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[lldb] Return *const* UnwindPlan pointers from FuncUnwinders #133247

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Apr 2, 2025
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[lldb] Return *const* UnwindPlan pointers from FuncUnwinders #133247

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78 changes: 41 additions & 37 deletions lldb/include/lldb/Symbol/FuncUnwinders.h
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Original file line number Diff line number Diff line change
Expand Up @@ -36,18 +36,19 @@ class FuncUnwinders {

~FuncUnwinders();

lldb::UnwindPlanSP GetUnwindPlanAtCallSite(Target &target, Thread &thread);
std::shared_ptr<const UnwindPlan> GetUnwindPlanAtCallSite(Target &target,
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Can we change the UnwindPlanSP typedef? Do we ever need a non-const UnwindPlan shared pointer?

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Currently we need them, because the unwind plans are (sometimes) stored in a shared pointer while they are being constructed. That could be avoided because we don't really need the shared ownership at that point (they could be a unique_ptr or a value). However, I'm not particularly thrilled with the idea of repurposing UnwindPlanSP for this, as I think that would be surprising -- there's nothing in that name that indicates this is a const pointer, and I think it's important to see that.

One idea I have had that could solve this (but have never found the time to propose) is to replace the individual FoobarSP typedefs with a SP = std::shared_ptr<T> template alias. That would let us write SP<const Foobar> in exactly the places which need it; and it might also help with the hypothetical migration to the llvm naming convention (frees up FoobarSP as a member name)

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Makes sense.

One idea I have had that could solve this (but have never found the time to propose) is to replace the individual FoobarSP typedefs with a SP = std::shared_ptr template alias. That would let us write SP in exactly the places which need it; and it might also help with the hypothetical migration to the llvm naming convention (frees up FoobarSP as a member name)

Yeah, I remember you suggesting that in https://reviews.llvm.org/D133906. At the time I played around with a regex/python script to replace the existing FoobarSPs and it somehow was a lot harder to get right than I expected.

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Heh, that seems like quite a long time ago. Well.. I guess I'm at least consistent :)

I didn't realize you were actually experimenting with that approach. I'm going to take this to mean that such an idea has a non-zero chance of being accepted :) (ofc, there should be an rfc for that, and ideally some semi-automated method/tool to do the conversion)

Thread &thread);

lldb::UnwindPlanSP GetUnwindPlanAtNonCallSite(Target &target,
lldb_private::Thread &thread);
std::shared_ptr<const UnwindPlan>
GetUnwindPlanAtNonCallSite(Target &target, lldb_private::Thread &thread);

lldb::UnwindPlanSP GetUnwindPlanFastUnwind(Target &target,
lldb_private::Thread &thread);
std::shared_ptr<const UnwindPlan>
GetUnwindPlanFastUnwind(Target &target, lldb_private::Thread &thread);

lldb::UnwindPlanSP
std::shared_ptr<const UnwindPlan>
GetUnwindPlanArchitectureDefault(lldb_private::Thread &thread);

lldb::UnwindPlanSP
std::shared_ptr<const UnwindPlan>
GetUnwindPlanArchitectureDefaultAtFunctionEntry(lldb_private::Thread &thread);

Address &GetFirstNonPrologueInsn(Target &target);
Expand Down Expand Up @@ -77,32 +78,34 @@ class FuncUnwinders {
// used. Instead, clients should ask for the *behavior* they are looking for,
// using one of the above UnwindPlan retrieval methods.

lldb::UnwindPlanSP GetAssemblyUnwindPlan(Target &target, Thread &thread);
std::shared_ptr<const UnwindPlan> GetAssemblyUnwindPlan(Target &target,
Thread &thread);

lldb::UnwindPlanSP GetObjectFileUnwindPlan(Target &target);
std::shared_ptr<const UnwindPlan> GetObjectFileUnwindPlan(Target &target);

lldb::UnwindPlanSP GetObjectFileAugmentedUnwindPlan(Target &target,
Thread &thread);
std::shared_ptr<const UnwindPlan>
GetObjectFileAugmentedUnwindPlan(Target &target, Thread &thread);

lldb::UnwindPlanSP GetEHFrameUnwindPlan(Target &target);
std::shared_ptr<const UnwindPlan> GetEHFrameUnwindPlan(Target &target);

lldb::UnwindPlanSP GetEHFrameAugmentedUnwindPlan(Target &target,
Thread &thread);
std::shared_ptr<const UnwindPlan>
GetEHFrameAugmentedUnwindPlan(Target &target, Thread &thread);

lldb::UnwindPlanSP GetDebugFrameUnwindPlan(Target &target);
std::shared_ptr<const UnwindPlan> GetDebugFrameUnwindPlan(Target &target);

lldb::UnwindPlanSP GetDebugFrameAugmentedUnwindPlan(Target &target,
Thread &thread);
std::shared_ptr<const UnwindPlan>
GetDebugFrameAugmentedUnwindPlan(Target &target, Thread &thread);

lldb::UnwindPlanSP GetCompactUnwindUnwindPlan(Target &target);
std::shared_ptr<const UnwindPlan> GetCompactUnwindUnwindPlan(Target &target);

lldb::UnwindPlanSP GetArmUnwindUnwindPlan(Target &target);
std::shared_ptr<const UnwindPlan> GetArmUnwindUnwindPlan(Target &target);

lldb::UnwindPlanSP GetSymbolFileUnwindPlan(Thread &thread);
std::shared_ptr<const UnwindPlan> GetSymbolFileUnwindPlan(Thread &thread);

lldb::UnwindPlanSP GetArchDefaultUnwindPlan(Thread &thread);
std::shared_ptr<const UnwindPlan> GetArchDefaultUnwindPlan(Thread &thread);

lldb::UnwindPlanSP GetArchDefaultAtFuncEntryUnwindPlan(Thread &thread);
std::shared_ptr<const UnwindPlan>
GetArchDefaultAtFuncEntryUnwindPlan(Thread &thread);

private:
lldb::UnwindAssemblySP GetUnwindAssemblyProfiler(Target &target);
Expand All @@ -113,7 +116,8 @@ class FuncUnwinders {
// unwind rule for the pc, and LazyBoolCalculate if it was unable to
// determine this for some reason.
lldb_private::LazyBool CompareUnwindPlansForIdenticalInitialPCLocation(
Thread &thread, const lldb::UnwindPlanSP &a, const lldb::UnwindPlanSP &b);
Thread &thread, const std::shared_ptr<const UnwindPlan> &a,
const std::shared_ptr<const UnwindPlan> &b);

UnwindTable &m_unwind_table;

Expand All @@ -129,22 +133,22 @@ class FuncUnwinders {

std::recursive_mutex m_mutex;

lldb::UnwindPlanSP m_unwind_plan_assembly_sp;
lldb::UnwindPlanSP m_unwind_plan_object_file_sp;
lldb::UnwindPlanSP m_unwind_plan_eh_frame_sp;
lldb::UnwindPlanSP m_unwind_plan_debug_frame_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_assembly_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_object_file_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_eh_frame_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_debug_frame_sp;

// augmented by assembly inspection so it's valid everywhere
lldb::UnwindPlanSP m_unwind_plan_object_file_augmented_sp;
lldb::UnwindPlanSP m_unwind_plan_eh_frame_augmented_sp;
lldb::UnwindPlanSP m_unwind_plan_debug_frame_augmented_sp;

std::vector<lldb::UnwindPlanSP> m_unwind_plan_compact_unwind;
lldb::UnwindPlanSP m_unwind_plan_arm_unwind_sp;
lldb::UnwindPlanSP m_unwind_plan_symbol_file_sp;
lldb::UnwindPlanSP m_unwind_plan_fast_sp;
lldb::UnwindPlanSP m_unwind_plan_arch_default_sp;
lldb::UnwindPlanSP m_unwind_plan_arch_default_at_func_entry_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_object_file_augmented_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_eh_frame_augmented_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_debug_frame_augmented_sp;

std::vector<std::shared_ptr<const UnwindPlan>> m_unwind_plan_compact_unwind;
std::shared_ptr<const UnwindPlan> m_unwind_plan_arm_unwind_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_symbol_file_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_fast_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_arch_default_sp;
std::shared_ptr<const UnwindPlan> m_unwind_plan_arch_default_at_func_entry_sp;

// Fetching the UnwindPlans can be expensive - if we've already attempted to
// get one & failed, don't try again.
Expand Down
4 changes: 2 additions & 2 deletions lldb/include/lldb/Symbol/UnwindPlan.h
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Original file line number Diff line number Diff line change
Expand Up @@ -464,7 +464,7 @@ class UnwindPlan {
m_return_addr_register = regnum;
}

uint32_t GetReturnAddressRegister() { return m_return_addr_register; }
uint32_t GetReturnAddressRegister() const { return m_return_addr_register; }

uint32_t GetInitialCFARegister() const {
if (m_row_list.empty())
Expand All @@ -479,7 +479,7 @@ class UnwindPlan {
m_plan_valid_ranges = std::move(ranges);
}

bool PlanValidAtAddress(Address addr);
bool PlanValidAtAddress(Address addr) const;

bool IsValidRowIndex(uint32_t idx) const;

Expand Down
16 changes: 9 additions & 7 deletions lldb/include/lldb/Target/RegisterContextUnwind.h
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Expand Up @@ -127,7 +127,8 @@ class RegisterContextUnwind : public lldb_private::RegisterContext {

/// Check if the given unwind plan indicates a signal trap handler, and
/// update frame type and symbol context if so.
void PropagateTrapHandlerFlagFromUnwindPlan(lldb::UnwindPlanSP unwind_plan);
void PropagateTrapHandlerFlagFromUnwindPlan(
std::shared_ptr<const UnwindPlan> unwind_plan);

// Provide a location for where THIS function saved the CALLER's register
// value
Expand Down Expand Up @@ -194,16 +195,17 @@ class RegisterContextUnwind : public lldb_private::RegisterContext {
const UnwindPlan::Row::FAValue &fa,
lldb::addr_t &address);

lldb::UnwindPlanSP GetFastUnwindPlanForFrame();
std::shared_ptr<const UnwindPlan> GetFastUnwindPlanForFrame();

lldb::UnwindPlanSP GetFullUnwindPlanForFrame();
std::shared_ptr<const UnwindPlan> GetFullUnwindPlanForFrame();

void UnwindLogMsg(const char *fmt, ...) __attribute__((format(printf, 2, 3)));

void UnwindLogMsgVerbose(const char *fmt, ...)
__attribute__((format(printf, 2, 3)));

bool IsUnwindPlanValidForCurrentPC(lldb::UnwindPlanSP unwind_plan_sp);
bool IsUnwindPlanValidForCurrentPC(
std::shared_ptr<const UnwindPlan> unwind_plan_sp);

lldb::addr_t GetReturnAddressHint(int32_t plan_offset);

Expand All @@ -215,9 +217,9 @@ class RegisterContextUnwind : public lldb_private::RegisterContext {
// i.e. where THIS frame saved them
///

lldb::UnwindPlanSP m_fast_unwind_plan_sp; // may be NULL
lldb::UnwindPlanSP m_full_unwind_plan_sp;
lldb::UnwindPlanSP m_fallback_unwind_plan_sp; // may be NULL
std::shared_ptr<const UnwindPlan> m_fast_unwind_plan_sp; // may be NULL
std::shared_ptr<const UnwindPlan> m_full_unwind_plan_sp;
std::shared_ptr<const UnwindPlan> m_fallback_unwind_plan_sp; // may be NULL

bool m_all_registers_available; // Can we retrieve all regs or just
// nonvolatile regs?
Expand Down
106 changes: 49 additions & 57 deletions lldb/source/Commands/CommandObjectTarget.cpp
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Expand Up @@ -3641,85 +3641,78 @@ class CommandObjectTargetModulesShowUnwind : public CommandObjectParsed {

result.GetOutputStream().Printf("\n");

UnwindPlanSP non_callsite_unwind_plan =
func_unwinders_sp->GetUnwindPlanAtNonCallSite(*target, *thread);
if (non_callsite_unwind_plan) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetUnwindPlanAtNonCallSite(*target, *thread)) {
result.GetOutputStream().Printf(
"Asynchronous (not restricted to call-sites) UnwindPlan is '%s'\n",
non_callsite_unwind_plan->GetSourceName().AsCString());
plan_sp->GetSourceName().AsCString());
}
UnwindPlanSP callsite_unwind_plan =
func_unwinders_sp->GetUnwindPlanAtCallSite(*target, *thread);
if (callsite_unwind_plan) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetUnwindPlanAtCallSite(*target, *thread)) {
result.GetOutputStream().Printf(
"Synchronous (restricted to call-sites) UnwindPlan is '%s'\n",
callsite_unwind_plan->GetSourceName().AsCString());
plan_sp->GetSourceName().AsCString());
}
UnwindPlanSP fast_unwind_plan =
func_unwinders_sp->GetUnwindPlanFastUnwind(*target, *thread);
if (fast_unwind_plan) {
result.GetOutputStream().Printf(
"Fast UnwindPlan is '%s'\n",
fast_unwind_plan->GetSourceName().AsCString());
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetUnwindPlanFastUnwind(*target, *thread)) {
result.GetOutputStream().Printf("Fast UnwindPlan is '%s'\n",
plan_sp->GetSourceName().AsCString());
}

result.GetOutputStream().Printf("\n");

UnwindPlanSP assembly_sp =
func_unwinders_sp->GetAssemblyUnwindPlan(*target, *thread);
if (assembly_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetAssemblyUnwindPlan(*target, *thread)) {
result.GetOutputStream().Printf(
"Assembly language inspection UnwindPlan:\n");
assembly_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP of_unwind_sp =
func_unwinders_sp->GetObjectFileUnwindPlan(*target);
if (of_unwind_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetObjectFileUnwindPlan(*target)) {
result.GetOutputStream().Printf("object file UnwindPlan:\n");
of_unwind_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP of_unwind_augmented_sp =
func_unwinders_sp->GetObjectFileAugmentedUnwindPlan(*target, *thread);
if (of_unwind_augmented_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetObjectFileAugmentedUnwindPlan(*target,
*thread)) {
result.GetOutputStream().Printf("object file augmented UnwindPlan:\n");
of_unwind_augmented_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP ehframe_sp =
func_unwinders_sp->GetEHFrameUnwindPlan(*target);
if (ehframe_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetEHFrameUnwindPlan(*target)) {
result.GetOutputStream().Printf("eh_frame UnwindPlan:\n");
ehframe_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP ehframe_augmented_sp =
func_unwinders_sp->GetEHFrameAugmentedUnwindPlan(*target, *thread);
if (ehframe_augmented_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetEHFrameAugmentedUnwindPlan(*target,
*thread)) {
result.GetOutputStream().Printf("eh_frame augmented UnwindPlan:\n");
ehframe_augmented_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

if (UnwindPlanSP plan_sp =
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetDebugFrameUnwindPlan(*target)) {
result.GetOutputStream().Printf("debug_frame UnwindPlan:\n");
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

if (UnwindPlanSP plan_sp =
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetDebugFrameAugmentedUnwindPlan(*target,
*thread)) {
result.GetOutputStream().Printf("debug_frame augmented UnwindPlan:\n");
Expand All @@ -3728,36 +3721,35 @@ class CommandObjectTargetModulesShowUnwind : public CommandObjectParsed {
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP arm_unwind_sp =
func_unwinders_sp->GetArmUnwindUnwindPlan(*target);
if (arm_unwind_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetArmUnwindUnwindPlan(*target)) {
result.GetOutputStream().Printf("ARM.exidx unwind UnwindPlan:\n");
arm_unwind_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

if (UnwindPlanSP symfile_plan_sp =
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetSymbolFileUnwindPlan(*thread)) {
result.GetOutputStream().Printf("Symbol file UnwindPlan:\n");
symfile_plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

UnwindPlanSP compact_unwind_sp =
func_unwinders_sp->GetCompactUnwindUnwindPlan(*target);
if (compact_unwind_sp) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetCompactUnwindUnwindPlan(*target)) {
result.GetOutputStream().Printf("Compact unwind UnwindPlan:\n");
compact_unwind_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

if (fast_unwind_plan) {
if (std::shared_ptr<const UnwindPlan> plan_sp =
func_unwinders_sp->GetUnwindPlanFastUnwind(*target, *thread)) {
result.GetOutputStream().Printf("Fast UnwindPlan:\n");
fast_unwind_plan->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
plan_sp->Dump(result.GetOutputStream(), thread.get(),
LLDB_INVALID_ADDRESS);
result.GetOutputStream().Printf("\n");
}

Expand Down
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