Re: [PATCH v2 06/14] mingw: use real pid

From

Erik Faye-Lund <kusmabite@googlemail.com>

Date

Jan 18, 2010, 22:33 UTC

Message-ID

<40aa078e1001181433v3c86f147wf3e6aace4501c1a8@mail.gmail.com>

In-Reply-To

<40aa078e1001160112k68c0daafnd6abcb715e1176fe@mail.gmail.com>

> On Sat, Jan 16, 2010 at 9:03 AM, Johannes Sixt <j6t@kdbg.org> wrote:
>> On Freitag, 15. Januar 2010, Erik Faye-Lund wrote:
>>> On Fri, Jan 15, 2010 at 11:30 PM, Johannes Sixt <j6t@kdbg.org> wrote:
>>> > On Freitag, 15. Januar 2010, Erik Faye-Lund wrote:
>>> >> @@ -729,7 +729,7 @@ static pid_t mingw_spawnve(const char *cmd, const
>>> >> char **argv, char **env, return -1;
>>> >>       }
>>> >>       CloseHandle(pi.hThread);
>>> >> -     return (pid_t)pi.hProcess;
>>> >> +     return (pid_t)pi.dwProcessId;
>>> >>  }
>>> >
>>> > You are not using the pi.hProcess anymore, so you must close it.
>>>
>>> No. If I do, the pid becomes invalid after the process is finished,
>>> and waitpid won't work. I couldn't find anywhere were we actually were
>>> closing the handle, even after it was finished. So I don't think we
>>> leak any more than we already did (for non-daemon purposes).
>>
>> Previously, this handle was closed by _cwait() (it was the "pid"), so we
>> didn't leak it.
>
> Oh, I see. My planned route with this (before I looked for where the
> handle was closed), was to maintain some sort of list of each started
> PID and their handle, and lookup in that list instead of using
> OpenProcess. I guess that would solve the problem here, but it feels a
> bit nasty. Not as nasty as introducing a leak, though.
>

What I had in mind was something along these lines:

diff --git a/compat/mingw.c b/compat/mingw.c
index e2821b3..71201d0 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -638,6 +638,13 @@ static int env_compare(const void *a, const void *b)
 	return strcasecmp(*ea, *eb);
 }

+struct pid_info {
+	pid_t pid;
+	HANDLE proc;
+};
+static struct pid_info *pinfo;
+static int num_pinfo;
+
 static pid_t mingw_spawnve(const char *cmd, const char **argv, char **env,
 			   int prepend_cmd)
 {
@@ -729,6 +736,13 @@ static pid_t mingw_spawnve(const char *cmd, const
char **argv, char **env,
 		return -1;
 	}
 	CloseHandle(pi.hThread);
+
+	/* store process handle */
+	num_pinfo++;
+	pinfo = xrealloc(pinfo, sizeof(struct pid_info) * num_pinfo);
+	pinfo[num_pinfo - 1].pid = pi.dwProcessId;
+	pinfo[num_pinfo - 1].proc = pi.hProcess;
+
 	return (pid_t)pi.dwProcessId;
 }

@@ -1536,6 +1550,7 @@ int waitpid(pid_t pid, int *status, unsigned options)
 	}

 	if (options == 0) {
+		int i;
 		if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0) {
 			CloseHandle(h);
 			return 0;
@@ -1544,6 +1559,19 @@ int waitpid(pid_t pid, int *status, unsigned options)
 		if (status)
 			GetExitCodeProcess(h, (LPDWORD)status);

+		for (i = 0; i < num_pinfo; ++i)
+			if (pinfo[i].pid == pid)
+				break;
+
+		if (i < num_pinfo) {
+			CloseHandle(pinfo[i].proc);
+			memmove(pinfo + i, pinfo + i + 1,
+			    sizeof(struct pid_info) * (num_pinfo - i - 1));
+			num_pinfo--;
+			pinfo = xrealloc(pinfo,
+			    sizeof(struct pid_info) * num_pinfo);
+		}
+
 		CloseHandle(h);
 		return pid;
 	}

-- 
Erik "kusma" Faye-Lund