Author: Anton Bikineev Date: 2021-04-14T01:01:40+02:00 New Revision: 69545154cc28a0a7f813174253c6cb428666eb3a
URL: https://github.com/llvm/llvm-project/commit/69545154cc28a0a7f813174253c6cb428666eb3a DIFF: https://github.com/llvm/llvm-project/commit/69545154cc28a0a7f813174253c6cb428666eb3a.diff LOG: [Sema] Move 'char-expression-as-unsigned < 0' into a separate diagnostic This change splits '-Wtautological-unsigned-zero-compare' by reporting char-expressions-interpreted-as-unsigned under a separate diagnostic '-Wtautological-unsigned-char-zero-compare'. This is beneficial for projects that want to enable '-Wtautological-unsigned-zero-compare' but at the same time want to keep code portable for platforms with char being signed or unsigned, such as Chromium. Differential Revision: https://reviews.llvm.org/D99808 Added: clang/test/Sema/tautological-unsigned-char-zero-compare.cc Modified: clang/include/clang/Basic/DiagnosticGroups.td clang/include/clang/Basic/DiagnosticSemaKinds.td clang/lib/Sema/SemaChecking.cpp Removed: ################################################################################ diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td index 85f798013a3d..e202645d1f2b 100644 --- a/clang/include/clang/Basic/DiagnosticGroups.td +++ b/clang/include/clang/Basic/DiagnosticGroups.td @@ -591,11 +591,13 @@ def SwiftNameAttribute : DiagGroup<"swift-name-attribute">; def IntInBoolContext : DiagGroup<"int-in-bool-context">; def TautologicalTypeLimitCompare : DiagGroup<"tautological-type-limit-compare">; def TautologicalUnsignedZeroCompare : DiagGroup<"tautological-unsigned-zero-compare">; +def TautologicalUnsignedCharZeroCompare : DiagGroup<"tautological-unsigned-char-zero-compare">; def TautologicalUnsignedEnumZeroCompare : DiagGroup<"tautological-unsigned-enum-zero-compare">; // For compatibility with GCC. Tautological comparison warnings for constants // that are an extremal value of the type. def TypeLimits : DiagGroup<"type-limits", [TautologicalTypeLimitCompare, TautologicalUnsignedZeroCompare, + TautologicalUnsignedCharZeroCompare, TautologicalUnsignedEnumZeroCompare]>; // Additional tautological comparison warnings based on the expression, not // only on its type. diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index af7eea06f6f5..afef86ab5890 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -6784,6 +6784,10 @@ def warn_unsigned_always_true_comparison : Warning< "result of comparison of %select{%3|unsigned expression}0 %2 " "%select{unsigned expression|%3}0 is always %4">, InGroup<TautologicalUnsignedZeroCompare>, DefaultIgnore; +def warn_unsigned_char_always_true_comparison : Warning< + "result of comparison of %select{%3|char expression}0 %2 " + "%select{char expression|%3}0 is always %4, since char is interpreted as " + "unsigned">, InGroup<TautologicalUnsignedCharZeroCompare>, DefaultIgnore; def warn_unsigned_enum_always_true_comparison : Warning< "result of comparison of %select{%3|unsigned enum expression}0 %2 " "%select{unsigned enum expression|%3}0 is always %4">, diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index fa5e184d2864..7b6e0541aa4d 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -11446,11 +11446,14 @@ static bool CheckTautologicalComparison(Sema &S, BinaryOperator *E, << OtherIsBooleanDespiteType << *Result << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange()); } else { - unsigned Diag = (isKnownToHaveUnsignedValue(OriginalOther) && Value == 0) - ? (HasEnumType(OriginalOther) - ? diag::warn_unsigned_enum_always_true_comparison - : diag::warn_unsigned_always_true_comparison) - : diag::warn_tautological_constant_compare; + bool IsCharTy = OtherT.withoutLocalFastQualifiers() == S.Context.CharTy; + unsigned Diag = + (isKnownToHaveUnsignedValue(OriginalOther) && Value == 0) + ? (HasEnumType(OriginalOther) + ? diag::warn_unsigned_enum_always_true_comparison + : IsCharTy ? diag::warn_unsigned_char_always_true_comparison + : diag::warn_unsigned_always_true_comparison) + : diag::warn_tautological_constant_compare; S.Diag(E->getOperatorLoc(), Diag) << RhsConstant << OtherT << E->getOpcodeStr() << OS.str() << *Result diff --git a/clang/test/Sema/tautological-unsigned-char-zero-compare.cc b/clang/test/Sema/tautological-unsigned-char-zero-compare.cc new file mode 100644 index 000000000000..4d14954b3213 --- /dev/null +++ b/clang/test/Sema/tautological-unsigned-char-zero-compare.cc @@ -0,0 +1,39 @@ +// RUN: %clang_cc1 -fsyntax-only \ +// RUN: -fno-signed-char \ +// RUN: -Wtautological-unsigned-zero-compare \ +// RUN: -Wtautological-unsigned-char-zero-compare \ +// RUN: -verify=unsigned %s +// RUN: %clang_cc1 -fsyntax-only \ +// RUN: -Wtautological-unsigned-zero-compare \ +// RUN: -Wtautological-unsigned-char-zero-compare \ +// RUN: -verify=signed %s + +void f(char c, unsigned char uc, signed char cc) { + if (c < 0) + return; + // unsigned-warning@-2 {{comparison of char expression < 0 is always false, since char is interpreted as unsigned}} + if (uc < 0) + return; + // unsigned-warning@-2 {{comparison of unsigned expression < 0 is always false}} + // signed-warning@-3 {{comparison of unsigned expression < 0 is always false}} + if (cc < 0) + return; + // Promoted to integer expressions should not warn. + if (c - 4 < 0) + return; +} + +void ref(char &c, unsigned char &uc, signed char &cc) { + if (c < 0) + return; + // unsigned-warning@-2 {{comparison of char expression < 0 is always false, since char is interpreted as unsigned}} + if (uc < 0) + return; + // unsigned-warning@-2 {{comparison of unsigned expression < 0 is always false}} + // signed-warning@-3 {{comparison of unsigned expression < 0 is always false}} + if (cc < 0) + return; + // Promoted to integer expressions should not warn. + if (c - 4 < 0) + return; +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
