[PATCH v3 05/14] mingw: use real pid

[Erik Faye-Lund <kusmabite@gmail.com>]

The Windows port so far used process handles as PID. However,
this does not work consistently with getpid.

Change the code to use the real PID, and use OpenProcess to
get a process-handle. Store the PID and the process handle
in a table protected by a critical section, so we can safely
close the process handle later.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
---
 compat/mingw.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 compat/mingw.h |   10 ++-----
 2 files changed, 72 insertions(+), 8 deletions(-)

diff --git a/compat/mingw.c b/compat/mingw.c
index cc5eb2c..4582345 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -702,6 +702,13 @@ static int env_compare(const void *a, const void *b)
 	return strcasecmp(*ea, *eb);
 }
 
+struct {
+	pid_t pid;
+	HANDLE proc;
+} *pinfo;
+static int num_pinfo;
+CRITICAL_SECTION pinfo_cs;
+
 static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
 			      const char *dir,
 			      int prepend_cmd, int fhin, int fhout, int fherr)
@@ -794,7 +801,23 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
 		return -1;
 	}
 	CloseHandle(pi.hThread);
-	return (pid_t)pi.hProcess;
+
+	/*
+	 * The process ID is the human-readable identifier of the process
+	 * that we want to present in log and error messages. The handle
+	 * is not useful for this purpose. But we cannot close it, either,
+	 * because it is not possible to turn a process ID into a process
+	 * handle after the process terminated.
+	 * Keep the handle in a list for waitpid.
+	 */
+	EnterCriticalSection(&pinfo_cs);
+	num_pinfo++;
+	pinfo = xrealloc(pinfo, sizeof(*pinfo) * num_pinfo);
+	pinfo[num_pinfo - 1].pid = pi.dwProcessId;
+	pinfo[num_pinfo - 1].proc = pi.hProcess;
+	LeaveCriticalSection(&pinfo_cs);
+
+	return (pid_t)pi.dwProcessId;
 }
 
 static pid_t mingw_spawnve(const char *cmd, const char **argv, char **env,
@@ -1577,6 +1600,51 @@ char *getpass(const char *prompt)
 	return strbuf_detach(&buf, NULL);
 }
 
+pid_t waitpid(pid_t pid, int *status, unsigned options)
+{
+	HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
+	    FALSE, pid);
+	if (!h) {
+		errno = ECHILD;
+		return -1;
+	}
+
+	if (options == 0) {
+		int i;
+		if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0) {
+			CloseHandle(h);
+			return 0;
+		}
+
+		if (status)
+			GetExitCodeProcess(h, (LPDWORD)status);
+
+		EnterCriticalSection(&pinfo_cs);
+
+		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(*pinfo) * (num_pinfo - i - 1));
+			num_pinfo--;
+			pinfo = xrealloc(pinfo,
+			    sizeof(*pinfo) * num_pinfo);
+		}
+
+		LeaveCriticalSection(&pinfo_cs);
+
+		CloseHandle(h);
+		return pid;
+	}
+	CloseHandle(h);
+
+	errno = EINVAL;
+	return -1;
+}
+
 #ifndef NO_MINGW_REPLACE_READDIR
 /* MinGW readdir implementation to avoid extra lstats for Git */
 struct mingw_DIR
diff --git a/compat/mingw.h b/compat/mingw.h
index bbfcc0c..96ed931 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -153,13 +153,7 @@ static inline int mingw_unlink(const char *pathname)
 }
 #define unlink mingw_unlink
 
-static inline pid_t waitpid(pid_t pid, int *status, unsigned options)
-{
-	if (options == 0)
-		return _cwait(status, pid, 0);
-	errno = EINVAL;
-	return -1;
-}
+pid_t waitpid(pid_t pid, int *status, unsigned options);
 
 #ifndef NO_OPENSSL
 #include <openssl/ssl.h>
@@ -336,11 +330,13 @@ void free_environ(char **env);
 static int mingw_main(); \
 int main(int argc, const char **argv) \
 { \
+	extern CRITICAL_SECTION pinfo_cs; \
 	_fmode = _O_BINARY; \
 	_setmode(_fileno(stdin), _O_BINARY); \
 	_setmode(_fileno(stdout), _O_BINARY); \
 	_setmode(_fileno(stderr), _O_BINARY); \
 	argv[0] = xstrdup(_pgmptr); \
+	InitializeCriticalSection(&pinfo_cs); \
 	return mingw_main(argc, argv); \
 } \
 static int mingw_main(c,v)
-- 
1.7.3.1.51.ge462f.dirty