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OpenVMS Debugger Manual
C.7.2 Constructs in Language and Address Expressions
Supported constructs in language and address expressions for C++ follow:
| Symbol |
Construct |
|
[ ]
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Subscripting
|
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. (period)
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Structure component selection
|
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->
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Pointer dereferencing
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::
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Scope resolution
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C.7.3 Data Types
Supported C++ data types follow:
| C++ Data Type |
Operating System Data Type Name |
|
__int64 (Alpha and Integrity servers)
|
Quadword Integer (Q)
|
|
unsigned __int64 (Alpha and Integrity servers)
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Quadword Unsigned (QU)
|
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__int32 (Alpha and Integrity servers)
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Longword Integer (L)
|
|
unsigned __int32 (Alpha and Integrity servers)
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Longword Unsigned (LU)
|
|
int
|
Longword Integer (L)
|
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unsigned int
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Longword Unsigned (LU)
|
|
__int16 (Alpha and Integrity servers)
|
Word Integer (W)
|
|
unsigned __int16 (Alpha and Integrity servers)
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Word Unsigned (WU)
|
|
short int
|
Word Integer (W)
|
|
unsigned short int
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Word Unsigned (WU)
|
|
char
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Byte Integer (B)
|
|
unsigned char
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Byte Unsigned (BU)
|
|
float
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F_Floating (F)
|
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__f_float (Alpha and Integrity servers)
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F_Floating (F)
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double
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D_Floating (D)
|
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double
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G_Floating (G)
|
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__g_float (Alpha and Integrity servers)
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G_Floating (G)
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float (Alpha and Integrity servers)
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IEEE S_Floating (FS)
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__s_float (Alpha and Integrity servers)
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IEEE S_Floating (FS)
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double (Alpha and Integrity servers)
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IEEE T_Floating (FT)
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__t_float (Alpha and Integrity servers)
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IEEE T_Floating (FT)
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enum
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(None)
|
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struct
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(None)
|
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class
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(None)
|
|
union
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(None)
|
|
Pointer Type
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(None)
|
|
Array Type
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(None)
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Floating-point numbers of type float may be represented by F_Floating
or IEEE S_Floating, depending on compiler switches.
Floating-point numbers of type double may be represented by IEEE
T_Floating, D_Floating, or G_Floating, depending on compiler switches.
C.7.4 Case Sensitivity
Symbol names are case sensitive in C++. This means that uppercase and
lowercase letters are treated as different characters.
C.7.5 Displaying Information About a Class
Use the command SHOW SYMBOL to display static information about a class
declaration. Use the command EXAMINE to view dynamic information about
class objects (see Section C.7.6).
The command SHOW SYMBOL/FULL displays the class type declaration,
including:
Data members (including static data members)
Member functions (including static member functions)
Constructors and destructors
Base classes and derived classes
For example:
dbg> SHOW SYMBOL /TYPE C
type C
struct (C, 13 components), size: 40 bytes
overloaded name C
instance C::C(void)
instance C::C(const C &)
dbg> SHOW SYMBOL /FULL C
type C
struct (C, 13 components), size: 40 bytes
inherits: B1, size: 24 bytes, offset: 0 bytes
B2, size: 24 bytes, offset: 12 bytes
contains the following members:
overloaded name C::g
instance C::g(int)
instance C::g(long)
instance C::g(char)
j : longword integer, size: 4 bytes, offset: 24 bytes
s : longword integer, size: 4 bytes, address: # [static]
overloaded name C
int ==(C &)
C & =(const C &)
void h(void) [virtual]
~C(void)
__vptr : typed pointer type, size: 4 bytes, offset: 4 bytes
__bptr : typed pointer type, size: 4 bytes, offset: 8 bytes
structure has been padded, size: 4 bytes, offset: 36 bytes
overloaded name C
instance C::C(void)
instance C::C(const C &)
DBG>
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Note that SHOW SYMBOL/FULL does not display members of base classes or
derived classes. Use the commands SHOW SYMBOL/FULL base_class_name and
SHOW SYMBOL/FULL derived_class_name to display information about
members of those classes. For example:
DBG> SHOW SYMBOL /FULL B1
type B1
struct (B1, 8 components), size: 24 bytes
inherits: virtual A
is inherited by: C
contains the following members:
i : longword integer, size: 4 bytes, offset: 0 bytes
overloaded name B1
void f(void)
B1 & =(const B1 &)
void h(void) [virtual]
__vptr : typed pointer type, size: 4 bytes, offset: 4 bytes
__bptr : typed pointer type, size: 4 bytes, offset: 8 bytes
structure has been padded, size: 12 bytes, offset: 12 bytes
overloaded name B1
instance B1::B1(void)
instance B1::B1(const B1 &)
DBG>
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Use the command SHOW SYMBOL/FULL class_member_name to display
information about class members. For example:
DBG> SHOW SYMBOL /FULL j
record component C::j
address: offset 24 bytes from beginning of record
atomic type, longword integer, size: 4 bytes
record component A::j
address: offset 4 bytes from beginning of record
atomic type, longword integer, size: 4 bytes
DBG>
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Use the SHOW SYMBOL/FULL command to display detailed information about
an object.
Note that SHOW SYMBOL does not currently support qualified names. For
example, the following commands are not currently supported:
SHOW SYMBOL object_name.function_name
SHOW SYMBOL class_name::member_name
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C.7.6 Displaying Information About an Object
The debugger uses C++ symbol lookup rules to display information about
objects. Use the command EXAMINE to display the current value of an
object. For example:
DBG> EXAMINE a
CXXDOCEXAMPLE\main\a: struct A
i: 0
j: 1
__vptr: 131168
DBG>
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You can also display individual object members using the member access
operators, period (.) and right arrow (->), with the EXAMINE
command. For example:
DBG> EXAMINE ptr
CXXDOCEXAMPLE\main\ptr: 40
DBG> EXAMINE *ptr
*CXXDOCEXAMPLE\main\ptr: struct A
i: 0
j: 1
__vptr: 131168
DBG> EXAMINE a.i
CXXDOCEXAMPLE\main\a.i: 0
DBG> EXAMINE ptr->i
CXXDOCEXAMPLE\main\ptr->i: 0
DBG>
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The debugger correctly interprets virtual inheritance. For example:
DBG> EXAMINE c
CXXDOCEXAMPLE\main\c: struct C
inherit B1
inherit virtual A
i: 8
j: 9
__vptr: 131200
i: 10
__vptr: 131232
__bptr: 131104
inherit B2
inherit virtual A (already printed, see above)
i: 11
__vptr: 131280
__bptr: 131152
j: 12
__vptr: 131232
__bptr: 131104
DBG>
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Use the scope resolution operator (::) to reference global variables,
to reference hidden members in base classes, to explicitly reference a
member that is inherited, or otherwise to name a member hidden by the
current context. For example:
DBG> EXAMINE c.j
CXXDOCEXAMPLE\main\c.j: 12
DBG> EXAMINE c.A::j
CXXDOCEXAMPLE\main\c.A::j: 9
DBG> EXAMINE x
CXXDOCEXAMPLE\main\x: 101
DBG> EXAMINE ::x
CXXDOCEXAMPLE\x: 13
DBG>
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To resolve ambiguous member references, the debugger lists the members
that satisfy the reference and requests an unambiguous reference to the
member. For example:
DBG> EXAMINE c.i
%DEBUG-I-AMBIGUOUS, 'i' is ambiguous, matching the following
CXXDOCEXAMPLE\main\c.B1::i
CXXDOCEXAMPLE\main\c.B2::i
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> EXAMINE c.B1::i
CXXDOCEXAMPLE\main\c.B1::i: 10
DBG>
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Use the scope resolution operator (::) to refer to static data members.
For example:
DBG> EXAMINE c.s
CXXDOCEXAMPLE\main\c.s: 42
DBG> EXAMINE C::s
C::s: 42
DBG>
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Use the SHOW SYMBOL/FULL to display the class type of an object (see
Section C.7.5).
C.7.7 Setting Watchpoints
You can set watchpoints on objects. All nonstatic data members are
watched (including those in base classes). Static data members are not
watched when you set a watchpoint on the object. However, you can
explicitly set watchpoints on static data members. For example:
DBG> SET WATCH c
%DEBUG-I-WPTTRACE, non-static watchpoint, tracing every instruction
DBG> GO
watch of CXXDOCEXAMPLE\main\c.i at CXXDOCEXAMPLE\main\%LINE 50+8
50: c.B2::i++;
old value: 11
new value: 12
break at CXXDOCEXAMPLE\main\%LINE 51
51: c.s++;
DBG> SET WATCH c.s
DBG> GO
watch of CXXDOCEXAMPLE\main\c.s at CXXDOCEXAMPLE\main\%LINE 51+16
51: c.s++;
old value: 43
new value: 44
break at CXXDOCEXAMPLE\main\%LINE 53
53: b1.f();
DBG>
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C.7.8 Debugging Functions
The debugger uses C++ symbol lookup rules to display information on
member functions. For example:
DBG> EXAMINE /SOURCE b1.f
module CXXDOCEXAMPLE
14: void f() {}
DBG> SET BREAK B1::f
DBG> GO
break at routine B1::f
14: void f() {}
DBG>
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The debugger correctly interprets references to the
this pointer. For example:
DBG> EXAMINE this
B1::f::this: 16
DBG> EXAMINE *this
*B1::f::this: struct B1
inherit virtual A
i: 2
j: 3
__vptr: 131184
i: 4
__vptr: 131248
__bptr: 131120
DBG> EXAMINE this->i
B1::f::this->i: 4
DBG> EXAMINE this->j
B1::f::this->A::j: 3
DBG>EXAMINE i
B1::f::this->i: 4
DBG> EXAMINE j
B1::f::this->A::j: 3
DBG>
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The debugger correctly references virtual member functions. For example:
DBG> EXAMINE /SOURCE %LINE 53
module CXXDOCEXAMPLE
53: b1.f();
DBG> SET BREAK this->h
DBG> SHOW BREAK
breakpoint at routine B1::f
breakpoint at routine B1::h
!!
!! We are at the call to B1::f made at 'c.B1::f()'.
!! Here this->h matches C::h.
!!
DBG> GO
break at routine B1::f
14: void f() {}
DBG> EXAMINE /SOURCE %LINE 54
module CXXDOCEXAMPLE
54: c.B1::f();
DBG> SET BREAK this->h
DBG> SHOW BREAK
breakpoint at routine B1::f
breakpoint at routine B1::h
breakpoint at routine C::h
!!
!! Handling overloaded functions
!!
DBG> show symbol/full g
overloaded name C::g
routine C::g(char)
type signature: void g(char)
address: 132224, size: 128 bytes
routine C::g(long)
type signature: void g(long)
address: 132480, size: 96 bytes
DBG> SET BREAK g
%DEBUG-I-NOTUNQOVR, symbol 'g' is overloaded
overloaded name C::g
instance C::g(int)
instance C::g(long)
instance C::g(char)
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> SET BREAK g(int)
DBG> CANCEL BREAK/ALL
DBG>
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If you try to set a break on an overloaded function, the debugger lists
the instances of the function and requests that you specify the correct
instance. For example, with Debugger Version 7.2:
DBG> SET BREAK g
%DEBUG-I-NOTUNQOVR, symbol 'g' is overloaded
overloaded name C::g
instance void g(int)
instance void g(long)
instance void g(char *)
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> SET BREAK g(int)
DBG>
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Note
The means of displaying and specifying overloaded functions is
different than in the OpenVMS Debugger Version 7.1C.
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The debugger provides support for debugging constructors, destructors,
and operators. For example:
DBG> SET BREAK C
%DEBUG-I-NOTUNQOVR, symbol 'C' is overloaded
overloaded name C
instance C::C(void)
instance C::C(const C &)
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> SHOW SYMBOL /FULL ~C
routine C::~C
type signature: ~C(void)
code address: #, size: 152 bytes
procedure descriptor address: #
DBG> SET BREAK ~C
DBG> SET BREAK %NAME'=='
%DEBUG-W-UNALLOCATED, '==' is not allocated in memory (optimized away)
%DEBUG-E-CMDFAILED, the SET BREAK command has failed
DBG> SHOW SYMBOL /FULL ==,
routine c::operator==, type
signature: bool operator==©
code address: 198716, size:
40 bytes, procedure descriptor
address: 65752
DBG> SET BREAK operator==
DBG> SHOW SYMBOL /FULL ==
routine C::==
type signature: int ==(C &)
address: unallocated
DBG> SHOW BREAK
breakpoint at routine C::~C
DBG>
DBG> examine C::~C
C::~C: alloc r35 = ar.pfs, 3F, 01, 00
DBG>
DBG> ex/source ~C
module CXXDOCEXAMPLE
37: ~C() {}
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C.7.9 Limitations on Debugger Support for C++
The following limitations apply when you debug a C++ program:
- You cannot specify a template by name in a debugger command. You
must use the name of the instantiation of the template.
- In C++, expressions in the instantiated template name can be full
constant expressions, such as stack<double,f*10>. This form is
not yet supported in the debugger; you must enter the value of the
expression (for example, if f is 10 in the stack example, you must
enter 100).
Example C-1 contains CXXDOCEXAMPLE.C, a C++ example program.
| Example C-1 C++ Example Program
CXXDOCEXAMPLE.C |
int x = 0;
struct A
{
int i,j;
void f() {}
virtual void h() {};
A() { i=x++; j=x++; }
};
struct B1 : virtual A
{
int i;
void f() {}
virtual void h() {}
B1() { i=x++; }
};
struct B2 : virtual A
{
int i;
void f() {}
virtual void h() {}
B2() { i=x++; }
};
struct C : B1, B2
{
int j;
static int s;
void g( int ) {}
void g( long ) {}
void g( char ) {}
void h() {}
operator ==( C& ) { return 0; }
C() { j=x++; }
~C() {}
};
int C::s = 42;
main()
{
A a; B1 b1; B2 b2; C c;
A *ptr = &a;
int x = 101;
x++;
c.s++;
c.B2::i++;
c.s++;
b1.f();
c.B1::f();
c.g(1);
c.g( (long) 1 );
c.g( 'a' );
}
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Example C-2 contains a sample debugging session of the program
contained in Example C-1.
| Example C-2 C++ Debugging Example |
DBG> GO
break at routine CXXDOCEXAMPLE\main
44: A a; B1 b1; B2 b2; C c;
DBG> STEP
stepped to CXXDOCEXAMPLE\main\%LINE 45
45: A *ptr = &a;
DBG> STEP
stepped to CXXDOCEXAMPLE\main\%LINE 46
46: int x = 101;
DBG> STEP
stepped to CXXDOCEXAMPLE\main\%LINE 47
47: x++;
!!
!! Displaying class information
!!
DBG> SHOW SYMBOL /TYPE C
type C
struct (C, 13 components), size: 40 bytes
overloaded name C
instance C::C(void)
instance C::C(const C &)
DBG> SHOW SYMBOL /FULL C
type C
struct (C, 13 components), size: 40 bytes
inherits: B1, size: 24 bytes, offset: 0 bytes
B2, size: 24 bytes, offset: 12 bytes
contains the following members:
overloaded name C::g
instance C::g(int)
instance C::g(long)
instance C::g(char)
j : longword integer, size: 4 bytes, offset: 24 bytes
s : longword integer, size: 4 bytes, address: # [static]
overloaded name C
int ==(C &)
C & =(const C &)
void h(void) [virtual]
~C(void)
__vptr : typed pointer type, size: 4 bytes, offset: 4 bytes
__bptr : typed pointer type, size: 4 bytes, offset: 8 bytes
structure has been padded, size: 4 bytes, offset: 36 bytes
overloaded name C
instance C::C(void)
instance C::C(const C &)
!!
!! Displaying information about base classes
!!
DBG> SHOW SYMBOL /FULL B1
type B1
struct (B1, 8 components), size: 24 bytes
inherits: virtual A
is inherited by: C
contains the following members:
i : longword integer, size: 4 bytes, offset: 0 bytes
overloaded name B1
void f(void)
B1 & =(const B1 &)
void h(void) [virtual]
__vptr : typed pointer type, size: 4 bytes, offset: 4 bytes
__bptr : typed pointer type, size: 4 bytes, offset: 8 bytes
structure has been padded, size: 12 bytes, offset: 12 bytes
overloaded name B1
instance B1::B1(void)
instance B1::B1(const B1 &)
!!
!! Displaying class member information
!!
DBG> SHOW SYMBOL /FULL j
record component C::j
address: offset 24 bytes from beginning of record
atomic type, longword integer, size: 4 bytes
record component A::j
address: offset 4 bytes from beginning of record
atomic type, longword integer, size: 4 bytes
!!
!! Simple object display
!!
DBG> EXAMINE a
CXXDOCEXAMPLE\main\a: struct A
i: 0
j: 1
__vptr: 131168
!!
!! Using *, -> and . to access objects and members
!!
DBG> EXAMINE ptr
CXXDOCEXAMPLE\main\ptr: 40
DBG> EXAMINE *ptr
*CXXDOCEXAMPLE\main\ptr: struct A
i: 0
j: 1
__vptr: 131168
DBG> EXAMINE a.i
CXXDOCEXAMPLE\main\a.i: 0
DBG> EXAMINE ptr->i
CXXDOCEXAMPLE\main\ptr->i: 0
!!
!! Complicated object example
!!
DBG> EXAMINE c
CXXDOCEXAMPLE\main\c: struct C
inherit B1
inherit virtual A
i: 8
j: 9
__vptr: 131200
i: 10
__vptr: 131232
__bptr: 131104
inherit B2
inherit virtual A (already printed, see above)
i: 11
__vptr: 131280
__bptr: 131152
j: 12
__vptr: 131232
__bptr: 131104
!!
!! The debugger using C++ symbol lookup rules (to match c.j)
!! and then the use of :: to specify a particular member named j.
!!
DBG> EXAMINE c.j
CXXDOCEXAMPLE\main\c.j: 12
DBG> EXAMINE c.A::j
CXXDOCEXAMPLE\main\c.A::j: 9
!!
!! Using the global scope resolution operator.
!!
DBG> EXAMINE x
CXXDOCEXAMPLE\main\x: 101
DBG> EXAMINE ::x
CXXDOCEXAMPLE\x: 13
!!
!! Handling ambiguous member references.
!!
DBG> EXAMINE c.i
%DEBUG-I-AMBIGUOUS, 'i' is ambiguous, matching the following
CXXDOCEXAMPLE\main\c.B1::i
CXXDOCEXAMPLE\main\c.B2::i
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> EXAMINE c.B1::i
CXXDOCEXAMPLE\main\c.B1::i: 10
!!
!! Refering to static data members: with . and with ::
!!
DBG> EXAMINE c.s
CXXDOCEXAMPLE\main\c.s: 42
DBG> EXAMINE C::s
C::s: 42
!!
!! Setting watchpoints on objects. All non-static data members
!! are watched (including those in base classes). Static data
!! members are not watched. Of course watchpoints on static data
!! members can be set explicitly.
!!
DBG> SET WATCH c
%DEBUG-I-WPTTRACE, non-static watchpoint, tracing every instruction
DBG> GO
watch of CXXDOCEXAMPLE\main\c.i at CXXDOCEXAMPLE\main\%LINE 50+8
50: c.B2::i++;
old value: 11
new value: 12
break at CXXDOCEXAMPLE\main\%LINE 51
51: c.s++;
DBG> SET WATCH c.s
DBG> GO
watch of CXXDOCEXAMPLE\main\c.s at CXXDOCEXAMPLE\main\%LINE 51+16
51: c.s++;
old value: 43
new value: 44
break at CXXDOCEXAMPLE\main\%LINE 53
53: b1.f();
!!
!! Basic member lookup applies to functions.
!!
DBG> EXAMINE /SOURCE b1.f
module CXXDOCEXAMPLE
14: void f() {}
DBG> SET BREAK B1::f
DBG> GO
break at routine B1::f
14: void f() {}
!!
!! Support for 'this'.
!!
DBG> EXAMINE this
B1::f::this: 16
DBG> EXAMINE *this
*B1::f::this: struct B1
inherit virtual A
i: 2
j: 3
__vptr: 131184
i: 4
__vptr: 131248
__bptr: 131120
DBG> EXAMINE this->i
B1::f::this->i: 4
DBG> EXAMINE this->j
B1::f::this->A::j: 3
DBG>EXAMINE i
B1::f::this->i: 4
DBG> EXAMINE j
B1::f::this->A::j: 3
!!
!! Support for virtual functions.
!!
!! We are at the call to B1::f made at 'b1.f()'.
!! Here this->h matches B1::h.
!!
DBG> EXAMINE /SOURCE %LINE 53
module CXXDOCEXAMPLE
53: b1.f();
DBG> SET BREAK this->h
DBG> SHOW BREAK
breakpoint at routine B1::f
breakpoint at routine B1::h
!!
!! We are at the call to B1::f made at 'c.B1::f()'.
!! Here this->h matches C::h.
!!
DBG> GO
break at routine B1::f
14: void f() {}
DBG> EXAMINE /SOURCE %LINE 54
module CXXDOCEXAMPLE
54: c.B1::f();
DBG> SET BREAK this->h
DBG> SHOW BREAK
breakpoint at routine B1::f
breakpoint at routine B1::h
breakpoint at routine C::h
!!
!! Handling overloaded functions
!!
DBG> SET BREAK g
%DEBUG-I-NOTUNQOVR, symbol 'g' is overloaded
overloaded name C::g
instance C::g(int)
instance C::g(long)
instance C::g(char)
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> SET BREAK g(int)
DBG> CANCEL BREAK/ALL
!!
!! Working with constructors, destructors, and operators.
!!
DBG> SET BREAK C
%DEBUG-I-NOTUNQOVR, symbol 'C' is overloaded
overloaded name C
instance C::C(void)
instance C::C(const C &)
%DEBUG-E-REENTER, reenter the command using a more precise pathname
DBG> SHOW SYMBOL /FULL ~C
routine C::~C
type signature: ~C(void)
code address: #, size: 152 bytes
procedure descriptor address: #
DBG> SET BREAK %NAME'~C'
DBG> SET BREAK %NAME'=='
%DEBUG-W-UNALLOCATED, '==' is not allocated in memory (optimized away)
%DEBUG-E-CMDFAILED, the SET BREAK command has failed
DBG> SHOW SYMBOL /FULL ==
routine C::==
type signature: int ==(C &)
address: unallocated
DBG> SHOW BREAK
breakpoint at routine C::~C
DBG> EXIT
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