Skip to content

[lldb] Make ValueObject::Dereference less aggressive #137311

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Apr 29, 2025
Merged

[lldb] Make ValueObject::Dereference less aggressive #137311

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
a295fdb
[lldb] Make ValueObject::Dereference less aggressive
labath Apr 25, 2025
22b7b79
Update lldb/source/ValueObject/ValueObject.cpp
labath Apr 28, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 11 additions & 9 deletions lldb/source/Target/StackFrame.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -709,21 +709,17 @@ ValueObjectSP StackFrame::LegacyGetValueForVariableExpressionPath(
// we have a synthetic dereference specified.
if (!valobj_sp->IsPointerType() && valobj_sp->HasSyntheticValue()) {
Status deref_error;
if (valobj_sp->GetCompilerType().IsReferenceType()) {
valobj_sp = valobj_sp->GetSyntheticValue()->Dereference(deref_error);
if (!valobj_sp || deref_error.Fail()) {
error = Status::FromErrorStringWithFormatv(
"Failed to dereference reference type: {0}", deref_error);
return ValueObjectSP();
}
if (ValueObjectSP synth_deref_sp =
valobj_sp->GetSyntheticValue()->Dereference(deref_error);
synth_deref_sp && deref_error.Success()) {
valobj_sp = std::move(synth_deref_sp);
}

valobj_sp = valobj_sp->Dereference(deref_error);
if (!valobj_sp || deref_error.Fail()) {
error = Status::FromErrorStringWithFormatv(
"Failed to dereference synthetic value: {0}", deref_error);
return ValueObjectSP();
}

// Some synthetic plug-ins fail to set the error in Dereference
if (!valobj_sp) {
error =
Expand Down Expand Up @@ -1129,6 +1125,12 @@ ValueObjectSP StackFrame::LegacyGetValueForVariableExpressionPath(
if (valobj_sp) {
if (deref) {
ValueObjectSP deref_valobj_sp(valobj_sp->Dereference(error));
if (!deref_valobj_sp && !no_synth_child) {
if (ValueObjectSP synth_obj_sp = valobj_sp->GetSyntheticValue()) {
error.Clear();
deref_valobj_sp = synth_obj_sp->Dereference(error);
}
}
valobj_sp = deref_valobj_sp;
} else if (address_of) {
ValueObjectSP address_of_valobj_sp(valobj_sp->AddressOf(error));
Expand Down
204 changes: 72 additions & 132 deletions lldb/source/ValueObject/ValueObject.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2202,6 +2202,45 @@ void ValueObject::GetExpressionPath(Stream &s,
}
}

// Return the alternate value (synthetic if the input object is non-synthetic
// and otherwise) this is permitted by the expression path options.
static ValueObjectSP GetAlternateValue(
ValueObject &valobj,
ValueObject::GetValueForExpressionPathOptions::SyntheticChildrenTraversal
synth_traversal) {
using SynthTraversal =
ValueObject::GetValueForExpressionPathOptions::SyntheticChildrenTraversal;

if (valobj.IsSynthetic()) {
if (synth_traversal == SynthTraversal::FromSynthetic ||
synth_traversal == SynthTraversal::Both)
return valobj.GetNonSyntheticValue();
} else {
if (synth_traversal == SynthTraversal::ToSynthetic ||
synth_traversal == SynthTraversal::Both)
return valobj.GetSyntheticValue();
}
return nullptr;
}

// Dereference the provided object or the alternate value, if permitted by the
// expression path options.
static ValueObjectSP DereferenceValueOrAlternate(
ValueObject &valobj,
ValueObject::GetValueForExpressionPathOptions::SyntheticChildrenTraversal
synth_traversal,
Status &error) {
error.Clear();
ValueObjectSP result = valobj.Dereference(error);
if (!result || error.Fail()) {
if (ValueObjectSP alt_obj = GetAlternateValue(valobj, synth_traversal)) {
error.Clear();
result = alt_obj->Dereference(error);
}
}
return result;
}

ValueObjectSP ValueObject::GetValueForExpressionPath(
llvm::StringRef expression, ExpressionPathScanEndReason *reason_to_stop,
ExpressionPathEndResultType *final_value_type,
Expand Down Expand Up @@ -2234,7 +2273,8 @@ ValueObjectSP ValueObject::GetValueForExpressionPath(
: dummy_final_task_on_target) ==
ValueObject::eExpressionPathAftermathDereference) {
Status error;
ValueObjectSP final_value = ret_val->Dereference(error);
ValueObjectSP final_value = DereferenceValueOrAlternate(
*ret_val, options.m_synthetic_children_traversal, error);
if (error.Fail() || !final_value.get()) {
if (reason_to_stop)
*reason_to_stop =
Expand Down Expand Up @@ -2348,144 +2388,45 @@ ValueObjectSP ValueObject::GetValueForExpressionPath_Impl(
temp_expression = temp_expression.drop_front(); // skip . or >

size_t next_sep_pos = temp_expression.find_first_of("-.[", 1);
if (next_sep_pos == llvm::StringRef::npos) // if no other separator just
// expand this last layer
{
if (next_sep_pos == llvm::StringRef::npos) {
// if no other separator just expand this last layer
llvm::StringRef child_name = temp_expression;
ValueObjectSP child_valobj_sp =
root->GetChildMemberWithName(child_name);

if (child_valobj_sp.get()) // we know we are done, so just return
{
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonEndOfString;
*final_result = ValueObject::eExpressionPathEndResultTypePlain;
return child_valobj_sp;
} else {
switch (options.m_synthetic_children_traversal) {
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
None:
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
FromSynthetic:
if (root->IsSynthetic()) {
child_valobj_sp = root->GetNonSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
ToSynthetic:
if (!root->IsSynthetic()) {
child_valobj_sp = root->GetSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
Both:
if (root->IsSynthetic()) {
child_valobj_sp = root->GetNonSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
} else {
child_valobj_sp = root->GetSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
}
if (!child_valobj_sp) {
if (ValueObjectSP altroot = GetAlternateValue(
*root, options.m_synthetic_children_traversal))
child_valobj_sp = altroot->GetChildMemberWithName(child_name);
}

// if we are here and options.m_no_synthetic_children is true,
// child_valobj_sp is going to be a NULL SP, so we hit the "else"
// branch, and return an error
if (child_valobj_sp.get()) // if it worked, just return
{
if (child_valobj_sp) {
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonEndOfString;
*final_result = ValueObject::eExpressionPathEndResultTypePlain;
return child_valobj_sp;
} else {
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonNoSuchChild;
*final_result = ValueObject::eExpressionPathEndResultTypeInvalid;
return nullptr;
}
} else // other layers do expand
{
llvm::StringRef next_separator = temp_expression.substr(next_sep_pos);
llvm::StringRef child_name = temp_expression.slice(0, next_sep_pos);
*reason_to_stop = ValueObject::eExpressionPathScanEndReasonNoSuchChild;
*final_result = ValueObject::eExpressionPathEndResultTypeInvalid;
return nullptr;
}

ValueObjectSP child_valobj_sp =
root->GetChildMemberWithName(child_name);
if (child_valobj_sp.get()) // store the new root and move on
{
root = child_valobj_sp;
remainder = next_separator;
*final_result = ValueObject::eExpressionPathEndResultTypePlain;
continue;
} else {
switch (options.m_synthetic_children_traversal) {
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
None:
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
FromSynthetic:
if (root->IsSynthetic()) {
child_valobj_sp = root->GetNonSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
ToSynthetic:
if (!root->IsSynthetic()) {
child_valobj_sp = root->GetSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
case GetValueForExpressionPathOptions::SyntheticChildrenTraversal::
Both:
if (root->IsSynthetic()) {
child_valobj_sp = root->GetNonSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
} else {
child_valobj_sp = root->GetSyntheticValue();
if (child_valobj_sp.get())
child_valobj_sp =
child_valobj_sp->GetChildMemberWithName(child_name);
}
break;
}
}
llvm::StringRef next_separator = temp_expression.substr(next_sep_pos);
llvm::StringRef child_name = temp_expression.slice(0, next_sep_pos);

// if we are here and options.m_no_synthetic_children is true,
// child_valobj_sp is going to be a NULL SP, so we hit the "else"
// branch, and return an error
if (child_valobj_sp.get()) // if it worked, move on
{
root = child_valobj_sp;
remainder = next_separator;
*final_result = ValueObject::eExpressionPathEndResultTypePlain;
continue;
} else {
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonNoSuchChild;
*final_result = ValueObject::eExpressionPathEndResultTypeInvalid;
return nullptr;
}
ValueObjectSP child_valobj_sp = root->GetChildMemberWithName(child_name);
if (!child_valobj_sp) {
if (ValueObjectSP altroot = GetAlternateValue(
*root, options.m_synthetic_children_traversal))
child_valobj_sp = altroot->GetChildMemberWithName(child_name);
}
break;
if (child_valobj_sp) {
root = child_valobj_sp;
remainder = next_separator;
*final_result = ValueObject::eExpressionPathEndResultTypePlain;
continue;
}
*reason_to_stop = ValueObject::eExpressionPathScanEndReasonNoSuchChild;
*final_result = ValueObject::eExpressionPathEndResultTypeInvalid;
return nullptr;
}
case '[': {
if (!root_compiler_type_info.Test(eTypeIsArray) &&
Expand Down Expand Up @@ -2601,7 +2542,8 @@ ValueObjectSP ValueObject::GetValueForExpressionPath_Impl(
// a bitfield
pointee_compiler_type_info.Test(eTypeIsScalar)) {
Status error;
root = root->Dereference(error);
root = DereferenceValueOrAlternate(
*root, options.m_synthetic_children_traversal, error);
if (error.Fail() || !root) {
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonDereferencingFailed;
Expand Down Expand Up @@ -2746,7 +2688,8 @@ ValueObjectSP ValueObject::GetValueForExpressionPath_Impl(
ValueObject::eExpressionPathAftermathDereference &&
pointee_compiler_type_info.Test(eTypeIsScalar)) {
Status error;
root = root->Dereference(error);
root = DereferenceValueOrAlternate(
*root, options.m_synthetic_children_traversal, error);
if (error.Fail() || !root) {
*reason_to_stop =
ValueObject::eExpressionPathScanEndReasonDereferencingFailed;
Expand Down Expand Up @@ -2916,9 +2859,6 @@ ValueObjectSP ValueObject::Dereference(Status &error) {
}
}

} else if (HasSyntheticValue()) {
m_deref_valobj =
GetSyntheticValue()->GetChildMemberWithName("$$dereference$$").get();
} else if (IsSynthetic()) {
m_deref_valobj = GetChildMemberWithName("$$dereference$$").get();
}
Expand Down
Loading