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gdb: C Plus Plus Expressions

 
 15.4.1.3 C++ Expressions
 ........................
 
 GDB expression handling can interpret most C++ expressions.
 
      _Warning:_ GDB can only debug C++ code if you use the proper
      compiler and the proper debug format.  Currently, GDB works best
      when debugging C++ code that is compiled with the most recent
      version of GCC possible.  The DWARF debugging format is preferred;
      GCC defaults to this on most popular platforms.  Other compilers
      and/or debug formats are likely to work badly or not at all when
      using GDB to debug C++ code.  Compilation.
 
   1. Member function calls are allowed; you can use expressions like
 
           count = aml->GetOriginal(x, y)
 
   2. While a member function is active (in the selected stack frame),
      your expressions have the same namespace available as the member
      function; that is, GDB allows implicit references to the class
      instance pointer 'this' following the same rules as C++.  'using'
      declarations in the current scope are also respected by GDB.
 
   3. You can call overloaded functions; GDB resolves the function call
      to the right definition, with some restrictions.  GDB does not
      perform overload resolution involving user-defined type
      conversions, calls to constructors, or instantiations of templates
      that do not exist in the program.  It also cannot handle ellipsis
      argument lists or default arguments.
 
      It does perform integral conversions and promotions, floating-point
      promotions, arithmetic conversions, pointer conversions,
      conversions of class objects to base classes, and standard
      conversions such as those of functions or arrays to pointers; it
      requires an exact match on the number of function arguments.
 
      Overload resolution is always performed, unless you have specified
      'set overload-resolution off'.  GDB Features for C++
      Debugging C Plus Plus.
 
      You must specify 'set overload-resolution off' in order to use an
      explicit function signature to call an overloaded function, as in
           p 'foo(char,int)'('x', 13)
 
      The GDB command-completion facility can simplify this; see 
      Command Completion Completion.
 
   4. GDB understands variables declared as C++ lvalue or rvalue
      references; you can use them in expressions just as you do in C++
      source--they are automatically dereferenced.
 
      In the parameter list shown when GDB displays a frame, the values
      of reference variables are not displayed (unlike other variables);
      this avoids clutter, since references are often used for large
      structures.  The _address_ of a reference variable is always shown,
      unless you have specified 'set print address off'.
 
   5. GDB supports the C++ name resolution operator '::'--your
      expressions can use it just as expressions in your program do.
      Since one scope may be defined in another, you can use '::'
      repeatedly if necessary, for example in an expression like
      'SCOPE1::SCOPE2::NAME'.  GDB also allows resolving name scope by
      reference to source files, in both C and C++ debugging (
      Program Variables Variables.).
 
   6. GDB performs argument-dependent lookup, following the C++
      specification.
 

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