I have a Windows command line application child.exe for which I wish to create a wrapper, parent.exe. I do this by spawning the child from the parent using CreateProcess:
int wmain(int argc, WCHAR *argv[]) {
STARTUPINFO startupInfo = createStartupInfo();
PROCESS_INFORMATION processInfo = {0};
if(CreateProcessW(
L"C:\\child.exe", NULL, NULL, NULL, FALSE,
CREATE_NEW_CONSOLE, NULL, NULL, &startupInfo, &processInfo
)) {
WaitForSingleObject(processInfo.hProcess, INFINITE);
CloseHandle(processInfo.hThread);
CloseHandle(processInfo.hProcess);
return 0;
} else {
return -1;
}
}
STARTUPINFO createStartupInfo() {
// Create and return a STARTUPINFO structure...
}
I now want the child process to be terminated when the parent process closes. Following another question, I am using Job Objects to do so:
// Create and initialise the job object:
HANDLE ghJob = CreateJobObject(NULL, NULL);
if (ghJob == NULL) { /* Error handling... */ }
else {
JOBOBJECT_EXTENDED_LIMIT_INFORMATION jeli = { 0 };
// Configure all child processes associated with the
// job to terminate when the parent closes:
jeli.BasicLimitInformation.LimitFlags =
JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
if (! SetInformationJobObject(
ghJob, JobObjectExtendedLimitInformation, &jeli, sizeof(jeli)
)) { /* Error handling... */ }
}
I then assign the created child process to this job via AssignProcessToJobObject:
if(CreateProcessW(...)) {
AssignProcessToJobObject(ghJob, processInfo.hProcess));
WaitForSingleObject(processInfo.hProcess, INFINITE);
...
} ...
This works: Because the newly created process is assigned to a job with JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE, the child process is automatically terminated when the parent process closes for whatever reason.
But here is my problem: I don't have control over child.exe. It spawns its own sub-processes (say grandchild.exe), so we have:
parent.exe -> child.exe -> grandchild.exe
Unfortunately, this "spawning of grandchild.exe" fails when I assign the job object to child.exe as above. I believe this is because grandchild.exe inherits my job definition but child.exe tries to apply its own job definition to grandchild.exe and fails because on Windows 7 a job may only be associated with a single job. The docs for AssignProcessToJobObject say that if one wishes to create processes that do not inherit the job from their parent, one has to use the CREATE_BREAKAWAY_FROM_JOB flag when calling CreateProcess. But the problem is that this call to CreateProcess happens inside child.exe, to which I have no access.
Can anybody think of a solution that allows child.exe to freely spawn its own (grand)child processes, while at the same time making it possible for me to terminate child.exe when parent.exe is closed?
