win32

只需要记住使用OpenEvent来同步Event对象。

Project A:

#define _CRT_SECURE_NO_WARNINGS
#include <Windows.h>
#include <stdio.h>
#include <time.h>

HANDLE hEvent;

int main()
{
    hEvent = CreateEvent(NULL, TRUE, FALSE, L"Ev");
    if (hEvent == NULL) {
        printf("Error event");
        return -1;
    }

    PROCESS_INFORMATION pi;
    STARTUPINFO si;
    memset(&si, 0, sizeof(si));
    si.cb = sizeof(si);

    if (!SetEvent(hEvent)) {
        printf("Setevent error
");
        return -1;
    }

    if (!CreateProcess(L"Project B.exe", NULL, NULL, NULL, FALSE, 0, NULL, NULL, &si, &pi)) {
        printf("Cannot create process.
");
        return -1;
    }
    Sleep(3000); //这边需要延时关闭该进程，以便Project B有足够的时间获取hEvent对象

    CloseHandle(hEvent);
}

Project B:

#define _CRT_SECURE_NO_WARNINGS
#include <Windows.h>
#include <stdio.h>
#include <time.h>

HANDLE hEvent;

int main()
{
    hEvent = OpenEvent(EVENT_MODIFY_STATE | SYNCHRONIZE, FALSE, L"Ev"); //要有SYNCHRONIZE标志，这是同步所必须的
    
    DWORD res;
    while (true)
    {

        res = WaitForSingleObject(hEvent, INFINITE);
        if (res == WAIT_OBJECT_0) {
            printf("Hello world!
");
            break;
        }
    }
    CloseHandle(hEvent);
    return 0;
}