ACE_ODB(3)

NAME

ACE_ODB - This is the object database (ODB) that keeps track of all live ACE objects.

SYNOPSIS

#include <ace/Dump.h>
class ACE_ODB
{
  public:
    enum {MAX_TABLE_SIZE = 100000};
    void dump_objects (void);
    void register_object (const ACE_Dumpable *dumper);
    void remove_object (const void *this_);
    static ACE_ODB *instance (void);
  private:
    ACE_ODB (void);
    struct Tuple
    {
      public:
        const void *this_;
        const ACE_Dumpable_Ptr dumper_;
        inline Tuple (void);
    };

static ACE_ODB *instance_; Tuple object_table_[ACE_ODB::MAX_TABLE_SIZE]; int current_size_; };

DESCRIPTION

A prototype mechanism that allow all ACE objects to be registered with a central in-memory "database" that can dump the state of all live ACE objects (e.g., from within a debugger).

To turn on this feature simply compile with -DACE_NDEBUG

There are several interesting aspects to this design:

1. It uses the External Polymorphism pattern to avoid having to
derive all ACE classes from a common base class that has virtual
methods (this is crucial to avoid unnecessary overhead). In
addition, there is no additional space added to ACE objects
(this is crucial to maintain binary layout compatibility).

2. This mechanism can be conditionally compiled in order to
completely disable this feature entirely. Moreover, by
using macros there are relatively few changes to ACE code.

3. This mechanism copes with single-inheritance hierarchies of
dumpable classes. In such cases we typically want only one
dump, corresponding to the most derived instance. Thanks to
Christian Millour ([email protected]) for illustrating how to do
this. Note, however, that this scheme doesn't generalize to
work with multiple-inheritance or virtual base classes.

Future work includes:

1. Using a dynamic object table rather than a static table

2. Adding support to allow particular classes of objects to
be selectively dumped.

PUBLIC MEMBERS

void dump_objects (void);

void register_object (const ACE_Dumpable *dumper);

void remove_object (const void *this_);

static ACE_ODB *instance (void);

PRIVATE MEMBERS

ACE_ODB (void);

static ACE_ODB *instance_;

Tuple object_table_[ACE_ODB::MAX_TABLE_SIZE];

int current_size_;

AUTHOR

Doug Schmidt

LIBRARY

ace