32.
+    if (!WarnOnEquivalentBitWidth) {
+      uint64_t FromTypeSize = Context.getTypeSize(FromType);
+      uint64_t ToTypeSize = Context.getTypeSize(ToType);
+      if (FromTypeSize == ToTypeSize)
+        return;
+    }
+
+    llvm::APSInt IntegerConstant;
+    if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
+      if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
+        diagNarrowIntegerConstantToSignedInt(SourceLoc, Lhs, Rhs,
+                                             IntegerConstant,
+                                             Context.getTypeSize(FromType));
+      return;
+    }
+    if (!isWideEnoughToHold(Context, *FromType, *ToType))
+      diagNarrowTypeToSignedInt(SourceLoc, Lhs, Rhs);
   }
-  if (!isWideEnoughToHold(Context, *FromType, *ToType))
-    diagNarrowTypeToSignedInt(SourceLoc, Lhs, Rhs);
 }
 
 void NarrowingConversionsCheck::handleIntegralToBoolean(

clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.h

@@ -93,6 +93,7 @@ private:
   void handleBinaryOperator(const ASTContext &Context,
                             const BinaryOperator &Op);
 
+  const bool WarnOnIntegerNarrowingConversion;
   const bool WarnOnFloatingPointNarrowingConversion;
   const bool WarnWithinTemplateInstantiation;
   const bool WarnOnEquivalentBitWidth;

clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines-narrowing-conversions.rst

@@ -13,7 +13,8 @@ Guidelines, corresponding to rule ES.46. See
 https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es46-avoid-lossy-narrowing-truncating-arithmetic-conversions.
 
 We enforce only part of the guideline, more specifically, we flag narrowing conversions from:
- - an integer to a narrower integer (e.g. ``char`` to ``unsigned char``),
+ - an integer to a narrower integer (e.g. ``char`` to ``unsigned char``)
+   if WarnOnIntegerNarrowingConversion Option is set,
  - an integer to a narrower floating-point (e.g. ``uint64_t`` to ``float``),
  - a floating-point to an integer (e.g. ``double`` to ``int``),
  - a floating-point to a narrower floating-point (e.g. ``double`` to ``float``)
@@ -30,6 +31,11 @@ This check will flag:
 Options
 -------
 
+.. option:: WarnOnIntegerNarrowingConversion
+
+    When `true`, the check will warn on narrowing integer conversion
+    (e.g. ``int`` to ``size_t``). `true` by default.
+
 .. option:: WarnOnFloatingPointNarrowingConversion
 
     When `true`, the check will warn on narrowing floating point conversion

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-narrowing-conversions-narrowinginteger-option.cpp

@@ -0,0 +1,23 @@
+// RUN: %check_clang_tidy -check-suffix=DEFAULT %s \
+// RUN: cppcoreguidelines-narrowing-conversions %t -- \
+// RUN: -config='{CheckOptions: [{key: cppcoreguidelines-narrowing-conversions.WarnOnIntegerNarrowingConversion, value: true}]}'
+
+// RUN: %check_clang_tidy -check-suffix=DISABLED %s \
+// RUN: cppcoreguidelines-narrowing-conversions %t -- \
+// RUN: -config='{CheckOptions: [{key: cppcoreguidelines-narrowing-conversions.WarnOnIntegerNarrowingConversion, value: false}]}'
+
+void foo(unsigned long long value) {
+  int a = value;
+  // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:11: warning: narrowing conversion from 'unsigned long long' to signed type 'int' is implementation-defined [cppcoreguidelines-narrowing-conversions]
+  // DISABLED: No warning for integer narrowing conversions when WarnOnIntegerNarrowingConversion = false.
+  long long b = value;
+  // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:17: warning: narrowing conversion from 'unsigned long long' to signed type 'long long' is implementation-defined [cppcoreguidelines-narrowing-conversions]
+  // DISABLED: No warning for integer narrowing conversions when WarnOnIntegerNarrowingConversion = false.
+}
+
+void casting_float_to_bool_is_still_operational_when_integer_narrowing_is_disabled(float f) {
+  if (f) {
+    // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:7: warning: narrowing conversion from 'float' to 'bool' [cppcoreguidelines-narrowing-conversions]
+    // CHECK-MESSAGES-DISABLED: :[[@LINE-2]]:7: warning: narrowing conversion from 'float' to 'bool' [cppcoreguidelines-narrowing-conversions]
+  }
+}