llvm-project/lldb/source/Plugins/Language/CPlusPlus/BlockPointer.cpp

//===-- BlockPointer.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
// C++ Includes
// Other libraries and framework includes
// Project includes
#include "BlockPointer.h"

#include "lldb/Core/ValueObject.h"
#include "lldb/DataFormatters/FormattersHelpers.h"
#include "lldb/Symbol/ClangASTContext.h"
#include "lldb/Symbol/ClangASTImporter.h"
#include "lldb/Symbol/CompilerType.h"
#include "lldb/Symbol/TypeSystem.h"
#include "lldb/Target/Target.h"

#include "lldb/Utility/LLDBAssert.h"

using namespace lldb;
using namespace lldb_private;
using namespace lldb_private::formatters;

namespace lldb_private
{
namespace formatters
{

class BlockPointerSyntheticFrontEnd : public SyntheticChildrenFrontEnd
{
public:
    BlockPointerSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
        : SyntheticChildrenFrontEnd(*valobj_sp),
          m_block_struct_type()
    {
        CompilerType block_pointer_type(m_backend.GetCompilerType());
        CompilerType function_pointer_type;
        block_pointer_type.IsBlockPointerType(&function_pointer_type);
        
        TargetSP target_sp(m_backend.GetTargetSP());
        
        if (!target_sp)
        {
            return;
        }
        
        Error err;
        TypeSystem *type_system = target_sp->GetScratchTypeSystemForLanguage(&err, lldb::eLanguageTypeC_plus_plus);
        
        if (!err.Success() || !type_system)
        {
            return;
        }
        
        ClangASTContext *clang_ast_context = llvm::dyn_cast<ClangASTContext>(type_system);
        
        if (!clang_ast_context)
        {
            return;
        }
        
        ClangASTImporterSP clang_ast_importer = target_sp->GetClangASTImporter();
        
        if (!clang_ast_importer)
        {
            return;
        }
        
        const char *const   isa_name("__isa");
        const CompilerType  isa_type = clang_ast_context->GetBasicType(lldb::eBasicTypeObjCClass);
        const char *const   flags_name("__flags");
        const CompilerType  flags_type = clang_ast_context->GetBasicType(lldb::eBasicTypeInt);
        const char *const   reserved_name("__reserved");
        const CompilerType  reserved_type = clang_ast_context->GetBasicType(lldb::eBasicTypeInt);
        const char *const   FuncPtr_name("__FuncPtr");
        const CompilerType  FuncPtr_type = clang_ast_importer->CopyType(*clang_ast_context, function_pointer_type);
        
        m_block_struct_type = clang_ast_context->CreateStructForIdentifier(ConstString(),
                                                                           {
                                                                               {isa_name, isa_type},
                                                                               {flags_name, flags_type},
                                                                               {reserved_name, reserved_type},
                                                                               {FuncPtr_name, FuncPtr_type}
                                                                           });

    }

    ~BlockPointerSyntheticFrontEnd() override = default;

    size_t
    CalculateNumChildren() override
    {
        const bool omit_empty_base_classes = false;
        return m_block_struct_type.GetNumChildren(omit_empty_base_classes);
    }

    lldb::ValueObjectSP
    GetChildAtIndex(size_t idx) override
    {
        if (!m_block_struct_type.IsValid())
        {
            return lldb::ValueObjectSP();
        }
        
        if (idx >= CalculateNumChildren())
        {
            return lldb::ValueObjectSP();
        }
        
        const bool thread_and_frame_only_if_stopped = true;
        ExecutionContext exe_ctx = m_backend.GetExecutionContextRef().Lock(thread_and_frame_only_if_stopped);
        const bool transparent_pointers = false;
        const bool omit_empty_base_classes = false;
        const bool ignore_array_bounds = false;
        ValueObject *value_object = nullptr;
    
        std::string child_name;
        uint32_t child_byte_size = 0;
        int32_t child_byte_offset = 0;
        uint32_t child_bitfield_bit_size = 0;
        uint32_t child_bitfield_bit_offset = 0;
        bool child_is_base_class = false;
        bool child_is_deref_of_parent = false;
        uint64_t language_flags = 0;
        
        const CompilerType child_type = m_block_struct_type.GetChildCompilerTypeAtIndex(&exe_ctx, idx, transparent_pointers, omit_empty_base_classes, ignore_array_bounds, child_name, child_byte_size, child_byte_offset, child_bitfield_bit_size, child_bitfield_bit_offset, child_is_base_class, child_is_deref_of_parent, value_object, language_flags);
        
        ValueObjectSP struct_pointer_sp = m_backend.Cast(m_block_struct_type.GetPointerType());
        
        if (!struct_pointer_sp)
        {
            return lldb::ValueObjectSP();
        }
        
        Error err;
        ValueObjectSP struct_sp = struct_pointer_sp->Dereference(err);
        
        if (!struct_sp || !err.Success())
        {
            return lldb::ValueObjectSP();
        }
        
        ValueObjectSP child_sp(struct_sp->GetSyntheticChildAtOffset(child_byte_offset,
                                                                    child_type,
                                                                    true,
                                                                    ConstString(child_name.c_str(), child_name.size())));

        return child_sp;
    }

    // return true if this object is now safe to use forever without
    // ever updating again; the typical (and tested) answer here is
    // 'false'
    bool
    Update() override
    {
        return false;
    }

    // maybe return false if the block pointer is, say, null
    bool
    MightHaveChildren() override
    {
        return true;
    }

    size_t
    GetIndexOfChildWithName(const ConstString &name) override
    {
        if (!m_block_struct_type.IsValid())
            return UINT32_MAX;
        
        const bool omit_empty_base_classes = false;
        return m_block_struct_type.GetIndexOfChildWithName(name.AsCString(), omit_empty_base_classes);
    }

private:
    CompilerType m_block_struct_type;
};

} // namespace formatters
} // namespace lldb_private

bool
lldb_private::formatters::BlockPointerSummaryProvider(ValueObject &valobj, Stream &s, const TypeSummaryOptions &)
{
    lldb_private::SyntheticChildrenFrontEnd *synthetic_children = BlockPointerSyntheticFrontEndCreator(nullptr, valobj.GetSP());
    if (!synthetic_children)
    {
        return false;
    }

    synthetic_children->Update();

    static const ConstString s_FuncPtr_name("__FuncPtr");
    
    lldb::ValueObjectSP child_sp = synthetic_children->GetChildAtIndex(synthetic_children->GetIndexOfChildWithName(s_FuncPtr_name));
    
    if (!child_sp)
    {
        return false;
    }
    
    lldb::ValueObjectSP qualified_child_representation_sp = child_sp->GetQualifiedRepresentationIfAvailable(lldb::eDynamicDontRunTarget, true);

    const char *child_value = qualified_child_representation_sp->GetValueAsCString();

    s.Printf("%s", child_value);

    return true;
}

lldb_private::SyntheticChildrenFrontEnd *
lldb_private::formatters::BlockPointerSyntheticFrontEndCreator(CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp)
{
    if (!valobj_sp)
        return nullptr;
    return new BlockPointerSyntheticFrontEnd(valobj_sp);
}