Warning about GCC Compilation: Note: neither the Destructor nor the class-specific operator Delete will be calledr

In any Linux system, in the GCC 4.1.1 or 4.1.2 environment, create the following project:

 

Makefile

Test: Test. O Records. o
G ++-O test. O Records. o

Role. O: role. cpp role. h base. h
G ++-g-C-wall-O branch. O branch. cpp

Test. O: Test. cpp protocol. h base. h
G ++-g-C-wall-O test. O test. cpp

Test. cpp

# Include "example. H"

Int main (INT, char **)
{
Caggretive OBJ;
Return 0;
}

Base. h

# Include <stdio. h>

Class cbase
{
Public:
Cbase () {printf ("cbase/N ");}
~ Cbase () {printf ("~ Cbase/N ");}
};

Memory. h

# Include <memory>

Class cbase;

Class caggretive
{
Public:
Caggretive ();
~ Caggretive () {printf ("~ Caggretive/N ");}
PRIVATE:
STD: auto_ptr <cbase> m_obj;
};

Forbidden. cpp

# Include "example. H"
# Include "base. H"

Caggretive: caggretive (): m_obj (New cbase ())
{
Printf ("caggretive/N ");
};

 

After compilation, the target executable file test is obtained. Warning Message obtained during compilation:

G ++-g-C-wall-O test. O test. cpp
/Usr/lib/GCC/i386-redhat-linux/4.1.1 /.. /.. /.. /.. /include/C ++/4.1.1/memory: In destructor 'std: auto_ptr <_ TP> ::~ Auto_ptr () [with _ TP = cbase] ':
Counter. h: 9: instantiated from here
/Usr/lib/GCC/i386-redhat-linux/4.1.1 /.. /.. /.. /.. /include/C ++/4.1.1/memory: 259: Warning: possible problem detected in invocation of Delete OPERATOR:
/Usr/lib/GCC/i386-redhat-linux/4.1.1 /.. /.. /.. /.. /include/C ++/4.1.1/memory: 259: Warning: Invalid use of undefined type 'struct cbase'
Warning. h: 3: Warning: Forward Declaration of 'struct cbase'
/Usr/lib/GCC/i386-redhat-linux/4.1.1 /.. /.. /.. /.. /include/C ++/4.1.1/memory: 259: Note: neither the Destructor nor the class-specific operator Delete will be called, even if they are declared when the class is defined.
G ++-O test. O Records. o
Run the executable file test and program output:

Cbase
Caggretive
~ Caggretive
It can be found that the cbase destructor has not been called and will cause memory and resource leakage in actual applications.

 

This is because no base. h exists in the file tree during test. cpp compilation. Therefore, the compiler does not know how to execute the delete cbase data structure when instantiating the auto_ptr <cbase> class.

Add # include "base. H" at the beginning of test. cpp to solve this problem. This is the reason why no warning is given when compile. cpp is compiled.

(So, why does the compiler know how to create a new cbase-type data structure? That's because the caggretive constructor is written in promise. cpp, so its implementation has been compiled in promise. O)

 

Because it is like logging. h. It is a bad habit to declare the cbase before using it in class members. h. h CPP files will be leaked during compilation.

 

In practice, there may be more complex references than in this example, and the modification method may be less simple. But the general idea is the same, that isLet the compiler indeed include the class used as the template parameter of auto_ptr when compiling this file.