https://github.com/MrEven132 created https://github.com/llvm/llvm-project/pull/219395
`Evaluate_DW_OP_piece` returned early for a zero-sized piece before removing its source location from the expression stack. A later non-empty piece could then assemble the correct composite buffer while the stale source remained on the stack and was returned instead. Consume the source stack entry when a zero-sized piece has one, while still contributing no bytes to the composite. Add a unit test covering a zero-sized register piece followed by a non-empty register piece. Fixes #209099 >From 1596755cc9687b57c9dbff23de6a577dab8ac419 Mon Sep 17 00:00:00 2001 From: MrEven132 <[email protected]> Date: Fri, 28 Aug 2026 14:58:24 +0800 Subject: [PATCH] [lldb] Consume the source of zero-sized DW_OP_piece operations --- lldb/source/Expression/DWARFExpression.cpp | 7 ++++++- .../unittests/Expression/DWARFExpressionTest.cpp | 16 ++++++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp index d22634d63e875..3d238e0952b76 100644 --- a/lldb/source/Expression/DWARFExpression.cpp +++ b/lldb/source/Expression/DWARFExpression.cpp @@ -1112,8 +1112,13 @@ static llvm::Error Evaluate_DW_OP_piece(EvalContext &eval_ctx, // Reset for the next piece. eval_ctx.loc_desc_kind = Memory; - if (piece_byte_size == 0) + if (piece_byte_size == 0) { + // A zero-sized piece contributes no data, but it still consumes its source + // location description. + if (!eval_ctx.stack.empty()) + eval_ctx.stack.pop_back(); return llvm::Error::success(); + } Value curr_piece; diff --git a/lldb/unittests/Expression/DWARFExpressionTest.cpp b/lldb/unittests/Expression/DWARFExpressionTest.cpp index aa8e17a88cc34..4f0c86bfaa426 100644 --- a/lldb/unittests/Expression/DWARFExpressionTest.cpp +++ b/lldb/unittests/Expression/DWARFExpressionTest.cpp @@ -2265,6 +2265,22 @@ TEST_F(DWARFExpressionMockProcessTest, DW_OP_piece_file_addr) { ExpectHostAddress({0x11, 0x22})); } +TEST_F(DWARFExpressionMockProcessTest, DW_OP_piece_zero_size) { + TestContext test_ctx; + ASSERT_TRUE(CreateTestContext(&test_ctx, "i386-pc-linux", + RegisterValue(uint32_t{0x44332211}))); + + ExecutionContext exe_ctx(test_ctx.process_sp); + MockDwarfDelegate delegate = MockDwarfDelegate::Dwarf5(); + + // The zero-sized r3 piece contributes no bytes, but it must still consume + // its register location before the four-byte r0 piece is assembled. + EXPECT_THAT_EXPECTED( + Evaluate({DW_OP_reg3, DW_OP_piece, 0, DW_OP_reg0, DW_OP_piece, 4}, {}, + &delegate, &exe_ctx, test_ctx.reg_ctx_sp.get()), + ExpectHostAddress({0x11, 0x22, 0x33, 0x44})); +} + class DWARFExpressionMockProcessTestWithAArch : public DWARFExpressionMockProcessTest { public: _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
