Sun Studio 12: Debugging a Program With dbx

Viewing Variables, Members, Types, and Classes

The whatis command prints the declarations or definitions of identifiers, structs, types and C++ classes, or the type of an expression. The identifiers you can look up include variables, functions, fields, arrays, and enumeration constants.

For more information, see whatis Command.

Looking Up Definitions of Variables, Members, and Functions

To print out the declaration of an identifier, type:

(dbx) whatis identifier

Qualify the identifier name with file and function information as needed.

For C++ programs, whatis identifier lists function template instantiations. Template definitions are displayed with whatis -t identifier. See Looking Up Definitions of Types and Classes.

For Java programs, whatis identifier, lists the declaration of a class, a method in the current class, a local variable in the current frame, or a field in the current class.

To print out the member function, type

(dbx) whatis block::draw
void block::draw(unsigned long pw);
(dbx) whatis table::draw
void table::draw(unsigned long pw);
(dbx) whatis block::pos
class point *block::pos();
(dbx) whatis table::pos
class point *block::pos();

To print out the data member, type:

(dbx) whatis block::movable
int movable;

On a variable, the whatis command tells you the variable”s type

(dbx) whatis the_table
class table *the_table;

On a field, the whatis command gives the field”s type.

(dbx) whatis the_table->draw
void table::draw(unsigned long pw);

When you are stopped in a member function, you can look up the this pointer.

(dbx) stop in brick::draw
(dbx) cont
(dbx) where 1
brick::draw(this = 0x48870, pw = 374752), line 124 in
(dbx) whatis this
class brick *this;

Looking Up Definitions of Types and Classes

The -t option of the whatis command displays the definition of a type. For C++, the list displayed by whatis -t includes template definitions and class template instantiations.

To print the declaration of a type or C++ class, type:

(dbx) whatis -t type_or_class_name

To see inherited members, the whatis command takes an -r option (for recursive) that displays the declaration of a specified class together with the members it inherits from base classes.

(dbx) whatis -t -r  class_name

The output from a whatis -r query may be long, depending on the class hierarchy and the size of the classes. The output begins with the list of members inherited from the most ancestral class. The inserted comment lines separate the list of members into their respective parent classes.

Here are two examples, using the class table, a child class of the parent class load_bearing_block, which is, in turn, a child class of block.

Without -r, whatis reports the members declared in class table:

(dbx) whatis -t class table
class table : public load_bearing_block {
    table::table(char *name, int w, int h, const class point &pos);
    virtual char *table::type();
    virtual void table::draw(unsigned long pw);

Here are results when whatis -r is used on a child class to see members it inherits:

(dbx) whatis -t -r class table
class table : public load_bearing_block {
  /* from base class table::load_bearing_block::block */
  block::block(char *name, int w, int h, const class point &pos, class load_bearing_block *blk);
    virtual char *block::type();
    char *block::name();
    int block::is_movable();
//  deleted several members from example protected:
    char *nm;
    int movable;
    int width;
    int height;
    class point  position;
    class load_bearing_block *supported_by;
    Panel_item panel_item;
    /* from base class table::load_bearing_block */
    load_bearing_block::load_bearing_block(char *name, int w, int h,
        const class point &pos, class load_bearing_block *blk);
    virtual int load_bearing_block::is_load_bearing();
    virtual class list *load_bearing_block::supported_blocks();
    void load_bearing_block::add_supported_block(class block &b);
    void load_bearing_block::remove_supported_block(class block &b);
    virtual void load_bearing_block::print_supported_blocks();
    virtual void load_bearing_block::clear_top();
    virtual void load_bearing_block::put_on(class block &object);
    class point load_bearing_block::get_space(class block &object);
    class point load_bearing_block::find_space(class block &object);
    class point load_bearing_block::make_space(class block &object);
    class list *support_for;
    /* from class table */
    table::table(char *name, int w, int h, const class point &pos);
    virtual char *table::type();
    virtual void table::draw(unsigned long pw);