C / C++ / MFC

Zdeslav Vojkovic wrote:

if an exception is allocated on the heap (using 'new' operator), it must be caught through a pointer.

Zdeslav Vojkovic wrote:

however, this is not a good practice because it is not obvious to the client code how to handle it, and it complicates the deleting of the allocated exception instance (who will call delete on it).

Zdeslav Vojkovic wrote:

exceptions shoud be stack allocated, thrown, and caught by reference.

Zdeslav Vojkovic wrote:

MFC implements somewhat specific idiom, where exceptions are allocated on the heap and you have to call Delete() method of the CException class to destroy the instance

Britley wrote:

Why must? Why cannot it be accessed through reference?

T x;<br />
T& ref = x; // valid<br />
T* ptr = x; // not valid

Britley wrote:

If the exception is stack allocated, should we make sure the catch statement is in the same scope(braces) as that of the exception variable

Britley wrote:

What is the equivalent for the C++ "exception" class to free the object?

Britley wrote:

Btw, this Delete method of CException might destroy the instance to free up resources, but is the object itself freed too (perhaps through 'delete this')?

Zdeslav Vojkovic wrote:

because T* can't be treated as T, while T& can (they are interchangeable).

<br />
try {<br />
  T *t = new T;<br />
  throw *t;<br />
}catch(T& te) {<br />
}<br />

Zdeslav Vojkovic wrote:

What is the equivalent for the C++ "exception" class to free the object

Zdeslav Vojkovic wrote:

delete operator.

Britley wrote:

Anything wrong, other than the memory leak, ofcourse?

Britley wrote:

Why do you need to call Delete on the MFC CException again

Britley wrote:

What is the equivalent for the C++ "exception" class to free the object?

Zdeslav Vojkovic wrote:

3. any class/type can be exception tpye, but maybe you would like to have look at the 'exception' class, which is a base class for all exeption classes in standard c++ library

Britley wrote:

I started using try/catch(...) in C++, but not sure what all can be done in the catch block.

Britley wrote:

1. What does the elipsis (...) mean?

Britley :->wrote:

What else can be put here?

Britley wrote:

If so, how do you define an exception class? Is there an interface that we should implement?

Britley wrote:

4. When we have the elipsis(...) how do you get the details of the exception?

Britley wrote:

5. Are there simple examples anywhere that demonstrate exceptions in C++ for Java programmers

<br />
TRY<br />
{<br />
CDatabase DB;<br />
CRecordset Rc;<br />
CString szSql = "SELECT * FROM MYTABLE WHERE AGE = 20"<br />
DB.ExecuteSql(szSql);<br />
}CATCH(CDatabaseException CDbe){ AfxMessageBox(CDBE->m_error));}<br />

Aljechin wrote:

Eg: catch(CFileException Cfe)

Aljechin wrote:

There is one API call known as GetLastError for this purpose

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

Yuwraj wrote:

I have to write a code which contain connect method and which connect's

to server.

"The words of God are not like the oak leaf which dies and falls to the earth, but like the pine tree which stays green forever." - Native American Proverb

#include <windows.h>
#include <stdio.h>
#include "psapi.h"

void PrintProcessNameAndID( DWORD processID )
{
    char szProcessName[MAX_PATH] = "unknown";

    // Get a handle to the process.

    HANDLE hProcess = OpenProcess( PROCESS_QUERY_INFORMATION |
                                   PROCESS_VM_READ,
                                   FALSE, processID );

    // Get the process name.

    if (NULL != hProcess )
    {
        HMODULE hMod;
        DWORD cbNeeded;

        if ( EnumProcessModules( hProcess, &hMod, sizeof(hMod), 
             &cbNeeded) )
        {
            GetModuleBaseName( hProcess, hMod, szProcessName, 
                               sizeof(szProcessName) );
        }
        else return;
    }
    else return;

    // Print the process name and identifier.

    printf( "%s (Process ID: %u)\n", szProcessName, processID );

    CloseHandle( hProcess );
}

void main( )
{
    // Get the list of process identifiers.

    DWORD aProcesses[1024], cbNeeded, cProcesses;
    unsigned int i;

    if ( !EnumProcesses( aProcesses, sizeof(aProcesses), &cbNeeded ) )
        return;

    // Calculate how many process identifiers were returned.

    cProcesses = cbNeeded / sizeof(DWORD);

    // Print the name and process identifier for each process.

    for ( i = 0; i < cProcesses; i++ )
        PrintProcessNameAndID( aProcesses[i] );
}

Love Forgives--Love Gives--Jesus is Love

"The words of God are not like the oak leaf which dies and falls to the earth, but like the pine tree which stays green forever." - Native American Proverb