llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Andrew Savonichev (asavonic) <details> <summary>Changes</summary> Clang warns about UB when a `reinterpret_cast` is dereferenced as an incompatible type: ``` long l; *reinterpret_cast<double*>(&l) // UB ``` However, the code was too strict and did not handle extra parens around a `reinterpret_cast`, so the following case was not diagnosed: ``` long l; *(reinterpret_cast<double*>(&l)) // UB, but no warning ``` The patch now skips ParenExpr when looking for a CXXReinterpretCastExpr to enable a diagnostic for the second case. --- Full diff: https://github.com/llvm/llvm-project/pull/157033.diff 2 Files Affected: - (modified) clang/lib/Sema/SemaExpr.cpp (+1-1) - (modified) clang/test/SemaCXX/reinterpret-cast.cpp (+3) ``````````diff diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index 8565b18078185..f7e02805ae9d0 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -14774,7 +14774,7 @@ static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK, QualType OpTy = Op->getType(); QualType Result; - if (isa<CXXReinterpretCastExpr>(Op)) { + if (isa<CXXReinterpretCastExpr>(Op->IgnoreParens())) { QualType OpOrigType = Op->IgnoreParenCasts()->getType(); S.CheckCompatibleReinterpretCast(OpOrigType, OpTy, /*IsDereference*/true, Op->getSourceRange()); diff --git a/clang/test/SemaCXX/reinterpret-cast.cpp b/clang/test/SemaCXX/reinterpret-cast.cpp index bfb808773b900..fdaa17a35eb8b 100644 --- a/clang/test/SemaCXX/reinterpret-cast.cpp +++ b/clang/test/SemaCXX/reinterpret-cast.cpp @@ -167,6 +167,9 @@ void dereference_reinterpret_cast() { (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}} + // Look through parens + (void)*(reinterpret_cast<double*>(&l)); // expected-warning {{dereference of type 'double *' that was reinterpret_cast from type 'long *' has undefined behavior}} + // TODO: add warning for tag types (void)reinterpret_cast<A&>(b); (void)*reinterpret_cast<A*>(&b); `````````` </details> https://github.com/llvm/llvm-project/pull/157033 _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
