Re: invalid conversion from void* to int**

From:
Rolf Magnus <ramagnus@t-online.de>
Newsgroups:
comp.lang.c++
Date:
Sun, 14 May 2006 13:27:25 +0200
Message-ID:
<e4746t$5dv$01$1@news.t-online.com>
Martin JQrgensen wrote:

Hi,

I'm using this alloc_mem-function:

- - - - - - - - - - - - - - - - - - - - - - - -

void *alloc_mem (size_t num_elems, size_t elem_size,
                   char *filename, int line,
                   size_t *total_mem)
{
    void *mem;
    size_t size = num_elems*elem_size;
    size += (sizeof (size_t) <= elem_size) ? elem_size
             : sizeof (size_t);
    mem = malloc(size);

    if (!mem)
    {
      fprintf(stderr, "%s: line %d, malloc(%lu) failed.\n",
              filename, line, (unsigned long) size);
      exit(EXIT_FAILURE);
    }

    /* save memory allocated for this pointer */
    memcpy(((char *)mem)+num_elems*elem_size,
           &size, sizeof size);
    *total_mem += size; /* update total memory allocated untill now */

    return mem;

}
- - - - - - - - - - - - - - - - - - - - - - - -

But I then declared some arrays like:

double **two_D_double;
int **two_D_int;
double *one_D_double;
int *one_D_int;
etc. etc...

MS visual studio 2005 + gcc doesn't complain. But with g++ I get such an
error as:

"invalid conversion from void* to int**" (the same for double **)

I was told I should ask about the g++ compiler here, although the code
is actually implemented in a C-program.


Don't use g++ for C programs. g++ is the C++ compiler.

So what's the language difference -


You didn't really think C and C++ were exactly the same, did you?

why can't I do an "implicit conversion
from void* to int**" in C++ ?


Because that's how the language is defined. Conversions from void* to any
other object pointer always need a cast.

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