From 8e97f45f88aeb2ac83cde4910a9216d970a4c0f7 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Thu, 14 Aug 2003 05:27:18 +0000
Subject: [PATCH] Document threading status.
Update to POSIX getpwuid_r() function.
---
src/port/thread.c | 51 +++++++++++++++++++++++++++++++++++++----------
1 file changed, 40 insertions(+), 11 deletions(-)
diff --git a/src/port/thread.c b/src/port/thread.c
index d4c3909e594..df06f118c6f 100644
--- a/src/port/thread.c
+++ b/src/port/thread.c
@@ -7,13 +7,41 @@
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
*
- * $Id: thread.c,v 1.2 2003/08/08 03:09:56 momjian Exp $
+ * $Id: thread.c,v 1.3 2003/08/14 05:27:18 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
+/*
+ * Threading sometimes requires specially-named versions of functions
+ * that return data in static buffers, like strerror_r() instead of
+ * strerror(). Other operating systems use pthread_setspecific()
+ * and pthread_getspecific() internally to allow standard library
+ * functions to return static data to threaded applications.
+ *
+ * Additional confusion exists because many operating systems that
+ * use pthread_setspecific/pthread_getspecific() also have *_r versions
+ * of standard library functions for compatibility with operating systems
+ * that require them. However, internally, these *_r functions merely
+ * call the thread-safe standard library functions.
+ *
+ * For example, BSD/OS 4.3 uses Bind 8.2.3 for getpwuid(). Internally,
+ * getpwuid() calls pthread_setspecific/pthread_getspecific() to return
+ * static data to the caller in a thread-safe manner. However, BSD/OS
+ * also has getpwuid_r(), which merely calls getpwuid() and shifts
+ * around the arguments to match the getpwuid_r() function declaration.
+ * Therefore, while BSD/OS has getpwuid_r(), it isn't required. It also
+ * doesn't have strerror_r(), so we can't fall back to only using *_r
+ * functions for threaded programs.
+ *
+ * The current setup is to assume either all standard functions are
+ * thread-safe (NEED_REENTRANT_FUNC_NAMES=no), or the operating system
+ * requires reentrant function names (NEED_REENTRANT_FUNC_NAMES=yes).
+ */
+
+
/*
* Wrapper around strerror and strerror_r to use the former if it is
* available and also return a more useful value (the error string).
@@ -34,19 +62,20 @@ pqStrerror(int errnum, char *strerrbuf, size_t buflen)
/*
* Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
- * behaviour, if it is not available.
+ * behaviour, if it is not available or required.
*/
int
-pqGetpwuid(uid_t uid, struct passwd * resultbuf, char *buffer,
- size_t buflen, struct passwd ** result)
+pqGetpwuid(uid_t uid, struct passwd *resultbuf, char *buffer,
+ size_t buflen, struct passwd **result)
{
#if defined(USE_THREADS) && defined(HAVE_GETPWUID_R)
-
/*
- * broken (well early POSIX draft) getpwuid_r() which returns 'struct
- * passwd *'
+ * Early POSIX draft of getpwuid_r() returns 'struct passwd *'.
+ * getpwuid_r(uid, resultbuf, buffer, buflen)
+ * Do we need to support it? bjm 2003-08-14
*/
- *result = getpwuid_r(uid, resultbuf, buffer, buflen);
+ /* POSIX version */
+ getpwuid_r(uid, resultbuf, buffer, buflen, result);
#else
/* no getpwuid_r() available, just use getpwuid() */
*result = getpwuid(uid);
@@ -56,13 +85,13 @@ pqGetpwuid(uid_t uid, struct passwd * resultbuf, char *buffer,
/*
* Wrapper around gethostbyname() or gethostbyname_r() to mimic
- * POSIX gethostbyname_r() behaviour, if it is not available.
+ * POSIX gethostbyname_r() behaviour, if it is not available or required.
*/
int
pqGethostbyname(const char *name,
- struct hostent * resbuf,
+ struct hostent *resbuf,
char *buf, size_t buflen,
- struct hostent ** result,
+ struct hostent **result,
int *herrno)
{
#if defined(USE_THREADS) && defined(HAVE_GETHOSTBYNAME_R)