https://github.com/Serosh-commits created https://github.com/llvm/llvm-project/pull/176555
The bytecode compiler was ignoring the DiscardResult flag in VisitPointerArithBinOp , causing pointer addition and subtraction results to persist on the stack when they should have been popped (e.g., in comma expressions). This led to stack corruption and assertion failures in subsequent operations that encountered an unexpected pointer on the stack. This patch refactors the unified addition/subtraction logic to ensure the result is properly popped when DiscardResult is true. Fixes #176549 >From c01243bcbc79068bce0a3f7ad5a3779d53ea97c1 Mon Sep 17 00:00:00 2001 From: Serosh <[email protected]> Date: Sat, 17 Jan 2026 16:46:46 +0530 Subject: [PATCH] [clang][bytecode] Fix stack corruption in pointer arithmetic discard In VisitPointerArithBinOp, the result of pointer addition or subtraction was always left on the stack, even if the result was intended to be discarded (e.g. in a comma expression). This led to stack corruption where subsequent operations would find an unexpected pointer on the stack, causing an assertion failure in the InterpStack. This patch ensures that we correctly respect the DiscardResult flag for pointer arithmetic operations. Fixes #176549 --- clang/lib/AST/ByteCode/Compiler.cpp | 20 +++++++++++--------- clang/test/AST/ByteCode/gh176549.cpp | 8 ++++++++ 2 files changed, 19 insertions(+), 9 deletions(-) create mode 100644 clang/test/AST/ByteCode/gh176549.cpp diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp index 21f8db06919ed..66b0cc4b5f6ab 100644 --- a/clang/lib/AST/ByteCode/Compiler.cpp +++ b/clang/lib/AST/ByteCode/Compiler.cpp @@ -1083,20 +1083,22 @@ bool Compiler<Emitter>::VisitPointerArithBinOp(const BinaryOperator *E) { if (Op == BO_Add) { if (!this->emitAddOffset(OffsetType, E)) return false; - - if (classifyPrim(E) != PT_Ptr) - return this->emitDecayPtr(PT_Ptr, classifyPrim(E), E); - return true; - } - if (Op == BO_Sub) { + } else if (Op == BO_Sub) { if (!this->emitSubOffset(OffsetType, E)) return false; + } else { + return false; + } - if (classifyPrim(E) != PT_Ptr) - return this->emitDecayPtr(PT_Ptr, classifyPrim(E), E); - return true; + if (classifyPrim(E) != PT_Ptr) { + if (!this->emitDecayPtr(PT_Ptr, classifyPrim(E), E)) + return false; } + if (DiscardResult) + return this->emitPop(classifyPrim(E), E); + return true; + return false; } diff --git a/clang/test/AST/ByteCode/gh176549.cpp b/clang/test/AST/ByteCode/gh176549.cpp new file mode 100644 index 0000000000000..b56f762b7ede4 --- /dev/null +++ b/clang/test/AST/ByteCode/gh176549.cpp @@ -0,0 +1,8 @@ +// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -verify %s +// expected-no-diagnostics + +const char a[4] = "abc"; +void foo() { + int i = 0; + i = 1 > (a + 1, sizeof(a)); +} _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
