llvm-project/lldb/source/Core/ValueObjectVariable.cpp

//===-- ValueObjectVariable.cpp ---------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//


#include "lldb/Core/ValueObjectVariable.h"

// C Includes
// C++ Includes
// Other libraries and framework includes
// Project includes
#include "lldb/Core/Module.h"
#include "lldb/Core/RegisterValue.h"
#include "lldb/Core/ValueObjectList.h"
#include "lldb/Core/Value.h"

#include "lldb/Symbol/Function.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/SymbolContext.h"
#include "lldb/Symbol/SymbolContextScope.h"
#include "lldb/Symbol/Type.h"
#include "lldb/Symbol/Variable.h"

#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Thread.h"


using namespace lldb_private;

lldb::ValueObjectSP
ValueObjectVariable::Create (ExecutionContextScope *exe_scope, const lldb::VariableSP &var_sp)
{
    return (new ValueObjectVariable (exe_scope, var_sp))->GetSP();
}

ValueObjectVariable::ValueObjectVariable (ExecutionContextScope *exe_scope, const lldb::VariableSP &var_sp) :
    ValueObject(exe_scope),
    m_variable_sp(var_sp)
{
    // Do not attempt to construct one of these objects with no variable!
    assert (m_variable_sp.get() != NULL);
    m_name = var_sp->GetName();
}

ValueObjectVariable::~ValueObjectVariable()
{
}

CompilerType
ValueObjectVariable::GetCompilerTypeImpl ()
{
    Type *var_type = m_variable_sp->GetType();
    if (var_type)
        return var_type->GetForwardCompilerType ();
    return CompilerType();
}

ConstString
ValueObjectVariable::GetTypeName()
{
    Type * var_type = m_variable_sp->GetType();
    if (var_type)
        return var_type->GetName();
    return ConstString();
}

ConstString
ValueObjectVariable::GetDisplayTypeName()
{
    Type * var_type = m_variable_sp->GetType();
    if (var_type)
        return var_type->GetForwardCompilerType ().GetDisplayTypeName();
    return ConstString();
}

ConstString
ValueObjectVariable::GetQualifiedTypeName()
{
    Type * var_type = m_variable_sp->GetType();
    if (var_type)
        return var_type->GetQualifiedName();
    return ConstString();
}

size_t
ValueObjectVariable::CalculateNumChildren(uint32_t max)
{    
    CompilerType type(GetCompilerType());
    
    if (!type.IsValid())
        return 0;
    
    const bool omit_empty_base_classes = true;
    auto child_count = type.GetNumChildren(omit_empty_base_classes);
    return child_count <= max ? child_count : max;
}

uint64_t
ValueObjectVariable::GetByteSize()
{
    ExecutionContext exe_ctx(GetExecutionContextRef());
    
    CompilerType type(GetCompilerType());
    
    if (!type.IsValid())
        return 0;
    
    return type.GetByteSize(exe_ctx.GetBestExecutionContextScope());
}

lldb::ValueType
ValueObjectVariable::GetValueType() const
{
    if (m_variable_sp)
        return m_variable_sp->GetScope();
    return lldb::eValueTypeInvalid;
}

bool
ValueObjectVariable::UpdateValue ()
{
    SetValueIsValid (false);
    m_error.Clear();

    Variable *variable = m_variable_sp.get();
    DWARFExpression &expr = variable->LocationExpression();
    
    if (variable->GetLocationIsConstantValueData())
    {
        // expr doesn't contain DWARF bytes, it contains the constant variable
        // value bytes themselves...
        if (expr.GetExpressionData(m_data))
            m_value.SetContext(Value::eContextTypeVariable, variable);
        else
            m_error.SetErrorString ("empty constant data");
        // constant bytes can't be edited - sorry
        m_resolved_value.SetContext(Value::eContextTypeInvalid, NULL);
    }
    else
    {
        lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
        ExecutionContext exe_ctx (GetExecutionContextRef());
        
        Target *target = exe_ctx.GetTargetPtr();
        if (target)
        {
            m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
            m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
        }

        if (expr.IsLocationList())
        {
            SymbolContext sc;
            variable->CalculateSymbolContext (&sc);
            if (sc.function)
                loclist_base_load_addr = sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress (target);
        }
        Value old_value(m_value);
        if (expr.Evaluate (&exe_ctx,
                           nullptr,
                           nullptr,
                           nullptr,
                           loclist_base_load_addr,
                           nullptr,
                           nullptr,
                           m_value,
                           &m_error))
        {
            m_resolved_value = m_value;
            m_value.SetContext(Value::eContextTypeVariable, variable);
            
            CompilerType compiler_type = GetCompilerType();
            if (compiler_type.IsValid())
                m_value.SetCompilerType(compiler_type);

            Value::ValueType value_type = m_value.GetValueType();

            Process *process = exe_ctx.GetProcessPtr();
            const bool process_is_alive = process && process->IsAlive();
            const uint32_t type_info = compiler_type.GetTypeInfo();
            const bool is_pointer_or_ref = (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;

            switch (value_type)
            {
                case Value::eValueTypeFileAddress:
                    // If this type is a pointer, then its children will be considered load addresses
                    // if the pointer or reference is dereferenced, but only if the process is alive.
                    //
                    // There could be global variables like in the following code:
                    // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
                    // Foo g_foo1;
                    // Foo g_foo2;
                    // LinkedListNode g_second_node = { &g_foo2, NULL };
                    // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
                    //
                    // When we aren't running, we should be able to look at these variables using
                    // the "target variable" command. Children of the "g_first_node" always will
                    // be of the same address type as the parent. But children of the "next" member of
                    // LinkedListNode will become load addresses if we have a live process, or remain
                    // what a file address if it what a file address.
                    if (process_is_alive && is_pointer_or_ref)
                        SetAddressTypeOfChildren(eAddressTypeLoad);
                    else
                        SetAddressTypeOfChildren(eAddressTypeFile);
                    break;
                case Value::eValueTypeHostAddress:
                    // Same as above for load addresses, except children of pointer or refs are always
                    // load addresses. Host addresses are used to store freeze dried variables. If this
                    // type is a struct, the entire struct contents will be copied into the heap of the
                    // LLDB process, but we do not currrently follow any pointers.
                    if (is_pointer_or_ref)
                        SetAddressTypeOfChildren(eAddressTypeLoad);
                    else
                        SetAddressTypeOfChildren(eAddressTypeHost);
                    break;
                case Value::eValueTypeLoadAddress:
                case Value::eValueTypeScalar:
                case Value::eValueTypeVector:
                    SetAddressTypeOfChildren(eAddressTypeLoad);
                    break;
            }

            switch (value_type)
            {
            case Value::eValueTypeVector:
                    // fall through
            case Value::eValueTypeScalar:
                // The variable value is in the Scalar value inside the m_value.
                // We can point our m_data right to it.
                m_error = m_value.GetValueAsData (&exe_ctx, m_data, 0, GetModule().get());
                break;

            case Value::eValueTypeFileAddress:
            case Value::eValueTypeLoadAddress:
            case Value::eValueTypeHostAddress:
                // The DWARF expression result was an address in the inferior
                // process. If this variable is an aggregate type, we just need
                // the address as the main value as all child variable objects
                // will rely upon this location and add an offset and then read
                // their own values as needed. If this variable is a simple
                // type, we read all data for it into m_data.
                // Make sure this type has a value before we try and read it

                // If we have a file address, convert it to a load address if we can.
                if (value_type == Value::eValueTypeFileAddress && process_is_alive)
                {
                    lldb::addr_t file_addr = m_value.GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
                    if (file_addr != LLDB_INVALID_ADDRESS)
                    {
                        SymbolContext var_sc;
                        variable->CalculateSymbolContext(&var_sc);
                        if (var_sc.module_sp)
                        {
                            ObjectFile *objfile = var_sc.module_sp->GetObjectFile();
                            if (objfile)
                            {
                                Address so_addr(file_addr, objfile->GetSectionList());
                                lldb::addr_t load_addr = so_addr.GetLoadAddress (target);
                                if (load_addr != LLDB_INVALID_ADDRESS)
                                {
                                    m_value.SetValueType(Value::eValueTypeLoadAddress);
                                    m_value.GetScalar() = load_addr;
                                }
                            }
                        }
                    }
                }

                if (!CanProvideValue())
                {
                    // this value object represents an aggregate type whose
                    // children have values, but this object does not. So we
                    // say we are changed if our location has changed.
                    SetValueDidChange (value_type != old_value.GetValueType() || m_value.GetScalar() != old_value.GetScalar());
                }
                else
                {
                    // Copy the Value and set the context to use our Variable
                    // so it can extract read its value into m_data appropriately
                    Value value(m_value);
                    value.SetContext(Value::eContextTypeVariable, variable);
                    m_error = value.GetValueAsData(&exe_ctx, m_data, 0, GetModule().get());
                    
                    SetValueDidChange (value_type != old_value.GetValueType() || m_value.GetScalar() != old_value.GetScalar());
                }
                break;
            }

            SetValueIsValid (m_error.Success());
        }
        else
        {
            // could not find location, won't allow editing
            m_resolved_value.SetContext(Value::eContextTypeInvalid, NULL);
        }
    }
    return m_error.Success();
}



bool
ValueObjectVariable::IsInScope ()
{
    const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
    if (exe_ctx_ref.HasFrameRef())
    {
        ExecutionContext exe_ctx (exe_ctx_ref);
        StackFrame *frame = exe_ctx.GetFramePtr();
        if (frame)
        {
            return m_variable_sp->IsInScope (frame);
        }
        else
        {
            // This ValueObject had a frame at one time, but now we
            // can't locate it, so return false since we probably aren't
            // in scope.
            return false;
        }
    }
    // We have a variable that wasn't tied to a frame, which
    // means it is a global and is always in scope.
    return true;
         
}

lldb::ModuleSP
ValueObjectVariable::GetModule()
{
    if (m_variable_sp)
    {
        SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
        if (sc_scope)
        {
            return sc_scope->CalculateSymbolContextModule();
        }
    }
    return lldb::ModuleSP();
}

SymbolContextScope *
ValueObjectVariable::GetSymbolContextScope()
{
    if (m_variable_sp)
        return m_variable_sp->GetSymbolContextScope();
    return NULL;
}

bool
ValueObjectVariable::GetDeclaration (Declaration &decl)
{
    if (m_variable_sp)
    {
        decl = m_variable_sp->GetDeclaration();
        return true;
    }
    return false;
}

const char *
ValueObjectVariable::GetLocationAsCString ()
{
    if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo)
        return GetLocationAsCStringImpl(m_resolved_value,
                                        m_data);
    else
        return ValueObject::GetLocationAsCString();
}

bool
ValueObjectVariable::SetValueFromCString (const char *value_str, Error& error)
{
    if (!UpdateValueIfNeeded())
    {
        error.SetErrorString("unable to update value before writing");
        return false;
    }
    
    if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo)
    {
        RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
        ExecutionContext exe_ctx(GetExecutionContextRef());
        RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
        RegisterValue reg_value;
        if (!reg_info || !reg_ctx)
        {
            error.SetErrorString("unable to retrieve register info");
            return false;
        }
        error = reg_value.SetValueFromCString(reg_info, value_str);
        if (error.Fail())
            return false;
        if (reg_ctx->WriteRegister (reg_info, reg_value))
        {
            SetNeedsUpdate();
            return true;
        }
        else
        {
            error.SetErrorString("unable to write back to register");
            return false;
        }
    }
    else
        return ValueObject::SetValueFromCString(value_str, error);
}

bool
ValueObjectVariable::SetData (DataExtractor &data, Error &error)
{
    if (!UpdateValueIfNeeded())
    {
        error.SetErrorString("unable to update value before writing");
        return false;
    }
    
    if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo)
    {
        RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
        ExecutionContext exe_ctx(GetExecutionContextRef());
        RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
        RegisterValue reg_value;
        if (!reg_info || !reg_ctx)
        {
            error.SetErrorString("unable to retrieve register info");
            return false;
        }
        error = reg_value.SetValueFromData(reg_info, data, 0, true);
        if (error.Fail())
            return false;
        if (reg_ctx->WriteRegister (reg_info, reg_value))
        {
            SetNeedsUpdate();
            return true;
        }
        else
        {
            error.SetErrorString("unable to write back to register");
            return false;
        }
    }
    else
        return ValueObject::SetData(data, error);
}