https://github.com/Serosh-commits updated https://github.com/llvm/llvm-project/pull/176555
>From 3c8778cbb11c0bfcf69bdb5a9d2bc7780321b42e Mon Sep 17 00:00:00 2001 From: Serosh <[email protected]> Date: Sat, 17 Jan 2026 16:46:46 +0530 Subject: [PATCH 1/3] [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, 18 insertions(+), 10 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..ff6045552b0e4 100644 --- a/clang/lib/AST/ByteCode/Compiler.cpp +++ b/clang/lib/AST/ByteCode/Compiler.cpp @@ -1083,21 +1083,21 @@ 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; } - return false; + if (DiscardResult) + return this->emitPop(classifyPrim(E), E); + return true; } template <class Emitter> 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)); +} >From 9c5098c3f523b62ab35a84f932c750bf5756d145 Mon Sep 17 00:00:00 2001 From: Serosh <[email protected]> Date: Wed, 28 Jan 2026 22:02:32 +0530 Subject: [PATCH 2/3] [clang][bytecode] Fix stack corruption in pointer arithmetic discard (refactor to switch) --- clang/lib/AST/ByteCode/Compiler.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp index ff6045552b0e4..a0ef1009aa085 100644 --- a/clang/lib/AST/ByteCode/Compiler.cpp +++ b/clang/lib/AST/ByteCode/Compiler.cpp @@ -1080,13 +1080,16 @@ bool Compiler<Emitter>::VisitPointerArithBinOp(const BinaryOperator *E) { // Do the operation and optionally transform to // result pointer type. - if (Op == BO_Add) { + switch (Op) { + case BO_Add: if (!this->emitAddOffset(OffsetType, E)) return false; - } else if (Op == BO_Sub) { + break; + case BO_Sub: if (!this->emitSubOffset(OffsetType, E)) return false; - } else { + break; + default: return false; } >From 2ff620d707e72c66a62ff0ddae720b5211ba8440 Mon Sep 17 00:00:00 2001 From: Serosh <[email protected]> Date: Wed, 28 Jan 2026 22:54:57 +0530 Subject: [PATCH 3/3] Update test to expect comma operator warning --- clang/test/AST/ByteCode/gh176549.cpp | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/clang/test/AST/ByteCode/gh176549.cpp b/clang/test/AST/ByteCode/gh176549.cpp index b56f762b7ede4..42d055e9608c7 100644 --- a/clang/test/AST/ByteCode/gh176549.cpp +++ b/clang/test/AST/ByteCode/gh176549.cpp @@ -1,8 +1,7 @@ // 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)); + i = 1 > (a + 1, sizeof(a)); // expected-warning {{left operand of comma operator has no effect}} } _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
