Document threading status.

Update to POSIX getpwuid_r() function.

diff --git a/src/port/thread.c b/src/port/thread.c
index d4c3909e59447d89ca4351ea11f5138689e48697..df06f118c6f71960ecd9bac943fddcae5a93b354 100644 (file)
--- 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)