I tried creating two different visual c++ console applications for Inter Process Communication(IPC). The Build for both codes is successful.But,when I try to debug it, I get exception like this "Exception thrown at 0x00007FFF168E1657 (vcruntime140d.dll) in FileMapServer_Parent.exe: 0xC0000005: Access violation writing location 0x0000000000000000"
//PARENT PROCESS:
#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <Tlhelp32.h>
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <cstring>
#include <cctype>
#include <fstream>
using namespace std
int main()
{
cout << "\t\t.....FILEMAPPING SERVER or PARENT....." << endl;
cout << endl;
//Local Variable Definitions
HANDLE hFileMap;
BOOL bResult;
PCHAR lpBuffer = NULL;
char Buffer[256] = "Hello From File Map Server";
size_t szBuffer = size(Buffer);
// STEP 1 : Create File Map
hFileMap = CreateFileMapping(
INVALID_HANDLE_VALUE,
NULL,
PAGE_READWRITE,
0,
256,
L"LOCAL\\MyFileMap);
if (hFileMap == FALSE)
{
cout << "CreateFileMapping Failed & Error Number - " << GetLastError() << endl;
}
else
cout << "CreateFileMapping Success - " << endl;
// STEP 2 : Map View of File
lpBuffer = (PCHAR)MapViewOfFile(
hFileMap,
FILE_MAP_ALL_ACCESS,
0,
0,
256);
if (lpBuffer == NULL)
{
cout << "MapViewOf File Failes & Error No - " << GetLastError() << endl;
}
else
cout << "MapViewOf File Success " << endl;
//STEP 3 : Copy Memory Function
CopyMemory(lpBuffer,Buffer,szBuffer);
//STEP 4 : Unmap View Of File
bResult = UnmapViewOfFile(lpBuffer);
if (bResult == FALSE)
{
cout << "UnMapViewOfFile Failed & Error No - " << GetLastError() << endl;
}
else
cout << "UnMapViewOfFile FSuccess - " << endl;
system("PAUSE");
return 0;
}
Exception while running parent process: [1]: https://i.sstatic.net/bomQB.png
//CHILD PREOCESS:
#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <Tlhelp32.h>
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <cstring>
#include <cctype>
#include <fstream>
using namespace std;
int main()
{
cout << "\t\t.....FILEMAPPING CLIENT or CHILD....." << endl;
cout << endl;
// Local Variable Definitions
HANDLE hFileMap;
BOOL bResult;
PCHAR lpBuffer = NULL;
// STEP 1 : OpenFileMapping
hFileMap = OpenFileMapping(
FILE_MAP_ALL_ACCESS,
FALSE,
L"LOCAL\\MyFileMap");
if(hFileMap == NULL)
{
cout << "OpenFileMap Failed & error - " << GetLastError() << endl;
}
else
cout << "OpenFileMap success " << endl;
//STEP 2 : MapViewOfFile
lpBuffer = (PCHAR)MapViewOfFile(
hFileMap,
FILE_MAP_ALL_ACCESS,
0,
0,
256);
if (lpBuffer == NULL)
{
cout << "MapViewOf File Failes & Error No - " << GetLastError() << endl;
}
else
cout << "MapViewOf File Success " << endl;
//STEP 3 : Reading the data from File Map Object
cout << "DATA READING FROM PARENT PROCESS--->" <<lpBuffer<< endl;
//STEP 4 : UnMapViewOfFile
bResult = UnmapViewOfFile(lpBuffer);
if (bResult == FALSE)
{
cout << "UnMapViewOfFile Failed & Error No - " << GetLastError() << endl;
}
else
cout << "UnMapViewOfFile FSuccess - " << endl;
//STEP 5 : Close Handle
CloseHandle(hFileMap);
system("PAUSE");
return 0;
}
The problem is here:
hFileMap = CreateFileMapping(
INVALID_HANDLE_VALUE,
NULL,
PAGE_READWRITE,
0,
256,
L"LOCAL\\MyFileMap");
From the documentation of Kernel object namespaces they are case sensitive so you must change LOCAL
to Local
for this to work.
In addition to the "Global\" prefix, client processes can use the "Local\" prefix to explicitly create an object in their session namespace. These keywords are case sensitive.
https://msdn.microsoft.com/en-us/library/aa382954(v=vs.85).aspx
While debugging this issue I also changed the code to exit if the mapping fails:
if (hFileMap == NULL)
{
cout << "CreateFileMapping Failed & Error Number - " << GetLastError() << endl;
return -1;
}
else
cout << "CreateFileMapping Success - " << endl;
This avoided the crash with the original "LOCAL" (mapping failed).