Moved the logic for checking undefined behavior and its warnings into
CheckCompatibleReinterpretCast(). Also, cleaned up the test case a little.
On Thu, Apr 28, 2011 at 8:46 PM, Argyrios Kyrtzidis <[email protected]>wrote:
> One nitpick, I'd prefer that the DiagnosticLevel check is "close" in source
> code to the emission of the diagnostic.
> Could you insert the DiagnosticLevel check in the two places where the
> diagnostic is emitted or change isCompatibleReinterpretCast
> to a CheckCompatibleReinterpretCast function that does checks+warning
> ? isCompatibleReinterpretCast isn't used for anything else other than to
> emit the warning after all.
>
> On Apr 28, 2011, at 8:24 PM, Richard Trieu wrote:
>
> Added the level check. There's two warning messages, so I added a check
> for each one.
>
> On Thu, Apr 28, 2011 at 7:36 PM, Argyrios Kyrtzidis
> <[email protected]>wrote:
>
>> You don't check whether the warning is turned off to skip the checks
>> completely, something like
>>
>> Diags.getDiagnosticLevel(diag::warn_pointer_indirection_from_incompatible_type,
>> OpLoc) != Diagnostic::Ignored)
>>
>>
>> On Apr 28, 2011, at 7:16 PM, Richard Trieu wrote:
>>
>> Changes to support the white list in [basic.lval]p10. There should be a
>> corresponding test to each list item, except when those dealing with tag
>> types since we are skipping them for now.
>>
>> On Wed, Apr 27, 2011 at 6:11 PM, John McCall <[email protected]> wrote:
>>
>>> On Apr 27, 2011, at 6:07 PM, Richard Trieu wrote:
>>> > Is there a way that Clang can check if the warning is turned off and
>>> skip the expensive checking?
>>>
>>> Yes, you can check whether the current mapping for the diagnostic is
>>> still "ignore".
>>>
>>> > And did you mean the list in [basic.lval]p15? [basic.lval]p10 doesn't
>>> have a list.
>>>
>>> We're just looking at different standards. :) C++11's [basic.lval]p10 is
>>> just minor wording differences from C++03's [basic.lval]p15.
>>>
>>> John.
>>>
>>
>> <undefined-reinterpret-cast3.patch>
>> _______________________________________________
>>
>> cfe-commits mailing list
>> [email protected]
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>
>>
>>
> <undefined-reinterpret-cast4.patch>
>
>
>
Index: test/SemaCXX/reinterpret-cast.cpp
===================================================================
--- test/SemaCXX/reinterpret-cast.cpp (revision 130335)
+++ test/SemaCXX/reinterpret-cast.cpp (working copy)
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -ffreestanding %s
+// RUN: %clang_cc1 -fsyntax-only -verify -ffreestanding -Wundefined-reinterpret-cast %s
#include <stdint.h>
@@ -116,3 +116,155 @@
__attribute((ext_vector_type(4))) typedef float v4;
float& w(v4 &a) { return reinterpret_cast<float&>(a[1]); } // expected-error {{not allowed}}
}
+
+void dereference_reinterpret_cast() {
+ struct A {};
+ class B {};
+ A a;
+ B b;
+ long l;
+ double d;
+ float f;
+ char c;
+ unsigned char uc;
+ void* v_ptr;
+ (void)reinterpret_cast<double&>(l); // expected-warning {{reinterpret_cast from 'long' to 'double &' has undefined behavior}}
+ (void)*reinterpret_cast<double*>(&l); // expected-warning {{dereference of type 'double *' that was reinterpret_cast from type 'long *' has undefined behavior}}
+ (void)reinterpret_cast<double&>(f); // expected-warning {{reinterpret_cast from 'float' to 'double &' has undefined behavior}}
+ (void)*reinterpret_cast<double*>(&f); // expected-warning {{dereference of type 'double *' that was reinterpret_cast from type 'float *' has undefined behavior}}
+ (void)reinterpret_cast<float&>(l); // expected-warning {{reinterpret_cast from 'long' to 'float &' has undefined behavior}}
+ (void)*reinterpret_cast<float*>(&l); // expected-warning {{dereference of type 'float *' that was reinterpret_cast from type 'long *' has undefined behavior}}
+ (void)reinterpret_cast<float&>(d); // expected-warning {{reinterpret_cast from 'double' to 'float &' has undefined behavior}}
+ (void)*reinterpret_cast<float*>(&d); // expected-warning {{dereference of type 'float *' that was reinterpret_cast from type 'double *' has undefined behavior}}
+
+ // TODO: add warning for tag types
+ (void)reinterpret_cast<A&>(b);
+ (void)*reinterpret_cast<A*>(&b);
+ (void)reinterpret_cast<B&>(a);
+ (void)*reinterpret_cast<B*>(&a);
+
+ // Casting to itself is allowed
+ (void)reinterpret_cast<A&>(a);
+ (void)*reinterpret_cast<A*>(&a);
+ (void)reinterpret_cast<B&>(b);
+ (void)*reinterpret_cast<B*>(&b);
+ (void)reinterpret_cast<long&>(l);
+ (void)*reinterpret_cast<long*>(&l);
+ (void)reinterpret_cast<double&>(d);
+ (void)*reinterpret_cast<double*>(&d);
+ (void)reinterpret_cast<char&>(c);
+ (void)*reinterpret_cast<char*>(&c);
+
+ // Casting to and from chars are allowable
+ (void)reinterpret_cast<A&>(c);
+ (void)*reinterpret_cast<A*>(&c);
+ (void)reinterpret_cast<B&>(c);
+ (void)*reinterpret_cast<B*>(&c);
+ (void)reinterpret_cast<long&>(c);
+ (void)*reinterpret_cast<long*>(&c);
+ (void)reinterpret_cast<double&>(c);
+ (void)*reinterpret_cast<double*>(&c);
+ (void)reinterpret_cast<char&>(l);
+ (void)*reinterpret_cast<char*>(&l);
+ (void)reinterpret_cast<char&>(d);
+ (void)*reinterpret_cast<char*>(&d);
+ (void)reinterpret_cast<char&>(f);
+ (void)*reinterpret_cast<char*>(&f);
+
+ // Casting from void pointer.
+ (void)*reinterpret_cast<A*>(v_ptr);
+ (void)*reinterpret_cast<B*>(v_ptr);
+ (void)*reinterpret_cast<long*>(v_ptr);
+ (void)*reinterpret_cast<double*>(v_ptr);
+ (void)*reinterpret_cast<float*>(v_ptr);
+
+ // Casting to void pointer
+ (void)*reinterpret_cast<void*>(&a);
+ (void)*reinterpret_cast<void*>(&b);
+ (void)*reinterpret_cast<void*>(&l);
+ (void)*reinterpret_cast<void*>(&d);
+ (void)*reinterpret_cast<void*>(&f);
+}
+
+void reinterpret_cast_whitelist () {
+ // the dynamic type of the object
+ int a;
+ float b;
+ (void)reinterpret_cast<int&>(a);
+ (void)*reinterpret_cast<int*>(&a);
+ (void)reinterpret_cast<float&>(b);
+ (void)*reinterpret_cast<float*>(&b);
+
+ // a cv-qualified version of the dynamic object
+ (void)reinterpret_cast<const int&>(a);
+ (void)*reinterpret_cast<const int*>(&a);
+ (void)reinterpret_cast<volatile int&>(a);
+ (void)*reinterpret_cast<volatile int*>(&a);
+ (void)reinterpret_cast<const volatile int&>(a);
+ (void)*reinterpret_cast<const volatile int*>(&a);
+ (void)reinterpret_cast<const float&>(b);
+ (void)*reinterpret_cast<const float*>(&b);
+ (void)reinterpret_cast<volatile float&>(b);
+ (void)*reinterpret_cast<volatile float*>(&b);
+ (void)reinterpret_cast<const volatile float&>(b);
+ (void)*reinterpret_cast<const volatile float*>(&b);
+
+ // a type that is the signed or unsigned type corresponding to the dynamic
+ // type of the object
+ signed d;
+ unsigned e;
+ (void)reinterpret_cast<signed&>(d);
+ (void)*reinterpret_cast<signed*>(&d);
+ (void)reinterpret_cast<signed&>(e);
+ (void)*reinterpret_cast<signed*>(&e);
+ (void)reinterpret_cast<unsigned&>(d);
+ (void)*reinterpret_cast<unsigned*>(&d);
+ (void)reinterpret_cast<unsigned&>(e);
+ (void)*reinterpret_cast<unsigned*>(&e);
+
+ // a type that is the signed or unsigned type corresponding a cv-qualified
+ // version of the dynamic type the object
+ (void)reinterpret_cast<const signed&>(d);
+ (void)*reinterpret_cast<const signed*>(&d);
+ (void)reinterpret_cast<const signed&>(e);
+ (void)*reinterpret_cast<const signed*>(&e);
+ (void)reinterpret_cast<const unsigned&>(d);
+ (void)*reinterpret_cast<const unsigned*>(&d);
+ (void)reinterpret_cast<const unsigned&>(e);
+ (void)*reinterpret_cast<const unsigned*>(&e);
+ (void)reinterpret_cast<volatile signed&>(d);
+ (void)*reinterpret_cast<volatile signed*>(&d);
+ (void)reinterpret_cast<volatile signed&>(e);
+ (void)*reinterpret_cast<volatile signed*>(&e);
+ (void)reinterpret_cast<volatile unsigned&>(d);
+ (void)*reinterpret_cast<volatile unsigned*>(&d);
+ (void)reinterpret_cast<volatile unsigned&>(e);
+ (void)*reinterpret_cast<volatile unsigned*>(&e);
+ (void)reinterpret_cast<const volatile signed&>(d);
+ (void)*reinterpret_cast<const volatile signed*>(&d);
+ (void)reinterpret_cast<const volatile signed&>(e);
+ (void)*reinterpret_cast<const volatile signed*>(&e);
+ (void)reinterpret_cast<const volatile unsigned&>(d);
+ (void)*reinterpret_cast<const volatile unsigned*>(&d);
+ (void)reinterpret_cast<const volatile unsigned&>(e);
+ (void)*reinterpret_cast<const volatile unsigned*>(&e);
+
+ // an aggregate or union type that includes one of the aforementioned types
+ // among its members (including, recursively, a member of a subaggregate or
+ // contained union)
+ // TODO: checking is not implemented for tag types
+
+ // a type that is a (possible cv-qualified) base class type of the dynamic
+ // type of the object
+ // TODO: checking is not implemented for tag types
+
+ // a char or unsigned char type
+ (void)reinterpret_cast<char&>(a);
+ (void)*reinterpret_cast<char*>(&a);
+ (void)reinterpret_cast<unsigned char&>(a);
+ (void)*reinterpret_cast<unsigned char*>(&a);
+ (void)reinterpret_cast<char&>(b);
+ (void)*reinterpret_cast<char*>(&b);
+ (void)reinterpret_cast<unsigned char&>(b);
+ (void)*reinterpret_cast<unsigned char*>(&b);
+}
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td (revision 130335)
+++ include/clang/Basic/DiagnosticSemaKinds.td (working copy)
@@ -2637,6 +2637,10 @@
"indirection of non-volatile null pointer will be deleted, not trap">, InGroup<NullDereference>;
def note_indirection_through_null : Note<
"consider using __builtin_trap() or qualifying pointer with 'volatile'">;
+def warn_pointer_indirection_from_incompatible_type : Warning<
+ "dereference of type %1 that was reinterpret_cast from type %0 has undefined "
+ "behavior.">,
+ InGroup<DiagGroup<"undefined-reinterpret-cast">>, DefaultIgnore;
def err_assignment_requires_nonfragile_object : Error<
"cannot assign to class object in non-fragile ABI (%0 invalid)">;
@@ -2900,6 +2904,9 @@
def err_bad_static_cast_incomplete : Error<"%0 is an incomplete type">;
def err_bad_reinterpret_cast_reference : Error<
"reinterpret_cast of a %0 to %1 needs its address which is not allowed">;
+def warn_undefined_reinterpret_cast : Warning<
+ "reinterpret_cast from %0 to %1 has undefined behavior.">,
+ InGroup<DiagGroup<"undefined-reinterpret-cast">>, DefaultIgnore;
// These messages don't adhere to the pattern.
// FIXME: Display the path somehow better.
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h (revision 130335)
+++ include/clang/Sema/Sema.h (working copy)
@@ -2574,6 +2574,10 @@
ParsedType ObjectType,
bool EnteringContext);
+ // Checks that reinterpret casts don't have undefined behavior.
+ void CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,
+ bool IsDereference, SourceRange Range);
+
/// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's.
ExprResult ActOnCXXNamedCast(SourceLocation OpLoc,
tok::TokenKind Kind,
Index: lib/Sema/SemaCXXCast.cpp
===================================================================
--- lib/Sema/SemaCXXCast.cpp (revision 130335)
+++ lib/Sema/SemaCXXCast.cpp (working copy)
@@ -1288,7 +1288,62 @@
return TC_Success;
}
+// Checks for undefined behavior in reinterpret_cast.
+// The cases that is checked for is:
+// *reinterpret_cast<T*>(&a)
+// reinterpret_cast<T&>(a)
+// where accessing 'a' as type 'T' will result in undefined behavior.
+void Sema::CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,
+ bool IsDereference,
+ SourceRange Range) {
+ unsigned DiagID = IsDereference ?
+ diag::warn_pointer_indirection_from_incompatible_type :
+ diag::warn_undefined_reinterpret_cast;
+ if (Diags.getDiagnosticLevel(DiagID, SourceLocation()) ==
+ Diagnostic::Ignored) {
+ return;
+ }
+
+ QualType SrcTy, DestTy;
+ if (IsDereference) {
+ if (!SrcType->getAs<PointerType>() || !DestType->getAs<PointerType>()) {
+ return;
+ }
+ SrcTy = SrcType->getPointeeType();
+ DestTy = DestType->getPointeeType();
+ } else {
+ if (!DestType->getAs<ReferenceType>()) {
+ return;
+ }
+ SrcTy = SrcType;
+ DestTy = DestType->getPointeeType();
+ }
+
+ // Cast is compatible if the types are the same.
+ if (Context.hasSameUnqualifiedType(DestTy, SrcTy)) {
+ return;
+ }
+ // or one of the types is a char or void type
+ if (DestTy->isAnyCharacterType() || DestTy->isVoidType() ||
+ SrcTy->isAnyCharacterType() || SrcTy->isVoidType()) {
+ return;
+ }
+ // or one of the types is a tag type.
+ if (isa<TagType>(SrcTy) || isa<TagType>(DestTy)) {
+ return;
+ }
+
+ if ((SrcTy->isUnsignedIntegerType() && DestTy->isSignedIntegerType()) ||
+ (SrcTy->isSignedIntegerType() && DestTy->isUnsignedIntegerType())) {
+ if (Context.getTypeSize(DestTy) == Context.getTypeSize(SrcTy)) {
+ return;
+ }
+ }
+
+ Diag(Range.getBegin(), DiagID) << SrcType << DestType << Range;
+}
+
static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
QualType DestType, bool CStyle,
const SourceRange &OpRange,
@@ -1324,6 +1379,11 @@
return TC_NotApplicable;
}
+ if (!CStyle) {
+ Self.CheckCompatibleReinterpretCast(SrcType, DestType,
+ /*isDereference=*/false, OpRange);
+ }
+
// C++ 5.2.10p10: [...] a reference cast reinterpret_cast<T&>(x) has the
// same effect as the conversion *reinterpret_cast<T*>(&x) with the
// built-in & and * operators.
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp (revision 130335)
+++ lib/Sema/SemaExpr.cpp (working copy)
@@ -8393,7 +8393,13 @@
Op = ConvResult.take();
QualType OpTy = Op->getType();
QualType Result;
-
+
+ if (isa<CXXReinterpretCastExpr>(Op)) {
+ QualType OpOrigType = Op->IgnoreParenCasts()->getType();
+ S.CheckCompatibleReinterpretCast(OpOrigType, OpTy, /*IsDereference*/true,
+ Op->getSourceRange());
+ }
+
// Note that per both C89 and C99, indirection is always legal, even if OpTy
// is an incomplete type or void. It would be possible to warn about
// dereferencing a void pointer, but it's completely well-defined, and such a
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