CPPLanguageRuntime::LibCppStdFunctionCallableInfo
CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
lldb::ValueObjectSP &valobj_sp) {
LibCppStdFunctionCallableInfo optional_info;
if (!valobj_sp)
return optional_info;
// Member __f_ has type __base*, the contents of which will hold:
// 1) a vtable entry which may hold type information needed to discover the
// lambda being called
// 2) possibly hold a pointer to the callable object
// e.g.
//
// (lldb) frame var -R f_display
// (std::__1::function<void (int)>) f_display = {
// __buf_ = {
// …
// }
// __f_ = 0x00007ffeefbffa00
// }
// (lldb) memory read -fA 0x00007ffeefbffa00
// 0x7ffeefbffa00: ... `vtable for std::__1::__function::__func<void (*) ...
// 0x7ffeefbffa08: ... `print_num(int) at std_function_cppreference_exam ...
//
// We will be handling five cases below, std::function is wrapping:
//
// 1) a lambda we know at compile time. We will obtain the name of the lambda
// from the first template pameter from __func's vtable. We will look up
// the lambda's operator()() and obtain the line table entry.
// 2) a lambda we know at runtime. A pointer to the lambdas __invoke method
// will be stored after the vtable. We will obtain the lambdas name from
// this entry and lookup operator()() and obtain the line table entry.
// 3) a callable object via operator()(). We will obtain the name of the
// object from the first template parameter from __func's vtable. We will
// look up the objectc operator()() and obtain the line table entry.
// 4) a member function. A pointer to the function will stored after the
// we will obtain the name from this pointer.
// 5) a free function. A pointer to the function will stored after the vtable
// we will obtain the name from this pointer.
ValueObjectSP member__f_(
valobj_sp->GetChildMemberWithName(ConstString("__f_"), true));
if (member__f_) {
ValueObjectSP sub_member__f_(
member__f_->GetChildMemberWithName(ConstString("__f_"), true));
if (sub_member__f_)
member__f_ = sub_member__f_;
}
lldb::addr_t member__f_pointer_value = member__f_->GetValueAsUnsigned(0);
optional_info.member__f_pointer_value = member__f_pointer_value;
ExecutionContext exe_ctx(valobj_sp->GetExecutionContextRef());
Process *process = exe_ctx.GetProcessPtr();
if (process == nullptr)
return optional_info;
uint32_t address_size = process->GetAddressByteSize();
Status status;
// First item pointed to by __f_ should be the pointer to the vtable for
// a __base object.
lldb::addr_t vtable_address =
process->ReadPointerFromMemory(member__f_pointer_value, status);
if (status.Fail())
return optional_info;
lldb::addr_t address_after_vtable = member__f_pointer_value + address_size;
// As commened above we may not have a function pointer but if we do we will
// need it.
lldb::addr_t possible_function_address =
process->ReadPointerFromMemory(address_after_vtable, status);
if (status.Fail())
return optional_info;
Target &target = process->GetTarget();
if (target.GetSectionLoadList().IsEmpty())
return optional_info;
Address vtable_addr_resolved;
SymbolContext sc;
Symbol *symbol;
if (!target.GetSectionLoadList().ResolveLoadAddress(vtable_address,
vtable_addr_resolved))
return optional_info;
target.GetImages().ResolveSymbolContextForAddress(
vtable_addr_resolved, eSymbolContextEverything, sc);
symbol = sc.symbol;
if (symbol == nullptr)
return optional_info;
llvm::StringRef vtable_name(symbol->GetName().GetCString());
bool found_expected_start_string =
vtable_name.startswith("vtable for std::__1::__function::__func<");
if (!found_expected_start_string)
return optional_info;
// Given case 1 or 3 we have a vtable name, we are want to extract the first
// template parameter
//
// ... __func<main::$_0, std::__1::allocator<main::$_0> ...
// ^^^^^^^^^
//
// We do this by find the first < and , and extracting in between.
//
// This covers the case of the lambda known at compile time.
size_t first_open_angle_bracket = vtable_name.find('<') + 1;
size_t first_comma = vtable_name.find(',');
llvm::StringRef first_template_parameter =
vtable_name.slice(first_open_angle_bracket, first_comma);
Address function_address_resolved;
// Setup for cases 2, 4 and 5 we have a pointer to a function after the
// vtable. We will use a process of elimination to drop through each case
// and obtain the data we need.
if (target.GetSectionLoadList().ResolveLoadAddress(
possible_function_address, function_address_resolved)) {
target.GetImages().ResolveSymbolContextForAddress(
function_address_resolved, eSymbolContextEverything, sc);
symbol = sc.symbol;
}
auto get_name = [&first_template_parameter, &symbol]() {
// Given case 1:
//
// main::$_0
//
// we want to append ::operator()()
if (first_template_parameter.contains("$_"))
return llvm::Regex::escape(first_template_parameter.str()) +
R"(::operator\(\)\(.*\))";
if (symbol != NULL &&
symbol->GetName().GetStringRef().contains("__invoke")) {
llvm::StringRef symbol_name = symbol->GetName().GetStringRef();
size_t pos2 = symbol_name.find_last_of(':');
// Given case 2:
//
// main::$_1::__invoke(...)
//
// We want to slice off __invoke(...) and append operator()()
std::string lambda_operator =
llvm::Regex::escape(symbol_name.slice(0, pos2 + 1).str()) +
R"(operator\(\)\(.*\))";
return lambda_operator;
}
// Case 3
return first_template_parameter.str() + R"(::operator\(\)\(.*\))";
;
};
std::string func_to_match = get_name();
SymbolContextList scl;
target.GetImages().FindFunctions(RegularExpression{func_to_match}, true, true,
true, scl);
// Case 1,2 or 3
if (scl.GetSize() >= 1) {
SymbolContext sc2 = scl[0];
AddressRange range;
sc2.GetAddressRange(eSymbolContextEverything, 0, false, range);
Address address = range.GetBaseAddress();
Address addr;
if (target.ResolveLoadAddress(address.GetCallableLoadAddress(&target),
addr)) {
LineEntry line_entry;
addr.CalculateSymbolContextLineEntry(line_entry);
if (first_template_parameter.contains("$_") ||
(symbol != nullptr &&
symbol->GetName().GetStringRef().contains("__invoke"))) {
// Case 1 and 2
optional_info.callable_case = LibCppStdFunctionCallableCase::Lambda;
} else {
// Case 3
optional_info.callable_case =
LibCppStdFunctionCallableCase::CallableObject;
}
optional_info.callable_symbol = *symbol;
optional_info.callable_line_entry = line_entry;
optional_info.callable_address = addr;
return optional_info;
}
