lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h

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

#ifndef liblldb_ClangFunctionCaller_h_
#define liblldb_ClangFunctionCaller_h_

// C Includes
// C++ Includes
// Other libraries and framework includes
// Project includes
#include "ClangExpressionHelper.h"

#include "lldb/Core/ClangForward.h"
#include "lldb/Core/Address.h"
#include "lldb/Core/ArchSpec.h"
#include "lldb/Core/Value.h"
#include "lldb/Core/ValueObjectList.h"
#include "lldb/Expression/FunctionCaller.h"
#include "lldb/Symbol/CompilerType.h"
#include "lldb/Target/Process.h"

namespace lldb_private
{
    
class ASTStructExtractor;
class ClangExpressionParser;

//----------------------------------------------------------------------
/// @class ClangFunctionCaller ClangFunctionCaller.h "lldb/Expression/ClangFunctionCaller.h"
/// @brief Encapsulates a function that can be called.
///
/// A given ClangFunctionCaller object can handle a single function signature.
/// Once constructed, it can set up any number of concurrent calls to
/// functions with that signature.
///
/// It performs the call by synthesizing a structure that contains the pointer
/// to the function and the arguments that should be passed to that function,
/// and producing a special-purpose JIT-compiled function that accepts a void*
/// pointing to this struct as its only argument and calls the function in the 
/// struct with the written arguments.  This method lets Clang handle the
/// vagaries of function calling conventions.
///
/// The simplest use of the ClangFunctionCaller is to construct it with a
/// function representative of the signature you want to use, then call
/// ExecuteFunction(ExecutionContext &, Stream &, Value &).
///
/// If you need to reuse the arguments for several calls, you can call
/// InsertFunction() followed by WriteFunctionArguments(), which will return
/// the location of the args struct for the wrapper function in args_addr_ref.
///
/// If you need to call the function on the thread plan stack, you can also 
/// call InsertFunction() followed by GetThreadPlanToCallFunction().
///
/// Any of the methods that take arg_addr_ptr or arg_addr_ref can be passed
/// a pointer set to LLDB_INVALID_ADDRESS and new structure will be allocated
/// and its address returned in that variable.
/// 
/// Any of the methods that take arg_addr_ptr can be passed NULL, and the
/// argument space will be managed for you.
//----------------------------------------------------------------------    
class ClangFunctionCaller : public FunctionCaller
{
    friend class ASTStructExtractor;
    
    class ClangFunctionCallerHelper : public ClangExpressionHelper
    {
    public:
        ClangFunctionCallerHelper (ClangFunctionCaller &owner) :
            m_owner(owner)
        {
        }
        
        ~ClangFunctionCallerHelper() override = default;
        
        //------------------------------------------------------------------
        /// Return the object that the parser should use when resolving external
        /// values.  May be NULL if everything should be self-contained.
        //------------------------------------------------------------------
        ClangExpressionDeclMap *
        DeclMap() override
        {
            return NULL;
        }
        
        //------------------------------------------------------------------
        /// Return the object that the parser should allow to access ASTs.
        /// May be NULL if the ASTs do not need to be transformed.
        ///
        /// @param[in] passthrough
        ///     The ASTConsumer that the returned transformer should send
        ///     the ASTs to after transformation.
        //------------------------------------------------------------------
        clang::ASTConsumer *
        ASTTransformer(clang::ASTConsumer *passthrough) override;

    private:
        ClangFunctionCaller                      &m_owner;
        std::unique_ptr<ASTStructExtractor> m_struct_extractor;         ///< The class that generates the argument struct layout.
    };

public:
    //------------------------------------------------------------------
    /// Constructor
    ///
    /// @param[in] exe_scope
    ///     An execution context scope that gets us at least a target and 
    ///     process.
    ///
    /// @param[in] ast_context
    ///     The AST context to evaluate argument types in.
    ///
    /// @param[in] return_qualtype
    ///     An opaque Clang QualType for the function result.  Should be
    ///     defined in ast_context.
    ///
    /// @param[in] function_address
    ///     The address of the function to call.
    ///
    /// @param[in] arg_value_list
    ///     The default values to use when calling this function.  Can
    ///     be overridden using WriteFunctionArguments().
    //------------------------------------------------------------------
    ClangFunctionCaller (ExecutionContextScope &exe_scope,
                         const CompilerType &return_type,
                         const Address& function_address,
                         const ValueList &arg_value_list,
                         const char *name);
    
    ~ClangFunctionCaller() override;

    //------------------------------------------------------------------
    /// Compile the wrapper function
    ///
    /// @param[in] errors
    ///     The stream to print parser errors to.
    ///
    /// @return
    ///     The number of errors.
    //------------------------------------------------------------------
    unsigned
    CompileFunction (Stream &errors) override;
    
    ExpressionTypeSystemHelper *
    GetTypeSystemHelper () override
    {
        return &m_type_system_helper;
    }

protected:
    const char *GetWrapperStructName()
    {
        return m_wrapper_struct_name.c_str();
    }

private:
    //------------------------------------------------------------------
    // For ClangFunctionCaller only
    //------------------------------------------------------------------

    // Note: the parser needs to be destructed before the execution unit, so
    // declare the execution unit first.
    ClangFunctionCallerHelper   m_type_system_helper;
};

} // namespace lldb_private

#endif // liblldb_ClangFunctionCaller_h_