rnk updated this revision to Diff 91653.
rnk marked an inline comment as done.
rnk added a comment.
- Actually make this warning off by default
https://reviews.llvm.org/D30923
Files:
include/clang/Basic/DiagnosticGroups.td
include/clang/Basic/DiagnosticSemaKinds.td
lib/Sema/SemaChecking.cpp
test/SemaCXX/warn-bitfield-enum-conversion.cpp
Index: test/SemaCXX/warn-bitfield-enum-conversion.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/warn-bitfield-enum-conversion.cpp
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-windows-msvc -verify %s -Wbitfield-enum-conversion
+
+enum TwoBits { Hi1 = 3 } two_bits;
+enum TwoBitsSigned { Lo2 = -2, Hi2 = 1 } two_bits_signed;
+enum ThreeBits { Hi3 = 7 } three_bits;
+enum ThreeBitsSigned { Lo4 = -4, Hi4 = 3 } three_bits_signed;
+enum TwoBitsFixed : unsigned { Hi5 = 3 } two_bits_fixed;
+
+struct Foo {
+ unsigned two_bits : 2;
+ int two_bits_signed : 2;
+ unsigned three_bits : 3;
+ int three_bits_signed : 3;
+
+ ThreeBits three_bits_enum : 3;
+};
+
+void f() {
+ Foo f;
+
+ f.two_bits = two_bits;
+ f.two_bits = two_bits_signed; // expected-warning {{negative enumerators}}
+ f.two_bits = three_bits; // expected-warning {{not wide enough}}
+ f.two_bits = three_bits_signed; // expected-warning {{negative enumerators}} expected-warning {{not wide enough}}
+ f.two_bits = two_bits_fixed;
+
+ f.two_bits_signed = two_bits; // expected-warning {{needs an extra bit}}
+ f.two_bits_signed = two_bits_signed;
+ f.two_bits_signed = three_bits; // expected-warning {{not wide enough}}
+ f.two_bits_signed = three_bits_signed; // expected-warning {{not wide enough}}
+
+ f.three_bits = two_bits;
+ f.three_bits = two_bits_signed; // expected-warning {{negative enumerators}}
+ f.three_bits = three_bits;
+ f.three_bits = three_bits_signed; // expected-warning {{negative enumerators}}
+
+ f.three_bits_signed = two_bits;
+ f.three_bits_signed = two_bits_signed;
+ f.three_bits_signed = three_bits; // expected-warning {{needs an extra bit}}
+ f.three_bits_signed = three_bits_signed;
+
+ f.three_bits_enum = three_bits; // expected-warning {{needs an extra bit}}
+}
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -8729,13 +8729,42 @@
return false;
Expr *OriginalInit = Init->IgnoreParenImpCasts();
+ unsigned FieldWidth = Bitfield->getBitWidthValue(S.Context);
llvm::APSInt Value;
- if (!OriginalInit->EvaluateAsInt(Value, S.Context, Expr::SE_AllowSideEffects))
+ if (!OriginalInit->EvaluateAsInt(Value, S.Context,
+ Expr::SE_AllowSideEffects)) {
+ // The RHS is not constant. If the RHS has an enum type, make sure the
+ // bitfield is wide enough to hold all the values of the enum without
+ // truncation.
+ if (const auto *EnumTy = OriginalInit->getType()->getAs<EnumType>()) {
+ EnumDecl *ED = EnumTy->getDecl();
+ bool SignedBitfield = BitfieldType->isSignedIntegerType();
+
+ // Check if this might store negative values into an unsigned bitfield.
+ if (!SignedBitfield && ED->getNumNegativeBits() > 0) {
+ S.Diag(InitLoc, diag::warn_unsigned_bitfield_assigned_signed_enum)
+ << Bitfield << ED;
+ }
+
+ // Check for sufficient width.
+ if (ED->getNumPositiveBits() > FieldWidth ||
+ ED->getNumNegativeBits() > FieldWidth) {
+ S.Diag(InitLoc, diag::warn_bitfield_too_small_for_enum)
+ << Bitfield << ED;
+ } else if (SignedBitfield && ED->getNumPositiveBits() == FieldWidth) {
+ // If the bitfield type is signed and the positive field widths are
+ // equal, values with the high bit set will become negative, which is
+ // usually unintended.
+ S.Diag(InitLoc, diag::warn_signed_bitfield_enum_conversion)
+ << Bitfield << ED;
+ }
+ }
+
return false;
+ }
unsigned OriginalWidth = Value.getBitWidth();
- unsigned FieldWidth = Bitfield->getBitWidthValue(S.Context);
if (!Value.isSigned() || Value.isNegative())
if (UnaryOperator *UO = dyn_cast<UnaryOperator>(OriginalInit))
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -4908,6 +4908,17 @@
def warn_anon_bitfield_width_exceeds_type_width : Warning<
"width of anonymous bit-field (%0 bits) exceeds width of its type; value "
"will be truncated to %1 bit%s1">, InGroup<BitFieldWidth>;
+def warn_bitfield_too_small_for_enum: Warning<
+ "bit-field %0 is not wide enough to store all enumerators of enum type %1">,
+ InGroup<BitFieldEnumConversion>, DefaultIgnore;
+def warn_unsigned_bitfield_assigned_signed_enum: Warning<
+ "assigning value of signed enum type %1 to unsigned bit-field %0; "
+ "negative enumerators of enum %1 will be converted to positive values">,
+ InGroup<BitFieldEnumConversion>, DefaultIgnore;
+def warn_signed_bitfield_enum_conversion: Warning<
+ "signed bit-field %0 needs an extra bit to represent the largest positive "
+ "values of enum type %1">,
+ InGroup<BitFieldEnumConversion>, DefaultIgnore;
def warn_missing_braces : Warning<
"suggest braces around initialization of subobject">,
Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -34,6 +34,7 @@
def GNUBinaryLiteral : DiagGroup<"gnu-binary-literal">;
def GNUCompoundLiteralInitializer : DiagGroup<"gnu-compound-literal-initializer">;
def BitFieldConstantConversion : DiagGroup<"bitfield-constant-conversion">;
+def BitFieldEnumConversion : DiagGroup<"bitfield-enum-conversion">;
def BitFieldWidth : DiagGroup<"bitfield-width">;
def ConstantConversion :
DiagGroup<"constant-conversion", [ BitFieldConstantConversion ] >;
@@ -606,6 +607,7 @@
[BoolConversion,
ConstantConversion,
EnumConversion,
+ BitFieldEnumConversion,
FloatConversion,
Shorten64To32,
IntConversion,
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