Imposible declaration INT variable in my program - c++

Question

I tried to create a little project in C++ . My program should be able to read the currently running processes in Windows and send information about the processes to my private MySQL database every 5 minutes. In this amount of time I can read the processes.
See code below:
#include <stdio.h>
#include <iostream>
#include <windows.h>
#include <tlhelp32.h>
bool getAllProcesses(void);
int main(void){
getAllProcesses();
}
bool getAllProcesses(){
HANDLE WINAPI snapshot = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
LPPROCESSENTRY32 pe32;
Process32First(snapshot, pe32);
while(Process32Next(snapshot, pe32)){
std::cout << pe32->szExeFile << "\n";
}
std::cout << "End of list";
CloseHandle( snapshot );
return true;
}
The code above is working fine.
But if I add the code "int i;i=1;" like this:
#include <stdio.h>
#include <iostream>
#include <windows.h>
#include <tlhelp32.h>
bool getAllProcesses(void);
int main(void){
getAllProcesses();
}
bool getAllProcesses(){
int i;
i=0;
HANDLE WINAPI snapshot = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
LPPROCESSENTRY32 pe32;
Process32First(snapshot, pe32);
while(Process32Next(snapshot, pe32)){
std::cout << pe32->szExeFile << "\n";
}
std::cout << "End of list";
CloseHandle( snapshot );
return true;
}
With this change the program will crash, showing the alert "Program stop the work".
I tried to find the problem and I've determined the following :
If I use the function Process32First() OR Process32Next() I can't declare the same int in all of the program.
What is the problem?

Answer 1

You have a lot of issues going on here. I tried this on VS 2008 Win7.
The "i" declaration has nothing to do with the problem, but may just be moving the stack a bit to hide the real problems. See my comments in the corrected code below.
bool getAllProcesses(){
int i;
i=0;
HANDLE WINAPI snapshot = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
/* replace LPPROCESSENTRY32 with PROCESSENTRY32. LP is just a define as
a pointer to a structure, so you did not actually allocate any memory for the
return of Process32First() to return the result into.
So you were probably overwriting stuff in the stack. */
PROCESSENTRY32 pe32;
/* need to initialize the structure properly. Memset may be overkill,
but better to see all zeros than garbage. dwSize must be
initialized as per the SDK documentation. */
memset(&pe32,0,sizeof(pe32) );
pe32.dwSize = sizeof(pe32);
BOOL result;
/* did not check the result from the call if TRUE/FALSE */
result = Process32First(snapshot, &pe32);
std::cout << "result =" << result << "\n";
while(Process32Next(snapshot, &pe32)){
std::cout << pe32.szExeFile << "\n";
}
std::cout << "End of list";
CloseHandle( snapshot );
return true;
}

Answer 2

The addition of those 2 lines making the program not able to run is just a coincidence. The program should not be running at all, since there are 2 major mistakes:
pe32 is an uninitialized pointer
dwSize member of PROCESSENTRY32 structure is not initialized as described in the [MS.Docs]: Process32First function:
The calling application must set the dwSize member of PROCESSENTRY32 to the size, in bytes, of the structure.
And a third, smaller mistake is that you are ignoring the process data returned by Process32First.
In order to make things work correctly, replace the following lines of your code:
LPPROCESSENTRY32 pe32;
Process32First(snapshot, pe32);
while(Process32Next(snapshot, pe32)){
std::cout << pe32->szExeFile << "\n";
, with:
PROCESSENTRY32 pe32;
pe32.dwSize = sizeof(PROCESSENTRY32);
if (Process32First(snapshot, &pe32))
{
do {
std::cout << pe32.szExeFile << "\n";
}
while (Process32Next(snapshot, &pe32));
}