Index: clang/docs/ReleaseNotes.rst =================================================================== --- clang/docs/ReleaseNotes.rst +++ clang/docs/ReleaseNotes.rst @@ -101,9 +101,13 @@ - ``-Wformat`` now recognizes ``%b`` for the ``printf``/``scanf`` family of functions and ``%B`` for the ``printf`` family of functions. Fixes `Issue 56885: `_. -- ``-Wbitfield-constant-conversion`` now diagnoses implicit truncation when 1 is - assigned to a 1-bit signed integer bitfield. This fixes - `Issue 53253 `_. +- Introduced ``-Wsingle-bit-bitfield-constant-conversion``, grouped under + ``-Wbitfield-constant-conversion``, which diagnoses implicit truncation when + ``1`` is assigned to a 1-bit signed integer bitfield. This fixes + `Issue 53253 `_. To reduce + potential false positives, this diagnostic will not diagnose use of the + ``true`` macro (from ``>`) in C language mode despite the macro + being defined to expand to ``1``. - ``-Wincompatible-function-pointer-types`` now defaults to an error in all C language modes. It may be downgraded to a warning with ``-Wno-error=incompatible-function-pointer-types`` or disabled entirely with Index: clang/include/clang/Basic/DiagnosticGroups.td =================================================================== --- clang/include/clang/Basic/DiagnosticGroups.td +++ clang/include/clang/Basic/DiagnosticGroups.td @@ -47,7 +47,10 @@ CXXPre14CompatBinaryLiteral, GNUBinaryLiteral]>; def GNUCompoundLiteralInitializer : DiagGroup<"gnu-compound-literal-initializer">; -def BitFieldConstantConversion : DiagGroup<"bitfield-constant-conversion">; +def SingleBitBitFieldConstantConversion : + DiagGroup<"single-bit-bitfield-constant-conversion">; +def BitFieldConstantConversion : DiagGroup<"bitfield-constant-conversion", + [SingleBitBitFieldConstantConversion]>; def BitFieldEnumConversion : DiagGroup<"bitfield-enum-conversion">; def BitFieldWidth : DiagGroup<"bitfield-width">; def CompoundTokenSplitByMacro : DiagGroup<"compound-token-split-by-macro">; Index: clang/include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- clang/include/clang/Basic/DiagnosticSemaKinds.td +++ clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -3846,6 +3846,9 @@ def warn_impcast_integer_precision_constant : Warning< "implicit conversion from %2 to %3 changes value from %0 to %1">, InGroup; +def warn_impcast_single_bit_bitield_precision_constant : Warning< + "implicit truncation from %2 to a one-bit wide bit-field changes value from " + "%0 to %1">, InGroup; def warn_impcast_bitfield_precision_constant : Warning< "implicit truncation from %2 to bit-field changes value from %0 to %1">, InGroup; Index: clang/lib/Sema/SemaChecking.cpp =================================================================== --- clang/lib/Sema/SemaChecking.cpp +++ clang/lib/Sema/SemaChecking.cpp @@ -13047,6 +13047,18 @@ unsigned OriginalWidth = Value.getBitWidth(); + // In C, the macro 'true' from stdbool.h will evaluate to '1'; To reduce + // false positives where the user is demonstrating they intend to use the + // bit-field as a Boolean, check to see if the value is 1 and we're assigning + // to a one-bit bit-field to see if the value came from a macro named 'true'. + bool OneAssignedToOneBitBitfield = FieldWidth == 1 && Value == 1; + if (OneAssignedToOneBitBitfield && !S.LangOpts.CPlusPlus) { + SourceLocation MaybeMacroLoc = OriginalInit->getBeginLoc(); + if (S.SourceMgr.isInSystemMacro(MaybeMacroLoc) && + S.findMacroSpelling(MaybeMacroLoc, "true")) + return false; + } + if (!Value.isSigned() || Value.isNegative()) if (UnaryOperator *UO = dyn_cast(OriginalInit)) if (UO->getOpcode() == UO_Minus || UO->getOpcode() == UO_Not) @@ -13067,9 +13079,11 @@ std::string PrettyValue = toString(Value, 10); std::string PrettyTrunc = toString(TruncatedValue, 10); - S.Diag(InitLoc, diag::warn_impcast_bitfield_precision_constant) - << PrettyValue << PrettyTrunc << OriginalInit->getType() - << Init->getSourceRange(); + S.Diag(InitLoc, OneAssignedToOneBitBitfield + ? diag::warn_impcast_single_bit_bitield_precision_constant + : diag::warn_impcast_bitfield_precision_constant) + << PrettyValue << PrettyTrunc << OriginalInit->getType() + << Init->getSourceRange(); return true; } Index: clang/test/CXX/drs/dr6xx.cpp =================================================================== --- clang/test/CXX/drs/dr6xx.cpp +++ clang/test/CXX/drs/dr6xx.cpp @@ -911,9 +911,9 @@ namespace dr675 { // dr675: dup 739 template struct A { T n : 1; }; #if __cplusplus >= 201103L - static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to bit-field changes value from 1 to -1}} - static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to bit-field changes value from 1 to -1}} - static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to bit-field changes value from 1 to -1}} + static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1}} + static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1}} + static_assert(A{1}.n < 0, ""); // expected-warning {{implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1}} #endif } Index: clang/test/Sema/constant-conversion.c =================================================================== --- clang/test/Sema/constant-conversion.c +++ clang/test/Sema/constant-conversion.c @@ -1,4 +1,7 @@ -// RUN: %clang_cc1 -fsyntax-only -verify -triple x86_64-apple-darwin %s +// RUN: %clang_cc1 -fsyntax-only -ffreestanding -verify=expected,one-bit -triple x86_64-apple-darwin %s +// RUN: %clang_cc1 -fsyntax-only -ffreestanding -Wno-single-bit-bitfield-constant-conversion -verify -triple x86_64-apple-darwin %s + +#include // This file tests -Wconstant-conversion, a subcategory of -Wconversion // which is on by default. @@ -19,12 +22,14 @@ int b : 1; // The only valid values are 0 and -1. } s; - s.b = -3; // expected-warning {{implicit truncation from 'int' to bit-field changes value from -3 to -1}} - s.b = -2; // expected-warning {{implicit truncation from 'int' to bit-field changes value from -2 to 0}} - s.b = -1; // no-warning - s.b = 0; // no-warning - s.b = 1; // expected-warning {{implicit truncation from 'int' to bit-field changes value from 1 to -1}} - s.b = 2; // expected-warning {{implicit truncation from 'int' to bit-field changes value from 2 to 0}} + s.b = -3; // expected-warning {{implicit truncation from 'int' to bit-field changes value from -3 to -1}} + s.b = -2; // expected-warning {{implicit truncation from 'int' to bit-field changes value from -2 to 0}} + s.b = -1; // no-warning + s.b = 0; // no-warning + s.b = 1; // one-bit-warning {{implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1}} + s.b = true; // no-warning (we suppress it manually to reduce false positives) + s.b = false; // no-warning + s.b = 2; // expected-warning {{implicit truncation from 'int' to bit-field changes value from 2 to 0}} } enum Test2 { K_zero, K_one }; Index: clang/test/SemaCXX/constant-conversion.cpp =================================================================== --- clang/test/SemaCXX/constant-conversion.cpp +++ clang/test/SemaCXX/constant-conversion.cpp @@ -22,3 +22,12 @@ char ok3 = true ? 0 : 99999 + 1; char ok4 = true ? 0 : nines() + 1; } + +void test_bitfield() { + struct S { + int one_bit : 1; + } s; + + s.one_bit = 1; // expected-warning {{implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1}} + s.one_bit = true; // no-warning +}