source: src/Common/PassVisitor.proto.h@ e1c1829

#pragma once

typedef std::function<void( void * )> cleanup_func_t;

class guard_value_impl {
public:
        guard_value_impl() = default;

        ~guard_value_impl() {
                while( !cleanups.empty() ) {
                        auto& cleanup = cleanups.top();
                        cleanup.func( cleanup.val );
                        cleanups.pop();
                }
        }

        void push( cleanup_func_t && func, void* val ) {
                cleanups.emplace( std::move(func), val );
        }

private:
        struct cleanup_t {
                cleanup_func_t func;
                void * val;

                cleanup_t( cleanup_func_t&& func, void * val ) : func(func), val(val) {}
        };

        std::stack< cleanup_t > cleanups;
};

typedef std::function< void( cleanup_func_t, void * ) > at_cleanup_t;

//-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
// Deep magic (a.k.a template meta programming) to make the templated visitor work
// Basically the goal is to make 2 previsit_impl
// 1 - Use when a pass implements a valid previsit. This uses overloading which means the any overload of 
//     'pass.previsit( node )' that compiles will be used for that node for that type
//     This requires that this option only compile for passes that actually define an appropriate visit.
//     SFINAE will make sure the compilation errors in this function don't halt the build.
//     See http://en.cppreference.com/w/cpp/language/sfinae for details on SFINAE
// 2 - Since the first implementation might not be specilizable, the second implementation exists and does nothing.
//     This is needed only to eliminate the need for passes to specify any kind of handlers.
//     The second implementation only works because it has a lower priority. This is due to the bogus last parameter.
//     The second implementation takes a long while the first takes an int. Since the caller always passes an literal 0
//     the first implementation takes priority in regards to overloading.
// Mutator functions work along the same principal
//-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
// Visit
template<typename pass_type, typename node_type>
static inline auto previsit_impl( pass_type& pass, node_type * node, __attribute__((unused)) int unused ) -> decltype( pass.previsit( node ), void() ) {
        pass.previsit( node );
}

template<typename pass_type, typename node_type>
static inline void previsit_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) node_type * node, __attribute__((unused)) long unused ) {}


template<typename pass_type, typename node_type>
static inline auto postvisit_impl( pass_type& pass, node_type * node, __attribute__((unused)) int unused ) -> decltype( pass.postvisit( node ), void() ) {
        pass.postvisit( node );
}

template<typename pass_type, typename node_type>
static inline void postvisit_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) node_type * node, __attribute__((unused)) long unused ) {}

// Mutate
template<typename pass_type, typename node_type>
static inline auto premutate_impl( pass_type& pass, node_type * node, __attribute__((unused)) int unused ) -> decltype( pass.premutate( node ), void() ) {
        return pass.premutate( node );
}

template<typename pass_type, typename node_type>
static inline void premutate_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) node_type * node, __attribute__((unused)) long unused ) {}


template<typename return_type, typename pass_type, typename node_type>
static inline auto postmutate_impl( pass_type& pass, node_type * node, __attribute__((unused)) int unused ) -> decltype( pass.postmutate( node ) ) {
        return pass.postmutate( node );
}

template<typename return_type, typename pass_type, typename node_type>
static inline return_type postmutate_impl( __attribute__((unused)) pass_type& pass, node_type * node, __attribute__((unused)) long unused ) { return node; }

// Begin/End scope
template<typename pass_type>
static inline auto begin_scope_impl( pass_type& pass, __attribute__((unused)) int unused ) -> decltype( pass.beginScope(), void() ) {
        pass.beginScope();
}

template<typename pass_type>
static inline void begin_scope_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) long unused ) {}


template<typename pass_type>
static inline auto end_scope_impl( pass_type& pass, __attribute__((unused)) int unused ) -> decltype( pass.endScope(), void() ) {
        pass.endScope();
}

template<typename pass_type>
static inline void end_scope_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) long unused ) {}

// Fields
#define FIELD_PTR( type, name )                                                                                                        \
template<typename pass_type>                                                                                                           \
static inline auto name##_impl( pass_type& pass, __attribute__((unused)) int unused ) -> decltype( &pass.name ) { return &pass.name; } \
                                                                                                                                       \
template<typename pass_type>                                                                                                           \
static inline type * name##_impl( __attribute__((unused)) pass_type& pass, __attribute__((unused)) long unused ) { return nullptr;}    \

FIELD_PTR( TypeSubstitution *, env )
FIELD_PTR( std::list< Statement* >, stmtsToAddBefore )
FIELD_PTR( std::list< Statement* >, stmtsToAddAfter  )
FIELD_PTR( bool, skip_children )
FIELD_PTR( at_cleanup_t, at_cleanup )