llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Timm Baeder (tbaederr) <details> <summary>Changes</summary> ... if the elements are in different arrays. --- Full diff: https://github.com/llvm/llvm-project/pull/150407.diff 2 Files Affected: - (modified) clang/lib/AST/ByteCode/Interp.h (+19) - (modified) clang/test/AST/ByteCode/arrays.cpp (+21) ``````````diff diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h index b42c7665c3a35..a37cacedb627b 100644 --- a/clang/lib/AST/ByteCode/Interp.h +++ b/clang/lib/AST/ByteCode/Interp.h @@ -2383,6 +2383,25 @@ inline bool SubPtr(InterpState &S, CodePtr OpPC) { return false; } + // C++11 [expr.add]p6: + // Unless both pointers point to elements of the same array object, or + // one past the last element of the array object, the behavior is + // undefined. + if (!LHS.isRoot() && !RHS.isRoot() && LHS.isBlockPointer() && + RHS.isBlockPointer()) { + Pointer A = LHS; + if (LHS.isArrayElement()) + A = LHS.expand().getArray(); + + Pointer B = RHS; + if (RHS.isArrayElement()) + B = RHS.expand().getArray(); + + if (A != B) + S.CCEDiag(S.Current->getSource(OpPC), + diag::note_constexpr_pointer_subtraction_not_same_array); + } + if (LHS == RHS) { S.Stk.push<T>(); return true; diff --git a/clang/test/AST/ByteCode/arrays.cpp b/clang/test/AST/ByteCode/arrays.cpp index 2dd51c2fa6711..1329071c7188d 100644 --- a/clang/test/AST/ByteCode/arrays.cpp +++ b/clang/test/AST/ByteCode/arrays.cpp @@ -779,3 +779,24 @@ namespace DiscardedSubScriptExpr { return true; } } + +namespace SubPtr { + struct A {}; + struct B : A { int n; int m; }; + B a[3][3]; + constexpr int diff1 = &a[2] - &a[0]; + constexpr int diff2 = &a[1][3] - &a[1][0]; + constexpr int diff3 = &a[2][0] - &a[1][0]; // both-error {{must be initialized by a constant expression}} \ + // both-note {{subtracted pointers are not elements of the same array}} + struct S { + int a; + int b; + constexpr S() : a(1), b(2) {} + }; + + constexpr int f5() { // both-error {{never produces a constant expression}} + struct S s; + int d = &s.b - &s.a; // both-note {{subtracted pointers are not elements of the same array}} + return d; + } +} `````````` </details> https://github.com/llvm/llvm-project/pull/150407 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
