C++ Help about ZeroMemory - c++

Question

I defined my char as usual, although I named it buf. I keep getting an error:
argument of type 'char' is incompatible with parameter of type 'void*'
If I set buf to void*, it won't be able to pass in 4096 as a parameter.
So, how do I get around this? Has anyone run into a problem like this before?
char buf{4096};
string userinput;
do
{
cout << "> " << endl;
getline(cin, userinput);
if (userinput.size() > 0) // make sure the user typed something in
{
int SendResult = send(sock, userinput.c_str, userinput.size() + 1, 0);
if (SendResult != SOCKET_ERROR)
{
ZeroMemory(buf, 4096);
int bytesReceived = recv(sock, buf, 4096, 0);
if (bytesReceived > 0)
{
cout << "SERVER" << string(buf, 0, bytesReceived) <<
endl;
}
}
}

Answer 1

The problem is likely this definition:
char buf{4096};
Which is roughly equivalent to:
char buf = 4096;
Which is a single character, not a character array buffer. To fix this:
char buf[4096];
When passing that in you may need to do:
ZeroMemory(&buf, 4096);
I'd strongly encourage you to avoid hammering out 4096 everywhere, so define a constant:
const SIZE_T buf_size = 4096;
char buf[buf_size];
// ...
ZeroMemory(&buf, buf_size);

Answer 2

How about:
#include <array>
std::array<char, 4096> buf;
...
std::fill(buf.begin(), buf.end(), 0);
int bytesReceived = recv(sock, buf.data(), buff.size(), 0);
...

Answer 3

Another question is why do you need ZeroMemory at all. And I think what happened here is that you picked up wrong string constructor overload. Let me explain:
You have your buf buffer and you have your bytesReceived length of data, so really all you need is
std::string(buf, bytesReceived)
to construct valid string. But you have chosen
std::string(buf, 0, bytesReceived)
This overload looks like this:
basic_string( const basic_string& other,
size_type pos,
size_type count,
..
The buf is implicitly converted into std::string at the 1st argument, but for this to work correctly your buffer needs to be null terminated, which it might or might not be. So you worked around this problem by zeroing the rest of the buffer. What do you think will happen if you get 4096 bytes of data that is not null terminated? Your workaround will not work in this case. So just use the appropriate string constructor mentioned above and you won't need to use ZeroMemory.

Answer 4

Use char buf[4096]; instead of buf{4096}
use buf as an array then Fill the block of memory with zeros
by the way, do you really know what does buf{4096} do??
if you do that it means that you want to put this number 4096
which will be converted to "(`" because the buf data type is char so you have used wrong way.
ZeroMemory(buf, 4096);
// Wait for client to send data
int bytesReceived = recv(clientSocket, buf, 4096, 0);
if (bytesReceived == SOCKET_ERROR)
{
cerr << "Error in recv(). Quitting" << endl;
break;
}