C++ getting error C2440 - c++

Question

Hello I'm using Visual Studio c++ 2010
I'm having a problem with this code ( it's taken from C language code ) :
MEMBLOCK* create_memblock (HANDLE hProc, MEMORY_BASIC_INFORMATION *meminfo)
{
MEMBLOCK *mb = malloc(sizeof(MEMBLOCK));
if (mb)
{
mb->hProc = hProc;
mb->addr = meminfo->BaseAddress;
mb->size = meminfo->RegionSize;
mb->buffer = malloc(meminfo->RegionSize);
mb->next = NULL;
}
return mb;
}
I'm having these errors :
error C2440: 'initializing' : cannot convert from 'void *' to 'MEMBLOCK *'
error C2440: '=' : cannot convert from 'PVOID' to 'unsigned char *'
error C2440: '=' : cannot convert from 'void *' to 'unsigned char *'
I'm kinda newbie. Can you please provide a converted code for this that actually works with c++.
Thank you

Answer 1

Since you're programming in C++, you should not use the old C function malloc. Instead I would recommend that you use the C++ new construct:
MEMBLOCK *mb = new MEMBLOCK;

Answer 2

In C++ You may not assign a pointer of type void * to a pointer of some other type. So for example instead of writing
MEMBLOCK *mb = malloc(sizeof(MEMBLOCK));
You have to write
MEMBLOCK *mb = ( MEMBLOCK * )malloc(sizeof(MEMBLOCK));
Also you have to change other statements where there is the same problem. It seems these statements are
mb->addr = ( unsigned char * )meminfo->BaseAddress;
mb->buffer = ( unsigned char * )malloc(meminfo->RegionSize);
It is a good example of that you always should use an explicit casting even in C. That makes the code more safe and clear.

Answer 3

malloc() returns void*, and C++ does not automatically cast void* to a different pointer type. So you have to cast the return value:
MEMBLOCK *mb = (MEMBLOCK*) malloc(sizeof(MEMBLOCK));
Try:
MEMBLOCK* create_memblock (HANDLE hProc, MEMORY_BASIC_INFORMATION *meminfo)
{
MEMBLOCK *mb = (MEMBLOCK*)malloc(sizeof(MEMBLOCK));
if (mb)
{
mb->hProc = hProc;
mb->addr = meminfo->BaseAddress;
mb->size = meminfo->RegionSize;
mb->buffer = malloc(meminfo->RegionSize);
mb->next = NULL;
}
return mb;
}