llvm-project/lldb/source/Expression/ClangUserExpression.cpp

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

// C Includes
#include <stdio.h>
#if HAVE_SYS_TYPES_H
#  include <sys/types.h>
#endif

// C++ Includes
#include <cstdlib>
#include <string>
#include <map>

#include "lldb/Core/ConstString.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/StreamFile.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Core/ValueObjectConstResult.h"
#include "lldb/Expression/ASTResultSynthesizer.h"
#include "lldb/Expression/ClangExpressionDeclMap.h"
#include "lldb/Expression/ClangExpressionParser.h"
#include "lldb/Expression/ClangFunction.h"
#include "lldb/Expression/ClangUserExpression.h"
#include "lldb/Expression/ExpressionSourceCode.h"
#include "lldb/Expression/IRExecutionUnit.h"
#include "lldb/Expression/IRInterpreter.h"
#include "lldb/Expression/Materializer.h"
#include "lldb/Host/Host.h"
#include "lldb/Symbol/Block.h"
#include "lldb/Symbol/ClangASTContext.h"
#include "lldb/Symbol/Function.h"
#include "lldb/Symbol/Type.h"
#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
#include "lldb/Symbol/VariableList.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/StackFrame.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/ThreadPlan.h"
#include "lldb/Target/ThreadPlanCallUserExpression.h"

#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"

using namespace lldb_private;

ClangUserExpression::ClangUserExpression (const char *expr,
                                          const char *expr_prefix,
                                          lldb::LanguageType language,
                                          ResultType desired_type) :
    ClangExpression (),
    m_stack_frame_bottom (LLDB_INVALID_ADDRESS),
    m_stack_frame_top (LLDB_INVALID_ADDRESS),
    m_expr_text (expr),
    m_expr_prefix (expr_prefix ? expr_prefix : ""),
    m_language (language),
    m_transformed_text (),
    m_desired_type (desired_type),
    m_enforce_valid_object (true),
    m_cplusplus (false),
    m_objectivec (false),
    m_static_method(false),
    m_needs_object_ptr (false),
    m_const_object (false),
    m_target (NULL),
    m_can_interpret (false),
    m_materialized_address (LLDB_INVALID_ADDRESS)
{
    switch (m_language)
    {
    case lldb::eLanguageTypeC_plus_plus:
        m_allow_cxx = true;
        break;
    case lldb::eLanguageTypeObjC:
        m_allow_objc = true;
        break;
    case lldb::eLanguageTypeObjC_plus_plus:
    default:
        m_allow_cxx = true;
        m_allow_objc = true;
        break;
    }
}

ClangUserExpression::~ClangUserExpression ()
{
}

clang::ASTConsumer *
ClangUserExpression::ASTTransformer (clang::ASTConsumer *passthrough)
{
    m_result_synthesizer.reset(new ASTResultSynthesizer(passthrough,
                                                        *m_target));
    
    return m_result_synthesizer.get();
}

void
ClangUserExpression::ScanContext(ExecutionContext &exe_ctx, Error &err)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    if (log)
        log->Printf("ClangUserExpression::ScanContext()");
    
    m_target = exe_ctx.GetTargetPtr();
    
    if (!(m_allow_cxx || m_allow_objc))
    {
        if (log)
            log->Printf("  [CUE::SC] Settings inhibit C++ and Objective-C");
        return;
    }
    
    StackFrame *frame = exe_ctx.GetFramePtr();
    if (frame == NULL)
    {
        if (log)
            log->Printf("  [CUE::SC] Null stack frame");
        return;
    }
    
    SymbolContext sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction | lldb::eSymbolContextBlock);
    
    if (!sym_ctx.function)
    {
        if (log)
            log->Printf("  [CUE::SC] Null function");
        return;
    }
    
    // Find the block that defines the function represented by "sym_ctx"
    Block *function_block = sym_ctx.GetFunctionBlock();
    
    if (!function_block)
    {
        if (log)
            log->Printf("  [CUE::SC] Null function block");
        return;
    }

    clang::DeclContext *decl_context = function_block->GetClangDeclContext();

    if (!decl_context)
    {
        if (log)
            log->Printf("  [CUE::SC] Null decl context");
        return;
    }
    
    if (clang::CXXMethodDecl *method_decl = llvm::dyn_cast<clang::CXXMethodDecl>(decl_context))
    {
        if (m_allow_cxx && method_decl->isInstance())
        {
            if (m_enforce_valid_object)
            {
                lldb::VariableListSP variable_list_sp (function_block->GetBlockVariableList (true));
                
                const char *thisErrorString = "Stopped in a C++ method, but 'this' isn't available; pretending we are in a generic context";
                
                if (!variable_list_sp)
                {
                    err.SetErrorString(thisErrorString);
                    return;
                }
                
                lldb::VariableSP this_var_sp (variable_list_sp->FindVariable(ConstString("this")));
                
                if (!this_var_sp ||
                    !this_var_sp->IsInScope(frame) || 
                    !this_var_sp->LocationIsValidForFrame (frame))
                {
                    err.SetErrorString(thisErrorString);
                    return;
                }
            }
            
            m_cplusplus = true;
            m_needs_object_ptr = true;
        }
    }
    else if (clang::ObjCMethodDecl *method_decl = llvm::dyn_cast<clang::ObjCMethodDecl>(decl_context))
    {        
        if (m_allow_objc)
        {
            if (m_enforce_valid_object)
            {
                lldb::VariableListSP variable_list_sp (function_block->GetBlockVariableList (true));
                
                const char *selfErrorString = "Stopped in an Objective-C method, but 'self' isn't available; pretending we are in a generic context";
                
                if (!variable_list_sp)
                {
                    err.SetErrorString(selfErrorString);
                    return;
                }
                
                lldb::VariableSP self_variable_sp = variable_list_sp->FindVariable(ConstString("self"));
                
                if (!self_variable_sp || 
                    !self_variable_sp->IsInScope(frame) || 
                    !self_variable_sp->LocationIsValidForFrame (frame))
                {
                    err.SetErrorString(selfErrorString);
                    return;
                }
            }
            
            m_objectivec = true;
            m_needs_object_ptr = true;
            
            if (!method_decl->isInstanceMethod())
                m_static_method = true;
        }
    }
    else if (clang::FunctionDecl *function_decl = llvm::dyn_cast<clang::FunctionDecl>(decl_context))
    {
        // We might also have a function that said in the debug information that it captured an
        // object pointer.  The best way to deal with getting to the ivars at present it by pretending
        // that this is a method of a class in whatever runtime the debug info says the object pointer
        // belongs to.  Do that here.
        
        ClangASTMetadata *metadata = ClangASTContext::GetMetadata (&decl_context->getParentASTContext(), function_decl);
        if (metadata && metadata->HasObjectPtr())
        {
            lldb::LanguageType language = metadata->GetObjectPtrLanguage();
            if (language == lldb::eLanguageTypeC_plus_plus)
            {
                if (m_enforce_valid_object)
                {
                    lldb::VariableListSP variable_list_sp (function_block->GetBlockVariableList (true));
                    
                    const char *thisErrorString = "Stopped in a context claiming to capture a C++ object pointer, but 'this' isn't available; pretending we are in a generic context";
                    
                    if (!variable_list_sp)
                    {
                        err.SetErrorString(thisErrorString);
                        return;
                    }
                    
                    lldb::VariableSP this_var_sp (variable_list_sp->FindVariable(ConstString("this")));
                    
                    if (!this_var_sp ||
                        !this_var_sp->IsInScope(frame) ||
                        !this_var_sp->LocationIsValidForFrame (frame))
                    {
                        err.SetErrorString(thisErrorString);
                        return;
                    }
                }
                
                m_cplusplus = true;
                m_needs_object_ptr = true;
            }
            else if (language == lldb::eLanguageTypeObjC)
            {
                if (m_enforce_valid_object)
                {
                    lldb::VariableListSP variable_list_sp (function_block->GetBlockVariableList (true));
                    
                    const char *selfErrorString = "Stopped in a context claiming to capture an Objective-C object pointer, but 'self' isn't available; pretending we are in a generic context";
                    
                    if (!variable_list_sp)
                    {
                        err.SetErrorString(selfErrorString);
                        return;
                    }
                    
                    lldb::VariableSP self_variable_sp = variable_list_sp->FindVariable(ConstString("self"));
                    
                    if (!self_variable_sp ||
                        !self_variable_sp->IsInScope(frame) ||
                        !self_variable_sp->LocationIsValidForFrame (frame))
                    {
                        err.SetErrorString(selfErrorString);
                        return;
                    }
                    
                    Type *self_type = self_variable_sp->GetType();
                    
                    if (!self_type)
                    {
                        err.SetErrorString(selfErrorString);
                        return;
                    }
                    
                    ClangASTType self_clang_type = self_type->GetClangForwardType();
                    
                    if (!self_clang_type)
                    {
                        err.SetErrorString(selfErrorString);
                        return;
                    }
                                        
                    if (self_clang_type.IsObjCClassType())
                    {
                        return;
                    }
                    else if (self_clang_type.IsObjCObjectPointerType())
                    {
                        m_objectivec = true;
                        m_needs_object_ptr = true;
                    }
                    else
                    {
                        err.SetErrorString(selfErrorString);
                        return;
                    }
                }
                else
                {
                    m_objectivec = true;
                    m_needs_object_ptr = true;
                }
            }
        }
    }
}

void
ClangUserExpression::InstallContext (ExecutionContext &exe_ctx)
{
    m_process_wp = exe_ctx.GetProcessSP();
    
    lldb::StackFrameSP frame_sp = exe_ctx.GetFrameSP();
    
    if (frame_sp)
        m_address = frame_sp->GetFrameCodeAddress();
}

bool
ClangUserExpression::LockAndCheckContext (ExecutionContext &exe_ctx,
                                          lldb::TargetSP &target_sp,
                                          lldb::ProcessSP &process_sp,
                                          lldb::StackFrameSP &frame_sp)
{
    lldb::ProcessSP expected_process_sp = m_process_wp.lock();
    process_sp = exe_ctx.GetProcessSP();

    if (process_sp != expected_process_sp)
        return false;
    
    process_sp = exe_ctx.GetProcessSP();
    target_sp = exe_ctx.GetTargetSP();
    frame_sp = exe_ctx.GetFrameSP();
    
    if (m_address.IsValid())
    {
        if (!frame_sp)
            return false;
        else
            return (0 == Address::CompareLoadAddress(m_address, frame_sp->GetFrameCodeAddress(), target_sp.get()));
    }
    
    return true;
}

bool
ClangUserExpression::MatchesContext (ExecutionContext &exe_ctx)
{
    lldb::TargetSP target_sp;
    lldb::ProcessSP process_sp;
    lldb::StackFrameSP frame_sp;
    
    return LockAndCheckContext(exe_ctx, target_sp, process_sp, frame_sp);
}

// This is a really nasty hack, meant to fix Objective-C expressions of the form
// (int)[myArray count].  Right now, because the type information for count is
// not available, [myArray count] returns id, which can't be directly cast to
// int without causing a clang error.
static void
ApplyObjcCastHack(std::string &expr)
{
#define OBJC_CAST_HACK_FROM "(int)["
#define OBJC_CAST_HACK_TO   "(int)(long long)["

    size_t from_offset;
    
    while ((from_offset = expr.find(OBJC_CAST_HACK_FROM)) != expr.npos)
        expr.replace(from_offset, sizeof(OBJC_CAST_HACK_FROM) - 1, OBJC_CAST_HACK_TO);

#undef OBJC_CAST_HACK_TO
#undef OBJC_CAST_HACK_FROM
}

// Another hack, meant to allow use of unichar despite it not being available in
// the type information.  Although we could special-case it in type lookup,
// hopefully we'll figure out a way to #include the same environment as is
// present in the original source file rather than try to hack specific type
// definitions in as needed.
static void
ApplyUnicharHack(std::string &expr)
{
#define UNICHAR_HACK_FROM "unichar"
#define UNICHAR_HACK_TO   "unsigned short"
    
    size_t from_offset;
    
    while ((from_offset = expr.find(UNICHAR_HACK_FROM)) != expr.npos)
        expr.replace(from_offset, sizeof(UNICHAR_HACK_FROM) - 1, UNICHAR_HACK_TO);
    
#undef UNICHAR_HACK_TO
#undef UNICHAR_HACK_FROM
}

bool
ClangUserExpression::Parse (Stream &error_stream, 
                            ExecutionContext &exe_ctx,
                            lldb_private::ExecutionPolicy execution_policy,
                            bool keep_result_in_memory)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
    
    Error err;
 
    InstallContext(exe_ctx);
    
    ScanContext(exe_ctx, err);
    
    if (!err.Success())
    {
        error_stream.Printf("warning: %s\n", err.AsCString());
    }
    
    StreamString m_transformed_stream;
    
    ////////////////////////////////////
    // Generate the expression
    //
    
    ApplyObjcCastHack(m_expr_text);
    //ApplyUnicharHack(m_expr_text);

    std::unique_ptr<ExpressionSourceCode> source_code (ExpressionSourceCode::CreateWrapped(m_expr_prefix.c_str(), m_expr_text.c_str()));
    
    lldb::LanguageType lang_type;
    
    if (m_cplusplus)
        lang_type = lldb::eLanguageTypeC_plus_plus;
    else if(m_objectivec)
        lang_type = lldb::eLanguageTypeObjC;
    else
        lang_type = lldb::eLanguageTypeC;
    
    if (!source_code->GetText(m_transformed_text, lang_type, m_const_object, m_static_method))
    {
        error_stream.PutCString ("error: couldn't construct expression body");
        return false;
    }
    
    if (log)
        log->Printf("Parsing the following code:\n%s", m_transformed_text.c_str());
    
    ////////////////////////////////////
    // Set up the target and compiler
    //
    
    Target *target = exe_ctx.GetTargetPtr();
    
    if (!target)
    {
        error_stream.PutCString ("error: invalid target\n");
        return false;
    }
    
    //////////////////////////
    // Parse the expression
    //
        
    m_materializer_ap.reset(new Materializer());
        
    m_expr_decl_map.reset(new ClangExpressionDeclMap(keep_result_in_memory, exe_ctx));
    
    class OnExit
    {
    public:
        typedef std::function <void (void)> Callback;
        
        OnExit (Callback const &callback) :
            m_callback(callback)
        {
        }
        
        ~OnExit ()
        {
            m_callback();
        }
    private:
        Callback m_callback;
    };
    
    OnExit on_exit([this]() { m_expr_decl_map.reset(); });
    
    if (!m_expr_decl_map->WillParse(exe_ctx, m_materializer_ap.get()))
    {
        error_stream.PutCString ("error: current process state is unsuitable for expression parsing\n");
        
        m_expr_decl_map.reset(); // We are being careful here in the case of breakpoint conditions.
        
        return false;
    }
    
    Process *process = exe_ctx.GetProcessPtr();
    ExecutionContextScope *exe_scope = process;
    
    if (!exe_scope)
        exe_scope = exe_ctx.GetTargetPtr();
    
    ClangExpressionParser parser(exe_scope, *this);
    
    unsigned num_errors = parser.Parse (error_stream);
    
    if (num_errors)
    {
        error_stream.Printf ("error: %d errors parsing expression\n", num_errors);
        
        m_expr_decl_map.reset(); // We are being careful here in the case of breakpoint conditions.
        
        return false;
    }
    
    //////////////////////////////////////////////////////////////////////////////////////////
    // Prepare the output of the parser for execution, evaluating it statically if possible
    //
            
    Error jit_error = parser.PrepareForExecution (m_jit_start_addr,
                                                  m_jit_end_addr,
                                                  m_execution_unit_ap,
                                                  exe_ctx,
                                                  m_can_interpret,
                                                  execution_policy);
    
    m_expr_decl_map.reset(); // Make this go away since we don't need any of its state after parsing.  This also gets rid of any ClangASTImporter::Minions.
        
    if (jit_error.Success())
    {
        if (process && m_jit_start_addr != LLDB_INVALID_ADDRESS)
            m_jit_process_wp = lldb::ProcessWP(process->shared_from_this());
        return true;
    }
    else
    {
        const char *error_cstr = jit_error.AsCString();
        if (error_cstr && error_cstr[0])
            error_stream.Printf ("error: %s\n", error_cstr);
        else
            error_stream.Printf ("error: expression can't be interpreted or run\n");
        return false;
    }
}

static lldb::addr_t
GetObjectPointer (lldb::StackFrameSP frame_sp,
                  ConstString &object_name,
                  Error &err)
{
    err.Clear();
    
    if (!frame_sp)
    {
        err.SetErrorStringWithFormat("Couldn't load '%s' because the context is incomplete", object_name.AsCString());
        return LLDB_INVALID_ADDRESS;
    }
    
    lldb::VariableSP var_sp;
    lldb::ValueObjectSP valobj_sp;
    
    valobj_sp = frame_sp->GetValueForVariableExpressionPath(object_name.AsCString(),
                                                            lldb::eNoDynamicValues,
                                                            StackFrame::eExpressionPathOptionCheckPtrVsMember ||
                                                            StackFrame::eExpressionPathOptionsAllowDirectIVarAccess ||
                                                            StackFrame::eExpressionPathOptionsNoFragileObjcIvar ||
                                                            StackFrame::eExpressionPathOptionsNoSyntheticChildren ||
                                                            StackFrame::eExpressionPathOptionsNoSyntheticArrayRange,
                                                            var_sp,
                                                            err);
    
    if (!err.Success())
        return LLDB_INVALID_ADDRESS;
    
    lldb::addr_t ret = valobj_sp->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
    
    if (ret == LLDB_INVALID_ADDRESS)
    {
        err.SetErrorStringWithFormat("Couldn't load '%s' because its value couldn't be evaluated", object_name.AsCString());
        return LLDB_INVALID_ADDRESS;
    }
    
    return ret;
}

bool
ClangUserExpression::PrepareToExecuteJITExpression (Stream &error_stream,
                                                    ExecutionContext &exe_ctx,
                                                    lldb::addr_t &struct_address,
                                                    lldb::addr_t &object_ptr,
                                                    lldb::addr_t &cmd_ptr)
{
    lldb::TargetSP target;
    lldb::ProcessSP process;
    lldb::StackFrameSP frame;
    
    if (!LockAndCheckContext(exe_ctx,
                             target,
                             process, 
                             frame))
    {
        error_stream.Printf("The context has changed before we could JIT the expression!\n");
        return false;
    }
    
    if (m_jit_start_addr != LLDB_INVALID_ADDRESS || m_can_interpret)
    {        
        if (m_needs_object_ptr)
        {
            ConstString object_name;
            
            if (m_cplusplus)
            {
                object_name.SetCString("this");
            }
            else if (m_objectivec)
            {
                object_name.SetCString("self");
            }
            else
            {
                error_stream.Printf("Need object pointer but don't know the language\n");
                return false;
            }
            
            Error object_ptr_error;
            
            object_ptr = GetObjectPointer(frame, object_name, object_ptr_error);
            
            if (!object_ptr_error.Success())
            {
                error_stream.Printf("warning: couldn't get required object pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
                object_ptr = 0;
            }
            
            if (m_objectivec)
            {
                ConstString cmd_name("_cmd");
                
                cmd_ptr = GetObjectPointer(frame, cmd_name, object_ptr_error);
                
                if (!object_ptr_error.Success())
                {
                    error_stream.Printf("warning: couldn't get cmd pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
                    cmd_ptr = 0;
                }
            }
        }
        
        if (m_materialized_address == LLDB_INVALID_ADDRESS)
        {
            Error alloc_error;
            
            IRMemoryMap::AllocationPolicy policy = m_can_interpret ? IRMemoryMap::eAllocationPolicyHostOnly : IRMemoryMap::eAllocationPolicyMirror;
            
            m_materialized_address = m_execution_unit_ap->Malloc(m_materializer_ap->GetStructByteSize(),
                                                                 m_materializer_ap->GetStructAlignment(),
                                                                 lldb::ePermissionsReadable | lldb::ePermissionsWritable,
                                                                 policy,
                                                                 alloc_error);
            
            if (!alloc_error.Success())
            {
                error_stream.Printf("Couldn't allocate space for materialized struct: %s\n", alloc_error.AsCString());
                return false;
            }
        }
        
        struct_address = m_materialized_address;
        
        if (m_can_interpret && m_stack_frame_bottom == LLDB_INVALID_ADDRESS)
        {
            Error alloc_error;

            const size_t stack_frame_size = 512 * 1024;
            
            m_stack_frame_bottom = m_execution_unit_ap->Malloc(stack_frame_size,
                                                               8,
                                                               lldb::ePermissionsReadable | lldb::ePermissionsWritable,
                                                               IRMemoryMap::eAllocationPolicyHostOnly,
                                                               alloc_error);
            
            m_stack_frame_top = m_stack_frame_bottom + stack_frame_size;
            
            if (!alloc_error.Success())
            {
                error_stream.Printf("Couldn't allocate space for the stack frame: %s\n", alloc_error.AsCString());
                return false;
            }
        }
                
        Error materialize_error;
        
        m_dematerializer_sp = m_materializer_ap->Materialize(frame, *m_execution_unit_ap, struct_address, materialize_error);
        
        if (!materialize_error.Success())
        {
            error_stream.Printf("Couldn't materialize struct: %s\n", materialize_error.AsCString());
            return false;
        }
    }
    return true;
}

bool
ClangUserExpression::FinalizeJITExecution (Stream &error_stream,
                                           ExecutionContext &exe_ctx,
                                           lldb::ClangExpressionVariableSP &result,
                                           lldb::addr_t function_stack_bottom,
                                           lldb::addr_t function_stack_top)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
    
    if (log)
        log->Printf("-- [ClangUserExpression::FinalizeJITExecution] Dematerializing after execution --");
        
    if (!m_dematerializer_sp)
    {
        error_stream.Printf ("Couldn't apply expression side effects : no dematerializer is present");
        return false;
    }
    
    Error dematerialize_error;
    
    m_dematerializer_sp->Dematerialize(dematerialize_error, result, function_stack_bottom, function_stack_top);

    if (!dematerialize_error.Success())
    {
        error_stream.Printf ("Couldn't apply expression side effects : %s\n", dematerialize_error.AsCString("unknown error"));
        return false;
    }
        
    if (result)
        result->TransferAddress();
    
    m_dematerializer_sp.reset();
    
    return true;
}        

ExecutionResults
ClangUserExpression::Execute (Stream &error_stream,
                              ExecutionContext &exe_ctx,
                              const EvaluateExpressionOptions& options,
                              ClangUserExpression::ClangUserExpressionSP &shared_ptr_to_me,
                              lldb::ClangExpressionVariableSP &result)
{
    // The expression log is quite verbose, and if you're just tracking the execution of the
    // expression, it's quite convenient to have these logs come out with the STEP log as well.
    Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));

    if (m_jit_start_addr != LLDB_INVALID_ADDRESS || m_can_interpret)
    {
        lldb::addr_t struct_address = LLDB_INVALID_ADDRESS;
                
        lldb::addr_t object_ptr = 0;
        lldb::addr_t cmd_ptr = 0;
        
        if (!PrepareToExecuteJITExpression (error_stream, exe_ctx, struct_address, object_ptr, cmd_ptr))
        {
            error_stream.Printf("Errored out in %s, couldn't PrepareToExecuteJITExpression", __FUNCTION__);
            return eExecutionSetupError;
        }
        
        lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS;
        lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS;
        
        if (m_can_interpret)
        {            
            llvm::Module *module = m_execution_unit_ap->GetModule();
            llvm::Function *function = m_execution_unit_ap->GetFunction();
            
            if (!module || !function)
            {
                error_stream.Printf("Supposed to interpret, but nothing is there");
                return eExecutionSetupError;
            }

            Error interpreter_error;
            
            llvm::SmallVector <lldb::addr_t, 3> args;
            
            if (m_needs_object_ptr)
            {
                args.push_back(object_ptr);
                
                if (m_objectivec)
                    args.push_back(cmd_ptr);
            }
            
            args.push_back(struct_address);
            
            function_stack_bottom = m_stack_frame_bottom;
            function_stack_top = m_stack_frame_top;
            
            IRInterpreter::Interpret (*module,
                                      *function,
                                      args,
                                      *m_execution_unit_ap.get(),
                                      interpreter_error,
                                      function_stack_bottom,
                                      function_stack_top);
            
            if (!interpreter_error.Success())
            {
                error_stream.Printf("Supposed to interpret, but failed: %s", interpreter_error.AsCString());
                return eExecutionDiscarded;
            }
        }
        else
        {
            Address wrapper_address (m_jit_start_addr);
            
            llvm::SmallVector <lldb::addr_t, 3> args;
            
            if (m_needs_object_ptr) {
                args.push_back(object_ptr);
                if (m_objectivec)
                    args.push_back(cmd_ptr);
            }
            
            args.push_back(struct_address);
            
            lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallUserExpression (exe_ctx.GetThreadRef(), 
                                                                              wrapper_address, 
                                                                              args,
                                                                              options,
                                                                              shared_ptr_to_me));
            
            if (!call_plan_sp || !call_plan_sp->ValidatePlan (&error_stream))
                return eExecutionSetupError;
            
            lldb::addr_t function_stack_pointer = static_cast<ThreadPlanCallFunction *>(call_plan_sp.get())->GetFunctionStackPointer();

            function_stack_bottom = function_stack_pointer - Host::GetPageSize();
            function_stack_top = function_stack_pointer;
            
            if (log)
                log->Printf("-- [ClangUserExpression::Execute] Execution of expression begins --");
            
            if (exe_ctx.GetProcessPtr())
                exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
                
            ExecutionResults execution_result = exe_ctx.GetProcessRef().RunThreadPlan (exe_ctx, 
                                                                                       call_plan_sp,
                                                                                       options,
                                                                                       error_stream);
            
            if (exe_ctx.GetProcessPtr())
                exe_ctx.GetProcessPtr()->SetRunningUserExpression(false);
                
            if (log)
                log->Printf("-- [ClangUserExpression::Execute] Execution of expression completed --");

            if (execution_result == eExecutionInterrupted || execution_result == eExecutionHitBreakpoint)
            {
                const char *error_desc = NULL;
                
                if (call_plan_sp)
                {
                    lldb::StopInfoSP real_stop_info_sp = call_plan_sp->GetRealStopInfo();
                    if (real_stop_info_sp)
                        error_desc = real_stop_info_sp->GetDescription();
                }
                if (error_desc)
                    error_stream.Printf ("Execution was interrupted, reason: %s.", error_desc);
                else
                    error_stream.PutCString ("Execution was interrupted.");
                    
                if ((execution_result == eExecutionInterrupted && options.DoesUnwindOnError())
                    || (execution_result == eExecutionHitBreakpoint && options.DoesIgnoreBreakpoints()))
                    error_stream.PutCString ("\nThe process has been returned to the state before expression evaluation.");
                else
                    error_stream.PutCString ("\nThe process has been left at the point where it was interrupted, use \"thread return -x\" to return to the state before expression evaluation.");

                return execution_result;
            }
            else if (execution_result == eExecutionStoppedForDebug)
            {
                    error_stream.PutCString ("Execution was halted at the first instruction of the expression function because \"debug\" was requested.\n"
                                             "Use \"thread return -x\" to return to the state before expression evaluation.");
                    return execution_result;
            }
            else if (execution_result != eExecutionCompleted)
            {
                error_stream.Printf ("Couldn't execute function; result was %s\n", Process::ExecutionResultAsCString (execution_result));
                return execution_result;
            }
        }
        
        if  (FinalizeJITExecution (error_stream, exe_ctx, result, function_stack_bottom, function_stack_top))
        {
            return eExecutionCompleted;
        }
        else
        {
            return eExecutionSetupError;
        }
    }
    else
    {
        error_stream.Printf("Expression can't be run, because there is no JIT compiled function");
        return eExecutionSetupError;
    }
}

ExecutionResults
ClangUserExpression::Evaluate (ExecutionContext &exe_ctx,
                               const EvaluateExpressionOptions& options,
                               const char *expr_cstr,
                               const char *expr_prefix,
                               lldb::ValueObjectSP &result_valobj_sp,
                               Error &error)
{
    Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));

    lldb_private::ExecutionPolicy execution_policy = options.GetExecutionPolicy();
    const lldb::LanguageType language = options.GetLanguage();
    const ResultType desired_type = options.DoesCoerceToId() ? ClangUserExpression::eResultTypeId : ClangUserExpression::eResultTypeAny;
    ExecutionResults execution_results = eExecutionSetupError;
    
    Process *process = exe_ctx.GetProcessPtr();

    if (process == NULL || process->GetState() != lldb::eStateStopped)
    {
        if (execution_policy == eExecutionPolicyAlways)
        {
            if (log)
                log->Printf("== [ClangUserExpression::Evaluate] Expression may not run, but is not constant ==");
            
            error.SetErrorString ("expression needed to run but couldn't");
            
            return execution_results;
        }
    }
    
    if (process == NULL || !process->CanJIT())
        execution_policy = eExecutionPolicyNever;
    
    ClangUserExpressionSP user_expression_sp (new ClangUserExpression (expr_cstr, expr_prefix, language, desired_type));

    StreamString error_stream;
        
    if (log)
        log->Printf("== [ClangUserExpression::Evaluate] Parsing expression %s ==", expr_cstr);
    
    const bool keep_expression_in_memory = true;
    
    if (!user_expression_sp->Parse (error_stream, exe_ctx, execution_policy, keep_expression_in_memory))
    {
        if (error_stream.GetString().empty())
            error.SetErrorString ("expression failed to parse, unknown error");
        else
            error.SetErrorString (error_stream.GetString().c_str());
    }
    else
    {
        lldb::ClangExpressionVariableSP expr_result;

        if (execution_policy == eExecutionPolicyNever &&
            !user_expression_sp->CanInterpret())
        {
            if (log)
                log->Printf("== [ClangUserExpression::Evaluate] Expression may not run, but is not constant ==");
            
            if (error_stream.GetString().empty())
                error.SetErrorString ("expression needed to run but couldn't");
        }
        else
        {    
            error_stream.GetString().clear();
            
            if (log)
                log->Printf("== [ClangUserExpression::Evaluate] Executing expression ==");

            execution_results = user_expression_sp->Execute (error_stream, 
                                                             exe_ctx,
                                                             options,
                                                             user_expression_sp,
                                                             expr_result);
            
            if (execution_results != eExecutionCompleted)
            {
                if (log)
                    log->Printf("== [ClangUserExpression::Evaluate] Execution completed abnormally ==");
                
                if (error_stream.GetString().empty())
                    error.SetErrorString ("expression failed to execute, unknown error");
                else
                    error.SetErrorString (error_stream.GetString().c_str());
            }
            else 
            {
                if (expr_result)
                {
                    result_valobj_sp = expr_result->GetValueObject();
                    
                    if (log)
                        log->Printf("== [ClangUserExpression::Evaluate] Execution completed normally with result %s ==", result_valobj_sp->GetValueAsCString());
                }
                else
                {
                    if (log)
                        log->Printf("== [ClangUserExpression::Evaluate] Execution completed normally with no result ==");
                    
                    error.SetError(ClangUserExpression::kNoResult, lldb::eErrorTypeGeneric);
                }
            }
        }
    }
    
    if (result_valobj_sp.get() == NULL)
    {
        result_valobj_sp = ValueObjectConstResult::Create (exe_ctx.GetBestExecutionContextScope(), error);
    }

    return execution_results;
}