C / C++ / MFC

Sarath. wrote:

B will be partially constructed without knowing that, C completed it's initialization.

Sarath. wrote:

misunderstand that the whole construction was successful and will start using partially constructed objects.

George_George wrote:

I think when there is exception in B's constructor, the exception will also be thrown to C's constructor.

George_George wrote:

(So, C will always be aware of that whether or not B's constructor fails with exceptions)

George_George wrote:

So, C will know its sub-components failed to be initialized in C's catch handler block

class B
{
private:

int* p;

public:

    A (int* input) : p(input)
    try
    {

        // there are some other exceptions here

    }
    catch (bad_alloc)
    {
        // do not delete since bad_alloc means memory pointed by p is not allocated
        // re-throw exception to C to indicate the fail of creation of B
    }
    catch (...)
    {
        // if we do not delete p, there will be memory leak
        if (p) delete[] p;
        // re-throw exception to C to indicate the fail of creation of B
    }
}

George_George wrote:

Maybe I have not made my ideas clear enough.

int foo[100];
B(foo);

George_George wrote:

A (int* input) : p(input)

B (int* input) : p(input)

int *p;
p = new int[25];
assert(p); // here George knows p is valid.
B b(p);
// here George doesn't know if p is still valid
// because B may have deleted (or not) it under the hood.

George_George wrote:

I assume that you mean if p always pointed to some object on heap, my code is bug free.

int * p;
p = new int[10];
assert(p);
// fill p with some important data
...
...
B b(p);
// BUG: if B throws, here p is invalid and the important data is lost

George_George wrote:

I extract my issue in a simple way, and we should discuss under in this simple and special condition.

<br />
Byte-order mark Description <br />
----------------------------<br />
EF BB BF        : UTF-8<br />
FF FE           : UTF-16, little endian<br />
FE FF           : UTF-16, big endian<br />
FF FE 00 00     : UTF-32, little endian<br />
00 00 FE FF     : UTF-32, big-endian

Ajay L D wrote:

WriteFile(fpNew, str, sizeof(str), &dwNumBytesWritten, NULL);

WriteFile(fpNew, str, dwNumBytesRead, &dwNumBytesWritten, NULL);

George_George wrote:

1. whether or not we are using auto_ptr to allocate new object on heap (using new), there may be bad_alloc exceptions;

George_George wrote:

when we met with such exceptions, we catch it (bad_alloc)

George_George wrote:

and try to mininize the operation in catch handler block (since when bad_alloc occurs, it means memory is running out, we can not do anything complex in handler).

George_George wrote:

If we met with bad_alloc, do we need to use delete or delete[] to free the memory in exception handler block?