From eb2d0288ece14df1e00709496bcc6e44c9983faf Mon Sep 17 00:00:00 2001
From: neil <neil@fb15a70f-31f2-0310-bbcc-cdcc74a49acc>
Date: Thu, 9 Oct 2014 19:46:27 +0000
Subject: [PATCH]  - Do nothing if FDs are identical (as per POSIX).  -
 Deallocate new FD if it's already valid (as per POSIX).  - Improved AutoDoc
 and added comments.

git-svn-id: https://svn.aros.org/svn/aros/trunk/AROS@49699 fb15a70f-31f2-0310-bbcc-cdcc74a49acc
---
 compiler/posixc/dup2.c | 57 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 16 deletions(-)

diff --git a/compiler/posixc/dup2.c b/compiler/posixc/dup2.c
index e8c17f5db7..53940e36a5 100644
--- a/compiler/posixc/dup2.c
+++ b/compiler/posixc/dup2.c
@@ -1,5 +1,5 @@
 /*
-    Copyright © 1995-2012, The AROS Development Team. All rights reserved.
+    Copyright © 1995-2014, The AROS Development Team. All rights reserved.
     $Id$
 
     POSIX.1-2008 function dup2().
@@ -14,7 +14,7 @@
     NAME */
 #include <unistd.h>
 
-	int dup2 (
+	int dup2(
 
 /*  SYNOPSIS */
 	int oldfd,
@@ -24,18 +24,29 @@
 /*  FUNCTION
 	Duplicates a file descriptor.
 
-	The object referenced by the descriptor does not distinguish between oldd
-        and newd in any way.  Thus if newd and oldd are duplicate references to
-        an open file, read(),  write() and lseek() calls all move a single
-        pointer into the file, and append mode, non-blocking I/O and asynchronous
-        I/O options are shared between the references.  If a separate pointer
-        into the file is desired, a different object reference to the file must be
-        obtained by issuing an additional open(2) call.  The close-on-exec flag
-        on the new file descriptor is unset.
+	The object referenced by the descriptor does not distinguish between
+        oldfd and newfd in any way. Thus if newfd and oldfd are duplicate
+        references to an open file, read(), write() and lseek() calls all
+        move a single pointer into the file, and append mode, non-blocking
+        I/O and asynchronous I/O options are shared between the references.
+        If a separate pointer into the file is desired, a different object
+        reference to the file must be obtained by issuing an additional
+        open(2) call.
+
+        The close-on-exec flag on the new file descriptor is unset.
+
+        If oldfd is valid and has the same integer value as newfd, nothing is
+        done, and newfd is returned unchanged.
+
+        If newfd is already valid when this function is called, its old
+        descriptor is deallocated before this function returns.
+
+        This function fails gracefully if oldfd is invalid.
 
     INPUTS
 	oldfd - The file descriptor to be duplicated
-	newfd - The value of the new descriptor we want the old one to be duplicated in
+	newfd - The value of the new descriptor we want the old one to be
+            duplicated in
 
     RESULT
 	-1 for error or newfd on success
@@ -56,9 +67,9 @@
 
 ******************************************************************************/
 {
-    fdesc *oldfdesc;
-    fdesc *newfdesc;
+    fdesc *oldfdesc, *newfdesc, *oldnewfdesc;
 
+    /* Fail if old FD is invalid */
     oldfdesc = __getfdesc(oldfd);
     if (!oldfdesc)
     {
@@ -66,20 +77,34 @@
 	return -1;
     }
 
+    /* Do nothing if FDs are identical */
+    if (oldfd == newfd)
+        return newfd;
+
+    /* Keep back-up of old "newfd" */
+    oldnewfdesc = __getfdesc(newfd);
+
+    /* Allocate new FD or fail */
     newfdesc = __alloc_fdesc();
-    if(!newfdesc)
+    if (!newfdesc)
     {
 	errno = ENOMEM;
 	return -1;
     }
-    
+
+    /* Initialise new FD */
     newfdesc->fdflags = 0;
     newfdesc->fcb = oldfdesc->fcb;
-    
+
     newfd =__getfdslot(newfd);
     if (newfd != -1)
     {
 	newfdesc->fcb->opencount++;
+
+        /* Free old "newfd" (now that we've definitely succeeded) */
+        if (oldnewfdesc)
+            __free_fdesc(oldnewfdesc);
+
 	__setfdesc(newfd, newfdesc);
     }
 
-- 
2.11.4.GIT