Re: Memory allocation with malloc

From:
peter koch <peter.koch.larsen@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 15 Nov 2007 15:37:07 -0800 (PST)
Message-ID:
<614a0300-99c7-44e8-a8b4-7af7fc2b03b7@o6g2000hsd.googlegroups.com>
On 16 Nov., 00:27, PSN <prakash...@gmail.com> wrote:

Hello everyone,

int main()
{
        char *pChar;
        pChar = (char *)malloc(16);
        memcpy(pChar, "AAAAAAAAAAAAAAA", 16);
        printf ("***%s***\n", pChar);

        realloc(pChar, 28);
        memcpy(pChar, "BBBBBBBBBBBBBBBBBBBBBBBBBBB", 28);
        printf ("***%s***\n", pChar);

        free(pChar);
        return 0;

}

Can someone please explain me why does this crash. what am i doing
wrong ??

Can you explain why you use malloc when you have the opportunity to
use std::string or std::vector (assuming you program in C++ as you
would otherwise be off-topic)?

realloc often allocates a new buffer, copies the content and frees the
old buffer - e.g.

void* realloc(void* ptr,size_t new_size)
{
    void* new_area = malloc(new_size);
    memcpy(new_area,ptr,size_allocated(ptr)); // size_allocated is not
an official function
    free(ptr);
    return new_area;
}

And you forget to update pChar with the result of the realloc call.

/Peter

Thank you for youri time

Prakash

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