source/Expression/ClangExpressionDeclMap.cpp

//===-- ClangExpressionDeclMap.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/Expression/ClangExpressionDeclMap.h"

// C Includes
// C++ Includes
// Other libraries and framework includes
// Project includes
#include "clang/AST/DeclarationName.h"
#include "lldb/lldb-private.h"
#include "lldb/Core/Address.h"
#include "lldb/Core/Error.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/Module.h"
#include "lldb/Expression/ClangASTSource.h"
#include "lldb/Expression/ClangPersistentVariables.h"
#include "lldb/Symbol/ClangASTContext.h"
#include "lldb/Symbol/CompileUnit.h"
#include "lldb/Symbol/Function.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/SymbolContext.h"
#include "lldb/Symbol/Type.h"
#include "lldb/Symbol/TypeList.h"
#include "lldb/Symbol/Variable.h"
#include "lldb/Symbol/VariableList.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/StackFrame.h"
#include "lldb/Target/Target.h"

using namespace lldb_private;
using namespace clang;

ClangExpressionDeclMap::ClangExpressionDeclMap(ExecutionContext *exe_ctx) :
    m_exe_ctx(exe_ctx),    m_struct_laid_out(false),
    m_materialized_location(0)
{
    if (exe_ctx && exe_ctx->frame)
        m_sym_ctx = new SymbolContext(exe_ctx->frame->GetSymbolContext(lldb::eSymbolContextEverything));
    else
        m_sym_ctx = NULL;
    
    if (exe_ctx && exe_ctx->process)
        m_persistent_vars = &exe_ctx->process->GetPersistentVariables();
}

ClangExpressionDeclMap::~ClangExpressionDeclMap()
{    
    for (uint64_t entity_index = 0, num_entities = m_found_entities.Size();
         entity_index < num_entities;
         ++entity_index)
    {
        ClangExpressionVariable &entity(m_found_entities.VariableAtIndex(entity_index));
        if (entity.m_parser_vars.get() &&
            entity.m_parser_vars->m_lldb_value)
            delete entity.m_parser_vars->m_lldb_value;
        
        entity.DisableParserVars();
    }
    
    for (uint64_t pvar_index = 0, num_pvars = m_persistent_vars->Size();
         pvar_index < num_pvars;
         ++pvar_index)
    {
        ClangExpressionVariable &pvar(m_persistent_vars->VariableAtIndex(pvar_index));
        pvar.DisableParserVars();
    }
    
    if (m_materialized_location)
    {
        m_exe_ctx->process->DeallocateMemory(m_materialized_location);
        m_materialized_location = 0;
    }
    
    if (m_sym_ctx)
        delete m_sym_ctx;
}

// Interface for IRForTarget

void
ClangExpressionDeclMap::GetPersistentResultName (std::string &name)
{
    m_persistent_vars->GetNextResultName(m_result_name);
    
    name = m_result_name;
}

bool 
ClangExpressionDeclMap::AddPersistentVariable (const clang::NamedDecl *decl, 
                                               const char *name, 
                                               TypeFromParser parser_type)
{
    clang::ASTContext *context(m_exe_ctx->target->GetScratchClangASTContext()->getASTContext());
    
    TypeFromUser user_type(ClangASTContext::CopyType(context, 
                                                     parser_type.GetASTContext(),
                                                     parser_type.GetOpaqueQualType()),
                            context);
    
    if (!m_persistent_vars->CreatePersistentVariable (name, user_type))
        return false;
    
    ClangExpressionVariable *var = m_persistent_vars->GetVariable(name);
    
    if (!var)
        return false;
    
    var->EnableParserVars();
    
    var->m_parser_vars->m_named_decl = decl;
    var->m_parser_vars->m_parser_type = parser_type;
    
    return true;
}

bool 
ClangExpressionDeclMap::AddValueToStruct (const clang::NamedDecl *decl,
                                          const char *name,
                                          llvm::Value *value,
                                          size_t size,
                                          off_t alignment)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    m_struct_laid_out = false;
    
    if (m_struct_members.GetVariable(decl))
        return true;
    
    ClangExpressionVariable *var = m_found_entities.GetVariable(decl);
    
    if (!var)
        var = m_persistent_vars->GetVariable(decl);
    
    if (!var)
        return false;
    
    if (log)
        log->Printf("Adding value for decl %p [%s - %s] to the structure",
                    decl,
                    name,
                    var->m_name.c_str());
    
    // We know entity->m_parser_vars is valid because we used a parser variable
    // to find it
    var->m_parser_vars->m_llvm_value = value;
    
    var->EnableJITVars();
    var->m_jit_vars->m_alignment = alignment;
    var->m_jit_vars->m_size = size;
    
    m_struct_members.AddVariable(*var);
    
    return true;
}

bool
ClangExpressionDeclMap::DoStructLayout ()
{
    if (m_struct_laid_out)
        return true;
    
    off_t cursor = 0;
    
    m_struct_alignment = 0;
    m_struct_size = 0;
    
    for (uint64_t member_index = 0, num_members = m_struct_members.Size();
         member_index < num_members;
         ++member_index)
    {
        ClangExpressionVariable &member(m_struct_members.VariableAtIndex(member_index));
        
        if (!member.m_jit_vars.get())
            return false;
        
        if (member_index == 0)
            m_struct_alignment = member.m_jit_vars->m_alignment;
        
        if (cursor % member.m_jit_vars->m_alignment)
            cursor += (member.m_jit_vars->m_alignment - (cursor % member.m_jit_vars->m_alignment));
        
        member.m_jit_vars->m_offset = cursor;
        cursor += member.m_jit_vars->m_size;
    }
    
    m_struct_size = cursor;
    
    m_struct_laid_out = true;
    return true;
}

bool ClangExpressionDeclMap::GetStructInfo (uint32_t &num_elements,
                                            size_t &size,
                                            off_t &alignment)
{
    if (!m_struct_laid_out)
        return false;
    
    num_elements = m_struct_members.Size();
    size = m_struct_size;
    alignment = m_struct_alignment;
    
    return true;
}

bool 
ClangExpressionDeclMap::GetStructElement (const clang::NamedDecl *&decl,
                                          llvm::Value *&value,
                                          off_t &offset,
                                          const char *&name,
                                          uint32_t index)
{
    if (!m_struct_laid_out)
        return false;
    
    if (index >= m_struct_members.Size())
        return false;
    
    ClangExpressionVariable &member(m_struct_members.VariableAtIndex(index));
    
    if (!member.m_parser_vars.get() ||
        !member.m_jit_vars.get())
        return false;
    
    decl = member.m_parser_vars->m_named_decl;
    value = member.m_parser_vars->m_llvm_value;
    offset = member.m_jit_vars->m_offset;
    name = member.m_name.c_str();
        
    return true;
}

bool
ClangExpressionDeclMap::GetFunctionInfo (const clang::NamedDecl *decl, 
                                         llvm::Value**& value, 
                                         uint64_t &ptr)
{
    ClangExpressionVariable *entity = m_found_entities.GetVariable(decl);

    if (!entity)
        return false;
    
    // We know m_parser_vars is valid since we searched for the variable by
    // its NamedDecl
    
    value = &entity->m_parser_vars->m_llvm_value;
    ptr = entity->m_parser_vars->m_lldb_value->GetScalar().ULongLong();
    
    return true;
}

bool
ClangExpressionDeclMap::GetFunctionAddress (const char *name,
                                            uint64_t &ptr)
{
    // Back out in all cases where we're not fully initialized
    if (!m_exe_ctx || !m_exe_ctx->frame || !m_sym_ctx)
        return false;

    ConstString name_cs(name);
    SymbolContextList sym_ctxs;
    
    m_sym_ctx->FindFunctionsByName(name_cs, false, sym_ctxs);
    
    if (!sym_ctxs.GetSize())
        return false;
    
    SymbolContext sym_ctx;
    sym_ctxs.GetContextAtIndex(0, sym_ctx);
    
    const Address *fun_address;
    
    if (sym_ctx.function)
        fun_address = &sym_ctx.function->GetAddressRange().GetBaseAddress();
    else if (sym_ctx.symbol)
        fun_address = &sym_ctx.symbol->GetAddressRangeRef().GetBaseAddress();
    else
        return false;
    
    ptr = fun_address->GetLoadAddress(m_exe_ctx->target);
    
    return true;
}

// Interface for CommandObjectExpression

bool 
ClangExpressionDeclMap::Materialize (ExecutionContext *exe_ctx, 
                                     lldb::addr_t &struct_address,
                                     Error &err)
{
    bool result = DoMaterialize(false, exe_ctx, NULL, err);
    
    if (result)
        struct_address = m_materialized_location;
    
    return result;
}

bool 
ClangExpressionDeclMap::GetObjectPointer(lldb::addr_t &object_ptr,
                                         ExecutionContext *exe_ctx,
                                         Error &err)
{
    if (!exe_ctx || !exe_ctx->frame || !exe_ctx->target || !exe_ctx->process)
    {
        err.SetErrorString("Couldn't load 'this' because the context is incomplete");
        return false;
    }
    
    if (!m_object_pointer_type.GetOpaqueQualType())
    {
        err.SetErrorString("Couldn't load 'this' because its type is unknown");
        return false;
    }
    
    Variable *object_ptr_var = FindVariableInScope(*exe_ctx->frame, "this", &m_object_pointer_type);
    
    if (!object_ptr_var)
    {
        err.SetErrorString("Couldn't find 'this' with appropriate type in scope");
        return false;
    }
    
    std::auto_ptr<lldb_private::Value> location_value(GetVariableValue(*exe_ctx,
                                                                       object_ptr_var,
                                                                       m_object_pointer_type.GetASTContext()));
    
    if (!location_value.get())
    {
        err.SetErrorString("Couldn't get the location for 'this'");
        return false;
    }
    
    if (location_value->GetValueType() == Value::eValueTypeLoadAddress)
    {
        lldb::addr_t value_addr = location_value->GetScalar().ULongLong();
        uint32_t address_byte_size = exe_ctx->target->GetArchitecture().GetAddressByteSize();
        lldb::ByteOrder address_byte_order = exe_ctx->process->GetByteOrder();
        
        if (ClangASTType::GetClangTypeBitWidth(m_object_pointer_type.GetASTContext(), m_object_pointer_type.GetOpaqueQualType()) != address_byte_size * 8)
        {
            err.SetErrorStringWithFormat("'this' is not of an expected pointer size");
            return false;
        }
        
        DataBufferHeap data;
        data.SetByteSize(address_byte_size);
        Error read_error;
        
        if (exe_ctx->process->ReadMemory (value_addr, data.GetBytes(), address_byte_size, read_error) != address_byte_size)
        {
            err.SetErrorStringWithFormat("Coldn't read 'this' from the target: %s", read_error.AsCString());
            return false;
        }
        
        DataExtractor extractor(data.GetBytes(), data.GetByteSize(), address_byte_order, address_byte_size);
        
        uint32_t offset = 0;
        
        object_ptr = extractor.GetPointer(&offset);
        
        return true;
    }
    else
    {
        err.SetErrorString("'this' is not in memory; LLDB must be extended to handle registers");
        return false;
    }
}

bool 
ClangExpressionDeclMap::Dematerialize (ExecutionContext *exe_ctx,
                                       ClangExpressionVariable *&result,
                                       Error &err)
{
    return DoMaterialize(true, exe_ctx, &result, err);
}

bool
ClangExpressionDeclMap::DumpMaterializedStruct(ExecutionContext *exe_ctx, 
                                               Stream &s,
                                               Error &err)
{
    if (!m_struct_laid_out)
    {
        err.SetErrorString("Structure hasn't been laid out yet");
        return false;
    }
    
    if (!exe_ctx)
    {
        err.SetErrorString("Received null execution context");
        return false;
    }
    
    
    if (!exe_ctx->process)
    {
        err.SetErrorString("Couldn't find the process");
        return false;
    }
    
    if (!exe_ctx->target)
    {
        err.SetErrorString("Couldn't find the target");
        return false;
    }
    
    lldb::DataBufferSP data(new DataBufferHeap(m_struct_size, 0));    
    
    Error error;
    if (exe_ctx->process->ReadMemory (m_materialized_location, data->GetBytes(), data->GetByteSize(), error) != data->GetByteSize())
    {
        err.SetErrorStringWithFormat ("Couldn't read struct from the target: %s", error.AsCString());
        return false;
    }
    
    DataExtractor extractor(data, exe_ctx->process->GetByteOrder(), exe_ctx->target->GetArchitecture().GetAddressByteSize());
    
    for (uint64_t member_index = 0, num_members = m_struct_members.Size();
         member_index < num_members;
         ++member_index)
    {
        ClangExpressionVariable &member (m_struct_members.VariableAtIndex(member_index));
        
        s.Printf("[%s]\n", member.m_name.c_str());
        
        if (!member.m_jit_vars.get())
            return false;
        
        extractor.Dump(&s,                                                      // stream
                       member.m_jit_vars->m_offset,                             // offset
                       lldb::eFormatBytesWithASCII,                             // format
                       1,                                                       // byte size of individual entries
                       member.m_jit_vars->m_size,                               // number of entries
                       16,                                                      // entries per line
                       m_materialized_location + member.m_jit_vars->m_offset,   // address to print
                       0,                                                       // bit size (bitfields only; 0 means ignore)
                       0);                                                      // bit alignment (bitfields only; 0 means ignore)
        
        s.PutChar('\n');
    }
    
    return true;
}

bool 
ClangExpressionDeclMap::DoMaterialize (bool dematerialize,
                                       ExecutionContext *exe_ctx,
                                       ClangExpressionVariable **result,
                                       Error &err)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    if (!m_struct_laid_out)
    {
        err.SetErrorString("Structure hasn't been laid out yet");
        return LLDB_INVALID_ADDRESS;
    }
    
    if (!exe_ctx)
    {
        err.SetErrorString("Received null execution context");
        return LLDB_INVALID_ADDRESS;
    }
    
    if (!exe_ctx->frame)
    {
        err.SetErrorString("Received null execution frame");
        return LLDB_INVALID_ADDRESS;
    }
    
    if (!m_struct_size)
    {
        if (log)
            log->PutCString("Not bothering to allocate a struct because no arguments are needed");
        
        m_allocated_area = NULL;
        
        return true;
    }
    
    const SymbolContext &sym_ctx(exe_ctx->frame->GetSymbolContext(lldb::eSymbolContextEverything));
    
    if (!dematerialize)
    {
        if (m_materialized_location)
        {
            exe_ctx->process->DeallocateMemory(m_materialized_location);
            m_materialized_location = 0;
        }
        
        if (log)
            log->PutCString("Allocating memory for materialized argument struct");
        
        lldb::addr_t mem = exe_ctx->process->AllocateMemory(m_struct_alignment + m_struct_size, 
                                                            lldb::ePermissionsReadable | lldb::ePermissionsWritable,
                                                            err);
        
        if (mem == LLDB_INVALID_ADDRESS)
            return false;
        
        m_allocated_area = mem;
    }
    
    m_materialized_location = m_allocated_area;
    
    if (m_materialized_location % m_struct_alignment)
        m_materialized_location += (m_struct_alignment - (m_materialized_location % m_struct_alignment));
    
    for (uint64_t member_index = 0, num_members = m_struct_members.Size();
         member_index < num_members;
         ++member_index)
    {
        ClangExpressionVariable &member (m_struct_members.VariableAtIndex(member_index));
        
        if (!member.m_parser_vars.get())
            return false;
        
        ClangExpressionVariable *entity = m_found_entities.GetVariable(member.m_parser_vars->m_named_decl);
        ClangExpressionVariable *persistent_variable = m_persistent_vars->GetVariable(member.m_name.c_str());
        
        if (entity)
        {
            if (!member.m_jit_vars.get())
                return false;
            
            if (!DoMaterializeOneVariable(dematerialize, *exe_ctx, sym_ctx, member.m_name.c_str(), member.m_user_type, m_materialized_location + member.m_jit_vars->m_offset, err))
                return false;
        }
        else if (persistent_variable)
        {
            if (!member.m_name.compare(m_result_name))
            {
                if (!dematerialize)
                    continue;
                
                if (log)
                    log->PutCString("Found result member in the struct");
                
                *result = &member;
            }
            
            if (log)
                log->Printf("Searched for persistent variable %s and found %s", member.m_name.c_str(), persistent_variable->m_name.c_str());
            
            if (!DoMaterializeOnePersistentVariable(dematerialize, *exe_ctx, persistent_variable->m_name.c_str(), m_materialized_location + member.m_jit_vars->m_offset, err))
                return false;
        }
        else
        {
            err.SetErrorStringWithFormat("Unexpected variable %s", member.m_name.c_str());
            return false;
        }
    }
    
    return true;
}

bool
ClangExpressionDeclMap::DoMaterializeOnePersistentVariable(bool dematerialize,
                                                           ExecutionContext &exe_ctx,
                                                           const char *name,
                                                           lldb::addr_t addr,
                                                           Error &err)
{    
    ClangExpressionVariable *pvar(m_persistent_vars->GetVariable(name));
    
    if (!pvar)
    {
        err.SetErrorStringWithFormat("Undefined persistent variable %s", name);
        return LLDB_INVALID_ADDRESS;
    }
    
    size_t pvar_size = pvar->Size();
    
    if (!pvar->m_data_sp.get())
        return false;
    
    uint8_t *pvar_data = pvar->m_data_sp->GetBytes();               
    Error error;
    
    if (dematerialize)
    {
        if (exe_ctx.process->ReadMemory (addr, pvar_data, pvar_size, error) != pvar_size)
        {
            err.SetErrorStringWithFormat ("Couldn't read a composite type from the target: %s", error.AsCString());
            return false;
        }
    }
    else 
    {
        if (exe_ctx.process->WriteMemory (addr, pvar_data, pvar_size, error) != pvar_size)
        {
            err.SetErrorStringWithFormat ("Couldn't write a composite type to the target: %s", error.AsCString());
            return false;
        }
    }
    
    return true;
}

bool 
ClangExpressionDeclMap::DoMaterializeOneVariable(bool dematerialize,
                                                 ExecutionContext &exe_ctx,
                                                 const SymbolContext &sym_ctx,
                                                 const char *name,
                                                 TypeFromUser type,
                                                 lldb::addr_t addr, 
                                                 Error &err)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    if (!exe_ctx.frame || !exe_ctx.process)
        return false;
    
    Variable *var = FindVariableInScope(*exe_ctx.frame, name, &type);
    
    if (!var)
    {
        err.SetErrorStringWithFormat("Couldn't find %s with appropriate type", name);
        return false;
    }
    
    if (log)
        log->Printf("%s %s with type %p", (dematerialize ? "Dematerializing" : "Materializing"), name, type.GetOpaqueQualType());
    
    std::auto_ptr<lldb_private::Value> location_value(GetVariableValue(exe_ctx,
                                                                       var,
                                                                       type.GetASTContext()));
    
    if (!location_value.get())
    {
        err.SetErrorStringWithFormat("Couldn't get value for %s", name);
        return false;
    }

    // The size of the type contained in addr
    
    size_t addr_bit_size = ClangASTType::GetClangTypeBitWidth(type.GetASTContext(), type.GetOpaqueQualType());
    size_t addr_byte_size = addr_bit_size % 8 ? ((addr_bit_size + 8) / 8) : (addr_bit_size / 8);
    
    Value::ValueType value_type = location_value->GetValueType();
    
    switch (value_type)
    {
    default:
        {
            StreamString ss;
            
            location_value->Dump(&ss);
            
            err.SetErrorStringWithFormat("%s has a value of unhandled type: %s", name, ss.GetString().c_str());
            return false;
        }
        break;
    case Value::eValueTypeLoadAddress:
        {
            lldb::addr_t value_addr = location_value->GetScalar().ULongLong();
            
            DataBufferHeap data;
            data.SetByteSize(addr_byte_size);
            
            lldb::addr_t src_addr;
            lldb::addr_t dest_addr;
            
            if (dematerialize)
            {
                src_addr = addr;
                dest_addr = value_addr;
            }
            else
            {
                src_addr = value_addr;
                dest_addr = addr;
            }
            
            Error error;
            if (exe_ctx.process->ReadMemory (src_addr, data.GetBytes(), addr_byte_size, error) != addr_byte_size)
            {
                err.SetErrorStringWithFormat ("Couldn't read %s from the target: %s", name, error.AsCString());
                return false;
            }
            
            if (exe_ctx.process->WriteMemory (dest_addr, data.GetBytes(), addr_byte_size, error) != addr_byte_size)
            {
                err.SetErrorStringWithFormat ("Couldn't write %s to the target: %s", name, error.AsCString());
                return false;
            }
            
            if (log)
                log->Printf("Copied from 0x%llx to 0x%llx", (uint64_t)src_addr, (uint64_t)addr);
        }
        break;
    case Value::eValueTypeScalar:
        {
            if (location_value->GetContextType() != Value::eContextTypeDCRegisterInfo)
            {
                StreamString ss;
                
                location_value->Dump(&ss);
                
                err.SetErrorStringWithFormat("%s is a scalar of unhandled type: %s", name, ss.GetString().c_str());
                return false;
            }
            
            lldb::RegisterInfo *register_info = location_value->GetRegisterInfo();
            
            if (!register_info)
            {
                err.SetErrorStringWithFormat("Couldn't get the register information for %s", name);
                return false;
            }
                        
            RegisterContext *register_context = exe_ctx.GetRegisterContext();
            
            if (!register_context)
            {
                err.SetErrorStringWithFormat("Couldn't read register context to read %s from %s", name, register_info->name);
                return false;
            }
            
            uint32_t register_number = register_info->kinds[lldb::eRegisterKindLLDB];
            uint32_t register_byte_size = register_info->byte_size;
            
            if (dematerialize)
            {
                // Moving from addr into a register
                //
                // Case 1: addr_byte_size and register_byte_size are the same
                //
                //   |AABBCCDD| Address contents
                //   |AABBCCDD| Register contents
                //
                // Case 2: addr_byte_size is bigger than register_byte_size
                //
                //   Error!  (The register should always be big enough to hold the data)
                //
                // Case 3: register_byte_size is bigger than addr_byte_size
                //
                //   |AABB| Address contents
                //   |AABB0000| Register contents [on little-endian hardware]
                //   |0000AABB| Register contents [on big-endian hardware]
                
                if (addr_byte_size > register_byte_size)
                {
                    err.SetErrorStringWithFormat("%s is too big to store in %s", name, register_info->name);
                    return false;
                }
            
                uint32_t register_offset;
                
                switch (exe_ctx.process->GetByteOrder())
                {
                default:
                    err.SetErrorStringWithFormat("%s is stored with an unhandled byte order", name);
                    return false;
                case lldb::eByteOrderLittle:
                    register_offset = 0;
                    break;
                case lldb::eByteOrderBig:
                    register_offset = register_byte_size - addr_byte_size;
                    break;
                }
                
                DataBufferHeap register_data (register_byte_size, 0);
                
                Error error;
                if (exe_ctx.process->ReadMemory (addr, register_data.GetBytes() + register_offset, addr_byte_size, error) != addr_byte_size)
                {
                    err.SetErrorStringWithFormat ("Couldn't read %s from the target: %s", name, error.AsCString());
                    return false;
                }
                
                DataExtractor register_extractor (register_data.GetBytes(), register_byte_size, exe_ctx.process->GetByteOrder(), exe_ctx.process->GetAddressByteSize());
                
                if (!register_context->WriteRegisterBytes(register_number, register_extractor, 0))
                {
                    err.SetErrorStringWithFormat("Couldn't read %s from %s", name, register_info->name);
                    return false;
                }
            }
            else
            {
                // Moving from a register into addr
                //
                // Case 1: addr_byte_size and register_byte_size are the same
                //
                //   |AABBCCDD| Register contents
                //   |AABBCCDD| Address contents
                //
                // Case 2: addr_byte_size is bigger than register_byte_size
                //
                //   Error!  (The register should always be big enough to hold the data)
                //
                // Case 3: register_byte_size is bigger than addr_byte_size
                //
                //   |AABBCCDD| Register contents
                //   |AABB|     Address contents on little-endian hardware
                //       |CCDD| Address contents on big-endian hardware
                
                if (addr_byte_size > register_byte_size)
                {
                    err.SetErrorStringWithFormat("%s is too big to store in %s", name, register_info->name);
                    return false;
                }
                
                uint32_t register_offset;
                
                switch (exe_ctx.process->GetByteOrder())
                {
                    default:
                        err.SetErrorStringWithFormat("%s is stored with an unhandled byte order", name);
                        return false;
                    case lldb::eByteOrderLittle:
                        register_offset = 0;
                        break;
                    case lldb::eByteOrderBig:
                        register_offset = register_byte_size - addr_byte_size;
                        break;
                }
                
                DataExtractor register_extractor;
                
                if (!register_context->ReadRegisterBytes(register_number, register_extractor))
                {
                    err.SetErrorStringWithFormat("Couldn't read %s from %s", name, register_info->name);
                    return false;
                }
                
                const void *register_data = register_extractor.GetData(&register_offset, addr_byte_size);
                
                if (!register_data)
                {
                    err.SetErrorStringWithFormat("Read but couldn't extract data for %s from %s", name, register_info->name);
                    return false;
                }
                
                Error error;
                if (exe_ctx.process->WriteMemory (addr, register_data, addr_byte_size, error) != addr_byte_size)
                {
                    err.SetErrorStringWithFormat ("Couldn't write %s to the target: %s", error.AsCString());
                    return false;
                }
            }
        }
    }
    
    return true;
}

Variable *
ClangExpressionDeclMap::FindVariableInScope(StackFrame &frame,
                                            const char *name,
                                            TypeFromUser *type)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    ConstString name_cs(name);
    
    VariableList *var_list = frame.GetVariableList(true);
    
    lldb::VariableSP var = var_list->FindVariable(name_cs);
    
    if (!var)
        return NULL;
    
    if (!type)
        return var.get();
    
    if (type->GetASTContext() == var->GetType()->GetClangAST())
    {
        if (!ClangASTContext::AreTypesSame(type->GetASTContext(), type->GetOpaqueQualType(), var->GetType()->GetClangType()))
            return NULL;
    }
    else
    {
        if (log)
            log->PutCString("Skipping a candidate variable because of different AST contexts");
        return NULL;
    }
    
    return var.get();
    
    return NULL;
}

// Interface for ClangASTSource
void 
ClangExpressionDeclMap::GetDecls(NameSearchContext &context,
                                 const char *name)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
        
    if (log)
        log->Printf("Hunting for a definition for %s", name);
    
    // Back out in all cases where we're not fully initialized
    if (!m_exe_ctx || !m_exe_ctx->frame || !m_sym_ctx)
        return;
        
    ConstString name_cs(name);
    
    if (!strcmp(name, "___clang_class"))
    {
        // Clang is looking for the type of "this"
        
        VariableList *vars = m_exe_ctx->frame->GetVariableList(false);
        
        if (!vars)
            return;
        
        lldb::VariableSP this_var = vars->FindVariable(ConstString("this"));
        
        if (!this_var)
            return;
        
        Type *this_type = this_var->GetType();
        
        if (!this_type)
            return;
        
        TypeFromUser this_user_type(this_type->GetClangType(),
                                    this_type->GetClangAST());
        
        m_object_pointer_type = this_user_type;
        
        void *pointer_target_type;
        
        if (!ClangASTContext::IsPointerType(this_user_type.GetOpaqueQualType(),
                                            &pointer_target_type))
            return;
        
        TypeFromUser class_user_type(pointer_target_type,
                                     this_type->GetClangAST());

        AddOneType(context, class_user_type, true);
        
        return;
    }
    
    SymbolContextList sym_ctxs;
    
    m_sym_ctx->FindFunctionsByName(name_cs, false, sym_ctxs);
    
    bool found_specific = false;
    Symbol *generic_symbol = NULL;
    Symbol *non_extern_symbol = NULL;
    
    for (uint32_t index = 0, num_indices = sym_ctxs.GetSize();
         index < num_indices;
         ++index)
    {
        SymbolContext sym_ctx;
        sym_ctxs.GetContextAtIndex(index, sym_ctx);

        if (sym_ctx.function)
        {
            // TODO only do this if it's a C function; C++ functions may be
            // overloaded
            if (!found_specific)
                AddOneFunction(context, sym_ctx.function, NULL);
            found_specific = true;
        }
        else if (sym_ctx.symbol)
        {
            if (sym_ctx.symbol->IsExternal())
                generic_symbol = sym_ctx.symbol;
            else
                non_extern_symbol = sym_ctx.symbol;
        }
    }
    
    if (!found_specific)
    {
        if (generic_symbol)
            AddOneFunction(context, NULL, generic_symbol);
        else if (non_extern_symbol)
            AddOneFunction(context, NULL, non_extern_symbol);
    }
    
    Variable *var = FindVariableInScope(*m_exe_ctx->frame, name);
    
    if (var)
        AddOneVariable(context, var);
    
    ClangExpressionVariable *pvar(m_persistent_vars->GetVariable(name));
    
    if (pvar)
        AddOneVariable(context, pvar);
    
    
    // See information on gating of this operation next to the definition for
    // m_lookedup_types.
    
    const char *name_uniq = name_cs.GetCString();
    
    if (m_lookedup_types.find(name_uniq) == m_lookedup_types.end())
    {
        // 1 The name is added to m_lookedup_types.
        m_lookedup_types.insert(std::pair<const char*, bool>(name_uniq, true));
        
        // 2 The type is looked up and added, potentially causing more type loookups.
        lldb::TypeSP type = m_sym_ctx->FindTypeByName(name_cs);
        
        if (type.get())
        {
            TypeFromUser user_type(type->GetClangType(),
                                   type->GetClangAST());
            
            AddOneType(context, user_type, false);
        }
        
        // 3 The name is removed from m_lookedup_types.
        m_lookedup_types.erase(name_uniq);
    }
    
}
        
Value *
ClangExpressionDeclMap::GetVariableValue(ExecutionContext &exe_ctx,
                                         Variable *var,
                                         clang::ASTContext *parser_ast_context,
                                         TypeFromUser *user_type,
                                         TypeFromParser *parser_type)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    Type *var_type = var->GetType();
    
    if (!var_type) 
    {
        if (log)
            log->PutCString("Skipped a definition because it has no type");
        return NULL;
    }
    
    void *var_opaque_type = var_type->GetClangType();
    
    if (!var_opaque_type)
    {
        if (log)
            log->PutCString("Skipped a definition because it has no Clang type");
        return NULL;
    }
    
    TypeList *type_list = var_type->GetTypeList();
    
    if (!type_list)
    {
        if (log)
            log->PutCString("Skipped a definition because the type has no associated type list");
        return NULL;
    }
    
    clang::ASTContext *exe_ast_ctx = type_list->GetClangASTContext().getASTContext();
    
    if (!exe_ast_ctx)
    {
        if (log)
            log->PutCString("There is no AST context for the current execution context");
        return NULL;
    }
    
    DWARFExpression &var_location_expr = var->LocationExpression();
    
    std::auto_ptr<Value> var_location(new Value);
    
    lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
    
    if (var_location_expr.IsLocationList())
    {
        SymbolContext var_sc;
        var->CalculateSymbolContext (&var_sc);
        loclist_base_load_addr = var_sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress (exe_ctx.target);
    }
    Error err;
    
    if (!var_location_expr.Evaluate(&exe_ctx, exe_ast_ctx, loclist_base_load_addr, NULL, *var_location.get(), &err))
    {
        if (log)
            log->Printf("Error evaluating location: %s", err.AsCString());
        return NULL;
    }
    
    clang::ASTContext *var_ast_context = type_list->GetClangASTContext().getASTContext();
    
    void *type_to_use;
    
    if (parser_ast_context)
    {
        type_to_use = ClangASTContext::CopyType(parser_ast_context, var_ast_context, var_opaque_type);
        
        if (parser_type)
            *parser_type = TypeFromParser(type_to_use, parser_ast_context);
    }
    else
        type_to_use = var_opaque_type;
    
    if (var_location.get()->GetContextType() == Value::eContextTypeInvalid)
        var_location.get()->SetContext(Value::eContextTypeOpaqueClangQualType, type_to_use);
    
    if (var_location.get()->GetValueType() == Value::eValueTypeFileAddress)
    {
        SymbolContext var_sc;
        var->CalculateSymbolContext(&var_sc);
        
        if (!var_sc.module_sp)
            return NULL;
        
        ObjectFile *object_file = var_sc.module_sp->GetObjectFile();
        
        if (!object_file)
            return NULL;
        
        Address so_addr(var_location->GetScalar().ULongLong(), object_file->GetSectionList());
        
        lldb::addr_t load_addr = so_addr.GetLoadAddress(m_exe_ctx->target);
        
        var_location->GetScalar() = load_addr;
        var_location->SetValueType(Value::eValueTypeLoadAddress);
    }
    
    if (user_type)
        *user_type = TypeFromUser(var_opaque_type, var_ast_context);
    
    return var_location.release();
}

void
ClangExpressionDeclMap::AddOneVariable(NameSearchContext &context,
                                       Variable* var)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    TypeFromUser ut;
    TypeFromParser pt;
    
    Value *var_location = GetVariableValue(*m_exe_ctx, 
                                           var, 
                                           context.GetASTContext(),
                                           &ut,
                                           &pt);
    
    NamedDecl *var_decl = context.AddVarDecl(pt.GetOpaqueQualType());
    
    ClangExpressionVariable &entity(m_found_entities.VariableAtIndex(m_found_entities.CreateVariable()));
    entity.m_name       = context.Name.getAsString();
    entity.m_user_type  = ut;
    
    entity.EnableParserVars();
    entity.m_parser_vars->m_parser_type = pt;
    entity.m_parser_vars->m_named_decl  = var_decl;
    entity.m_parser_vars->m_llvm_value  = NULL;
    entity.m_parser_vars->m_lldb_value  = var_location;
    
    if (log)
        log->Printf("Found variable %s, returned (NamedDecl)%p", context.Name.getAsString().c_str(), var_decl);    
}

void
ClangExpressionDeclMap::AddOneVariable(NameSearchContext &context,
                                       ClangExpressionVariable *pvar)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    TypeFromUser user_type = pvar->m_user_type;
    
    TypeFromParser parser_type(ClangASTContext::CopyType(context.GetASTContext(), 
                                                         user_type.GetASTContext(), 
                                                         user_type.GetOpaqueQualType()),
                               context.GetASTContext());
    
    NamedDecl *var_decl = context.AddVarDecl(parser_type.GetOpaqueQualType());
    
    pvar->EnableParserVars();
    pvar->m_parser_vars->m_parser_type = parser_type;
    pvar->m_parser_vars->m_named_decl  = var_decl;
    pvar->m_parser_vars->m_llvm_value  = NULL;
    pvar->m_parser_vars->m_lldb_value  = NULL;
    
    if (log)
        log->Printf("Added pvar %s, returned (NamedDecl)%p", pvar->m_name.c_str(), var_decl);  
}

void
ClangExpressionDeclMap::AddOneFunction(NameSearchContext &context,
                                       Function* fun,
                                       Symbol* symbol)
{
    Log *log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
    
    NamedDecl *fun_decl;
    std::auto_ptr<Value> fun_location(new Value);
    const Address *fun_address;
    
    // only valid for Functions, not for Symbols
    void *fun_opaque_type = NULL;
    clang::ASTContext *fun_ast_context = NULL;
    
    if (fun)
    {
#define BROKEN_OVERLOADING
        // Awaiting a fix on the Clang side
#ifndef BROKEN_OVERLOADING
        Type *fun_type = fun->GetType();
        
        if (!fun_type) 
        {
            if (log)
                log->PutCString("Skipped a function because it has no type");
            return;
        }
        
        fun_opaque_type = fun_type->GetClangType();
        
        if (!fun_opaque_type)
        {
            if (log)
                log->PutCString("Skipped a function because it has no Clang type");
            return;
        }
        
        fun_address = &fun->GetAddressRange().GetBaseAddress();
        
        TypeList *type_list = fun_type->GetTypeList();
        fun_ast_context = type_list->GetClangASTContext().getASTContext();
        void *copied_type = ClangASTContext::CopyType(context.GetASTContext(), fun_ast_context, fun_opaque_type);
        
        fun_decl = context.AddFunDecl(copied_type);
#else
        fun_address = &fun->GetAddressRange().GetBaseAddress();
        
        fun_decl = context.AddGenericFunDecl();
#endif
    }
    else if (symbol)
    {
        fun_address = &symbol->GetAddressRangeRef().GetBaseAddress();
        
        fun_decl = context.AddGenericFunDecl();
    }
    else
    {
        if (log)
            log->PutCString("AddOneFunction called with no function and no symbol");
        return;
    }
    
    lldb::addr_t load_addr = fun_address->GetLoadAddress(m_exe_ctx->target);
    fun_location->SetValueType(Value::eValueTypeLoadAddress);
    fun_location->GetScalar() = load_addr;
    
    ClangExpressionVariable &entity(m_found_entities.VariableAtIndex(m_found_entities.CreateVariable()));
    entity.m_name       = context.Name.getAsString();
    entity.m_user_type  = TypeFromUser(fun_opaque_type, fun_ast_context);;
    
    entity.EnableParserVars();
    entity.m_parser_vars->m_named_decl  = fun_decl;
    entity.m_parser_vars->m_llvm_value  = NULL;
    entity.m_parser_vars->m_lldb_value  = fun_location.release();
        
    if (log)
        log->Printf("Found %s function %s, returned (NamedDecl)%p", (fun ? "specific" : "generic"), context.Name.getAsString().c_str(), fun_decl);    
}

void 
ClangExpressionDeclMap::AddOneType(NameSearchContext &context, 
                                   TypeFromUser &ut,
                                   bool add_method)
{
    clang::ASTContext *parser_ast_context = context.GetASTContext();
    clang::ASTContext *user_ast_context = ut.GetASTContext();
    
    void *copied_type = ClangASTContext::CopyType(parser_ast_context, user_ast_context, ut.GetOpaqueQualType());
 
    TypeFromParser parser_type(copied_type, parser_ast_context);
    
    if (add_method && ClangASTContext::IsAggregateType(copied_type))
    {
        void *args[1];
        
        args[0] = ClangASTContext::GetVoidPtrType(parser_ast_context, false);
        
        void *method_type = ClangASTContext::CreateFunctionType (parser_ast_context,
                                                                 ClangASTContext::GetBuiltInType_void(parser_ast_context),
                                                                 args,
                                                                 1,
                                                                 false,
                                                                 ClangASTContext::GetTypeQualifiers(copied_type));

        const bool is_virtual = false;
        const bool is_static = false;
        const bool is_inline = false;
        const bool is_explicit = false;
        
        ClangASTContext::AddMethodToCXXRecordType (parser_ast_context,
                                                   copied_type,
                                                   "___clang_expr",
                                                   method_type,
                                                   lldb::eAccessPublic,
                                                   is_virtual,
                                                   is_static,
                                                   is_inline,
                                                   is_explicit);
    }
    
    context.AddTypeDecl(copied_type);
}