[Lldb-commits] [lldb] [Reland] Detect against invalid variant index for LibStdC++ std::variant data formatters (PR #69614)
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Thu Oct 19 09:48:14 PDT 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: None (jeffreytan81)
<details>
<summary>Changes</summary>
This is relanding of https://github.com/llvm/llvm-project/pull/69253. `TestTemplatePackArgs.py` is passing now.
https://github.com/llvm/llvm-project/pull/68012/files added new data formatters for LibStdC++ std::variant.
However, this formatter can crash if std::variant's index field has invalid value (exceeds the number of template arguments).
This can happen if the current IP stops at a place std::variant is not initialized yet.
This patch fixes the crash by ensuring the index is a valid value and fix GetNthTemplateArgument() to make sure it is not crashing.
---
Full diff: https://github.com/llvm/llvm-project/pull/69614.diff
3 Files Affected:
- (modified) lldb/examples/synthetic/gnu_libstdcpp.py (+5)
- (modified) lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp (+2-1)
- (modified) lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py (+26)
``````````diff
diff --git a/lldb/examples/synthetic/gnu_libstdcpp.py b/lldb/examples/synthetic/gnu_libstdcpp.py
index 29c926167fb440c..f778065aaca3771 100644
--- a/lldb/examples/synthetic/gnu_libstdcpp.py
+++ b/lldb/examples/synthetic/gnu_libstdcpp.py
@@ -914,6 +914,11 @@ def get_variant_npos_value(index_byte_size):
if index == npos_value:
return " No Value"
+ # Invalid index can happen when the variant is not initialized yet.
+ template_arg_count = data_obj.GetType().GetNumberOfTemplateArguments()
+ if index >= template_arg_count:
+ return " <Invalid>"
+
active_type = data_obj.GetType().GetTemplateArgumentType(index)
return f" Active Type = {active_type.GetDisplayTypeName()} "
diff --git a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
index f1353db2631ddc6..df06ba0ed952af7 100644
--- a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -7183,7 +7183,8 @@ GetNthTemplateArgument(const clang::ClassTemplateSpecializationDecl *decl,
// (including the ones preceding the parameter pack).
const auto &pack = args[last_idx];
const size_t pack_idx = idx - last_idx;
- assert(pack_idx < pack.pack_size() && "parameter pack index out-of-bounds");
+ if (pack_idx >= pack.pack_size())
+ return nullptr;
return &pack.pack_elements()[pack_idx];
}
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
index 96a9c8d30c45b00..ba1641888b6f30f 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
@@ -71,3 +71,29 @@ def test_with_run_command(self):
substrs=["v_many_types_no_value = No Value"],
)
"""
+
+ @add_test_categories(["libstdcxx"])
+ def test_invalid_variant_index(self):
+ """Test LibStdC++ data formatter for std::variant with invalid index."""
+ self.build()
+
+ (self.target, self.process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+ self, "// break here", lldb.SBFileSpec("main.cpp", False)
+ )
+
+ lldbutil.continue_to_breakpoint(self.process, bkpt)
+
+ self.expect(
+ "frame variable v1",
+ substrs=["v1 = Active Type = int {", "Value = 12", "}"],
+ )
+
+ var_v1 = thread.frames[0].FindVariable("v1")
+ var_v1_raw_obj = var_v1.GetNonSyntheticValue()
+ index_obj = var_v1_raw_obj.GetChildMemberWithName("_M_index")
+ self.assertTrue(index_obj and index_obj.IsValid())
+
+ INVALID_INDEX = "100"
+ index_obj.SetValueFromCString(INVALID_INDEX)
+
+ self.expect("frame variable v1", substrs=["v1 = <Invalid>"])
``````````
</details>
https://github.com/llvm/llvm-project/pull/69614
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