lebedev.ri updated this revision to Diff 102119. lebedev.ri edited the summary of this revision. lebedev.ri added a comment. This revision is now accepted and ready to land.
After further mail exchange, i will proceed to commit this as-is. No code changes, rebase before commit. Repository: rL LLVM https://reviews.llvm.org/D33102 Files: docs/ReleaseNotes.rst lib/Sema/SemaCast.cpp test/Sema/warn-cast-qual.c test/SemaCXX/warn-cast-qual.cpp
Index: test/SemaCXX/warn-cast-qual.cpp =================================================================== --- /dev/null +++ test/SemaCXX/warn-cast-qual.cpp @@ -0,0 +1,140 @@ +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fsyntax-only -Wcast-qual -verify %s + +#include <stdint.h> + +// do *NOT* warn on const_cast<>() +// use clang-tidy's cppcoreguidelines-pro-type-const-cast for that. +void foo_ptr() { + const char *const ptr = 0; + char *t0 = const_cast<char *>(ptr); // no warning + + volatile char *ptr2 = 0; + char *t1 = const_cast<char *>(ptr2); // no warning + + const volatile char *ptr3 = 0; + char *t2 = const_cast<char *>(ptr3); // no warning +} + +void cstr() { + void* p0 = (void*)(const void*)"txt"; // expected-warning {{cast from 'const void *' to 'void *' drops const qualifier}} + void* p1 = (void*)"txt"; // FIXME + char* p2 = (char*)"txt"; // expected-warning {{cast from 'const char *' to 'char *' drops const qualifier}} +} + +void foo_0() { + const int a = 0; + + const int &a0 = a; // no warning + const int &a1 = (const int &)a; // no warning + + int &a2 = (int &)a; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + const int &a3 = (int &)a; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + int &a4 = (int &)((const int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + int &a5 = (int &)((int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + const int &a6 = (int &)((int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + const int &a7 = (int &)((const int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + const int &a8 = (const int &)((int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} +} + +void foo_1() { + volatile int a = 0; + + volatile int &a0 = a; // no warning + volatile int &a1 = (volatile int &)a; // no warning + + int &a2 = (int &)a; // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + volatile int &a3 = (int &)a; // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + int &a4 = (int &)((volatile int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + int &a5 = (int &)((int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + volatile int &a6 = (int &)((int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + volatile int &a7 = (int &)((volatile int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} + volatile int &a8 = (volatile int &)((int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}} +} + +void foo_2() { + const volatile int a = 0; + + const volatile int &a0 = a; // no warning + const volatile int &a1 = (const volatile int &)a; // no warning + + int &a2 = (int &)a; // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + const volatile int &a3 = (int &)a; // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + int &a4 = (int &)((const volatile int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + int &a5 = (int &)((int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + const volatile int &a6 = (int &)((int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + const volatile int &a7 = (int &)((const volatile int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} + const volatile int &a8 = (const volatile int &)((int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}} +} + +void bar_0() { + const int *_a = 0; + const int **a = &_a; + + int **a0 = (int **)((const int **)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + int **a1 = (int **)((int **)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + + // const int **a2 = (int **)((int **)a); + // const int **a3 = (int **)((const int **)a); + + const int **a4 = (const int **)((int **)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'int **' to 'const int **' must have all intermediate pointers const qualified to be safe}} + const int **a5 = (const int **)((const int **)a); // no warning +} + +void bar_1() { + const int *_a = 0; + const int *&a = _a; + + int *&a0 = (int *&)((const int *&)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + int *&a1 = (int *&)((int *&)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + + // const int *&a2 = (int *&)((int *&)a); + // const int *&a3 = (int *&)((const int *&)a); + + const int *&a4 = (const int *&)((int *&)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'int *' to 'const int *&' must have all intermediate pointers const qualified to be safe}} + const int *&a5 = (const int *&)((const int *&)a); // no warning +} + +void baz_0() { + struct C { + void A() {} + void B() const {} + }; + + const C S; + S.B(); + + ((C &)S).B(); // expected-warning {{cast from 'const C' to 'C &' drops const qualifier}} + ((C &)S).A(); // expected-warning {{cast from 'const C' to 'C &' drops const qualifier}} + + ((C *)&S)->B(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}} + ((C *)&S)->A(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}} +} + +void baz_1() { + struct C { + const int a; + int b; + + C() : a(0) {} + }; + + { + C S; + S.b = 0; + + (int &)(S.a) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + (int &)(S.b) = 0; // no warning + + *(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + *(int *)(&S.b) = 0; // no warning + } + { + const C S; + + (int &)(S.a) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + (int &)(S.b) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}} + + *(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + *(int *)(&S.b) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + } +} Index: test/Sema/warn-cast-qual.c =================================================================== --- test/Sema/warn-cast-qual.c +++ test/Sema/warn-cast-qual.c @@ -1,4 +1,5 @@ // RUN: %clang_cc1 -triple x86_64-unknown-unknown -fsyntax-only -Wcast-qual -verify %s +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -x c++ -fsyntax-only -Wcast-qual -verify %s #include <stdint.h> @@ -26,4 +27,34 @@ const char **charptrptrc; char **charptrptr = (char **)charptrptrc; // expected-warning {{cast from 'const char *' to 'char *' drops const qualifier}} + + const char *constcharptr; + char *charptr = (char *)constcharptr; // expected-warning {{cast from 'const char *' to 'char *' drops const qualifier}} + const char *constcharptr2 = (char *)constcharptr; // expected-warning {{cast from 'const char *' to 'char *' drops const qualifier}} + const char *charptr2 = (char *)charptr; // no warning +} + +void bar_0() { + struct C { + const int a; + int b; + }; + + const struct C S = {0, 0}; + + *(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + *(int *)(&S.b) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} +} + +void bar_1() { + struct C { + const int a; + int b; + }; + + struct C S = {0, 0}; + S.b = 0; // no warning + + *(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} + *(int *)(&S.b) = 0; // no warning } Index: lib/Sema/SemaCast.cpp =================================================================== --- lib/Sema/SemaCast.cpp +++ lib/Sema/SemaCast.cpp @@ -143,6 +143,9 @@ }; } +static void DiagnoseCastQual(Sema &Self, const ExprResult &SrcExpr, + QualType DestType); + // The Try functions attempt a specific way of casting. If they succeed, they // return TC_Success. If their way of casting is not appropriate for the given // arguments, they return TC_NotApplicable and *may* set diag to a diagnostic @@ -427,6 +430,10 @@ /// the same kind of pointer (plain or to-member). Unlike the Sema function, /// this one doesn't care if the two pointers-to-member don't point into the /// same class. This is because CastsAwayConstness doesn't care. +/// And additionally, it handles C++ references. If both the types are +/// references, then their pointee types are returned, +/// else if only one of them is reference, it's pointee type is returned, +/// and the other type is returned as-is. static bool UnwrapDissimilarPointerTypes(QualType& T1, QualType& T2) { const PointerType *T1PtrType = T1->getAs<PointerType>(), *T2PtrType = T2->getAs<PointerType>(); @@ -475,6 +482,26 @@ return true; } + const LValueReferenceType *T1RefType = T1->getAs<LValueReferenceType>(), + *T2RefType = T2->getAs<LValueReferenceType>(); + if (T1RefType && T2RefType) { + T1 = T1RefType->getPointeeType(); + T2 = T2RefType->getPointeeType(); + return true; + } + + if (T1RefType) { + T1 = T1RefType->getPointeeType(); + // T2 = T2; + return true; + } + + if (T2RefType) { + // T1 = T1; + T2 = T2RefType->getPointeeType(); + return true; + } + return false; } @@ -503,11 +530,13 @@ // the rules are non-trivial. So first we construct Tcv *...cv* as described // in C++ 5.2.11p8. assert((SrcType->isAnyPointerType() || SrcType->isMemberPointerType() || - SrcType->isBlockPointerType()) && + SrcType->isBlockPointerType() || + DestType->isLValueReferenceType()) && "Source type is not pointer or pointer to member."); assert((DestType->isAnyPointerType() || DestType->isMemberPointerType() || - DestType->isBlockPointerType()) && - "Destination type is not pointer or pointer to member."); + DestType->isBlockPointerType() || + DestType->isLValueReferenceType()) && + "Destination type is not pointer or pointer to member, or reference."); QualType UnwrappedSrcType = Self.Context.getCanonicalType(SrcType), UnwrappedDestType = Self.Context.getCanonicalType(DestType); @@ -2177,6 +2206,8 @@ void CastOperation::CheckCXXCStyleCast(bool FunctionalStyle, bool ListInitialization) { + assert(Self.getLangOpts().CPlusPlus); + // Handle placeholders. if (isPlaceholder()) { // C-style casts can resolve __unknown_any types. @@ -2580,30 +2611,42 @@ if (Kind == CK_BitCast) checkCastAlign(); +} + +/// DiagnoseCastQual - Warn whenever casts discards a qualifiers, be it either +/// const, volatile or both. +static void DiagnoseCastQual(Sema &Self, const ExprResult &SrcExpr, + QualType DestType) { + if (SrcExpr.isInvalid()) + return; + + QualType SrcType = SrcExpr.get()->getType(); + if (!((SrcType->isAnyPointerType() && DestType->isAnyPointerType()) || + DestType->isLValueReferenceType())) + return; - // -Wcast-qual QualType TheOffendingSrcType, TheOffendingDestType; Qualifiers CastAwayQualifiers; - if (SrcType->isAnyPointerType() && DestType->isAnyPointerType() && - CastsAwayConstness(Self, SrcType, DestType, true, false, - &TheOffendingSrcType, &TheOffendingDestType, - &CastAwayQualifiers)) { - int qualifiers = -1; - if (CastAwayQualifiers.hasConst() && CastAwayQualifiers.hasVolatile()) { - qualifiers = 0; - } else if (CastAwayQualifiers.hasConst()) { - qualifiers = 1; - } else if (CastAwayQualifiers.hasVolatile()) { - qualifiers = 2; - } - // This is a variant of int **x; const int **y = (const int **)x; - if (qualifiers == -1) - Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual2) << - SrcType << DestType; - else - Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual) << - TheOffendingSrcType << TheOffendingDestType << qualifiers; + if (!CastsAwayConstness(Self, SrcType, DestType, true, false, + &TheOffendingSrcType, &TheOffendingDestType, + &CastAwayQualifiers)) + return; + + int qualifiers = -1; + if (CastAwayQualifiers.hasConst() && CastAwayQualifiers.hasVolatile()) { + qualifiers = 0; + } else if (CastAwayQualifiers.hasConst()) { + qualifiers = 1; + } else if (CastAwayQualifiers.hasVolatile()) { + qualifiers = 2; } + // This is a variant of int **x; const int **y = (const int **)x; + if (qualifiers == -1) + Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual2) + << SrcType << DestType; + else + Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual) + << TheOffendingSrcType << TheOffendingDestType << qualifiers; } ExprResult Sema::BuildCStyleCastExpr(SourceLocation LPLoc, @@ -2624,6 +2667,9 @@ if (Op.SrcExpr.isInvalid()) return ExprError(); + // -Wcast-qual + DiagnoseCastQual(Op.Self, Op.SrcExpr, Op.DestType); + return Op.complete(CStyleCastExpr::Create(Context, Op.ResultType, Op.ValueKind, Op.Kind, Op.SrcExpr.get(), &Op.BasePath, CastTypeInfo, LPLoc, RPLoc)); Index: docs/ReleaseNotes.rst =================================================================== --- docs/ReleaseNotes.rst +++ docs/ReleaseNotes.rst @@ -52,6 +52,9 @@ Improvements to Clang's diagnostics ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +- -Wcast-qual was implemented for C++. C-style casts are now properly + diagnosed. + - -Wunused-lambda-capture warns when a variable explicitly captured by a lambda is not used in the body of the lambda.
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