caio/clang-p2996
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[lldb][DataFormatters] Adjust retrieval of unordered_map element type (#140256)

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A user ran into an issue where the libc++ `std::unordered_map` formatter
fails because it can't deduce the `element_type`. That happens because
the `node_type` is a forwad declaration. And, in fact, dsymutil stripped
the definition for `std::__1::__hash_node<...>` for a particular
instantiation. While I'm still unclear whether this is a dsymutil bug,
this patch works around said issue by getting the element type from the
`__table_` member.

Drive-by:
- Set the `m_element_type` in `Update`, which is where the other members
are initialized

I don't have a reduced example of this unfortunately. But the crux of
the issue is that `std::__1::__hash_node<...>` only has a forward
declaration in the dsym. Then trying to call `GetTypeTemplateArgument`
on that `CompilerType` fails. And even if the definition was present in
the dsym it seems like we're stopped in a context where the CU only had
a forward declaration DIE for that type and the `node_type` never ends
up being completed with the definition that lives in another CU.

rdar://150813798
This commit is contained in:
Michael Buch
2025-05-20 09:44:26 +01:00
committed by GitHub
parent 32a1b6a70b
commit 034eaeddc3
1 changed files with 12 additions and 11 deletions
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23
lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
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@@ -44,7 +44,7 @@ public:
private:
CompilerType GetNodeType();
CompilerType GetElementType(CompilerType node_type);
CompilerType GetElementType(CompilerType table_type);
llvm::Expected<size_t> CalculateNumChildrenImpl(ValueObject &table);
CompilerType m_element_type;
@@ -98,8 +98,8 @@ static bool isUnorderedMap(ConstString type_name) {
}
CompilerType lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::
GetElementType(CompilerType node_type) {
CompilerType element_type = node_type.GetTypeTemplateArgument(0);
GetElementType(CompilerType table_type) {
auto element_type = table_type.GetTypedefedType().GetTypeTemplateArgument(0);
// This synthetic provider is used for both unordered_(multi)map and
// unordered_(multi)set. For unordered_map, the element type has an
@@ -114,7 +114,7 @@ CompilerType lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::
element_type.GetFieldAtIndex(0, name, nullptr, nullptr, nullptr);
CompilerType actual_type = field_type.GetTypedefedType();
if (isStdTemplate(actual_type.GetTypeName(), "pair"))
element_type = actual_type;
return actual_type;
}
return element_type;
@@ -161,13 +161,6 @@ lldb::ValueObjectSP lldb_private::formatters::
ValueObjectSP value_sp = node_sp->GetChildMemberWithName("__value_");
ValueObjectSP hash_sp = node_sp->GetChildMemberWithName("__hash_");
if (!hash_sp || !value_sp) {
if (!m_element_type) {
m_node_type = GetNodeType();
if (!m_node_type)
return nullptr;
m_element_type = GetElementType(m_node_type);
}
node_sp = m_next_element->Cast(m_node_type.GetPointerType())
->Dereference(error);
if (!node_sp || error.Fail())
@@ -271,6 +264,14 @@ lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::Update() {
if (!table_sp)
return lldb::ChildCacheState::eRefetch;
m_node_type = GetNodeType();
if (!m_node_type)
return lldb::ChildCacheState::eRefetch;
m_element_type = GetElementType(table_sp->GetCompilerType());
if (!m_element_type)
return lldb::ChildCacheState::eRefetch;
ValueObjectSP tree_sp = GetTreePointer(*table_sp);
if (!tree_sp)
return lldb::ChildCacheState::eRefetch;