https://github.com/DavidSpickett created https://github.com/llvm/llvm-project/pull/152993
https://github.com/llvm/llvm-project/pull/147835 made changes that caused libstdc++ std::string tests to fail: ``` ====================================================================== FAIL: test_unavailable_summary_libstdcxx_dwo (TestDataFormatterStdString.StdStringDataFormatterTestCase) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1805, in test_method return attrvalue(self) File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py", line 223, in test_unavailable_summary_libstdcxx self.do_test_summary_unavailable() File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py", line 213, in do_test_summary_unavailable self.assertEqual(summary, "Summary Unavailable", "No summary for bad value") AssertionError: '(null)' != 'Summary Unavailable' - (null) + Summary Unavailable : No summary for bad value Config=aarch64-/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang ---------------------------------------------------------------------- ``` This test constructs an invalid std::string by starting with a null pointer. Somehow this improvement in Clang uncovered a bug in the formatter. The formatter tries to access `_M_p` and checked whether the resulting ValueObjectSP was null, but not that it did not contain an error value. I think that error value can be there if you are able to access one part of the path, `_M_dataplus`, but another part fails. Since the layout looks like this: ``` struct _Alloc_hider : { pointer _M_p; // The actual data. }; _Alloc_hider _M_dataplus; void _M_data(pointer __p) { _M_dataplus._M_p = __p; } ``` So I think we were able to read `_M_dataplus` just by offset, but then failed because it contains, or points to something containing nulls or a null pointer. Or perhaps an error value means we know what the class member is, but could not read from it. I found this by comparing with the libcxx formatter, so I've copied the same handling from there to fix the issue. >From facece685fe39b8fbeca3261183a5aeac8dcee4c Mon Sep 17 00:00:00 2001 From: David Spickett <david.spick...@linaro.org> Date: Mon, 11 Aug 2025 10:43:37 +0000 Subject: [PATCH] [lldb] Fix libstdc++ std::string formatter after #147835 https://github.com/llvm/llvm-project/pull/147835 made changes that caused libstdc++ std::string tests to fail: ``` ====================================================================== FAIL: test_unavailable_summary_libstdcxx_dwo (TestDataFormatterStdString.StdStringDataFormatterTestCase) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1805, in test_method return attrvalue(self) File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py", line 223, in test_unavailable_summary_libstdcxx self.do_test_summary_unavailable() File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py", line 213, in do_test_summary_unavailable self.assertEqual(summary, "Summary Unavailable", "No summary for bad value") AssertionError: '(null)' != 'Summary Unavailable' - (null) + Summary Unavailable : No summary for bad value Config=aarch64-/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang ---------------------------------------------------------------------- ``` This test constructs an invalid std::string by starting with a null pointer. Somehow this improvement in Clang uncovered a bug in the formatter. The formatter tries to access `_M_p` and checked whether the resulting ValueObjectSP was null, but not that it did not contain an error value. I think that error value can be there if you are able to access one part of the path, `_M_dataplus`, but another part fails. Since the layout looks like this: ``` struct _Alloc_hider : { pointer _M_p; // The actual data. }; _Alloc_hider _M_dataplus; void _M_data(pointer __p) { _M_dataplus._M_p = __p; } ``` So I think we were able to read `_M_dataplus` just by offset, but then failed because it contains, or points to something containing nulls or a null pointer. Or perhaps an error value means we know what the class member is, but could not read from it. I found this by comparing with the libcxx formatter, so I've copied the same handling from there to fix the issue. --- lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp index 595e835b37df9..f4a695e036999 100644 --- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp +++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp @@ -241,10 +241,11 @@ VectorIteratorSyntheticFrontEnd::GetIndexOfChildWithName(ConstString name) { bool lldb_private::formatters::LibStdcppStringSummaryProvider( ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) { ValueObjectSP ptr = valobj.GetChildAtNamePath({"_M_dataplus", "_M_p"}); - if (!ptr) - return false; + if (!ptr || !ptr->GetError().Success()) + stream << "Summary Unavailable"; + else + stream << ptr->GetSummaryAsCString(); - stream << ptr->GetSummaryAsCString(); return true; } _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
