[FFmpeg-devel] [PATCH] adding _GNU_SOURCE for udp.c compilation

[Rich Felker]

On Sun, Feb 10, 2008 at 09:14:42PM -0500, Rich Felker wrote:
> On Sun, Feb 10, 2008 at 07:20:31PM +0100, Nicolas George wrote:
> > Hi.
> > 
> > Le duodi 22 pluvi?se, an CCXVI, Reimar D?ffinger a ?crit?:
> > > Well in my header file (gentoo and debian) they are claimed to be part of
> > > POSIX1.g, so they are not under a GNU ifdef.
> > > Though I admit I could not find it in the POSIX specs I had lying
> > > around.
> > 
> > Neither NI_MAXSERV nor NI_MAXHOST appear in the Single Unix Specification
> > version 3, which is a superset of POSIX.
> > 
> > http://sources.redhat.com/cgi-bin/cvsweb.cgi/libc/resolv/netdb.h?annotate=1.47.2.1&cvsroot=glibc
> > 
> > shows that the check for _GNU_SOURCE has been added three weeks ago, with
> > the log message "Cleanup namespace.".
> > 
> > getnameinfo seems to return EAI_OVERFLOW if the buffers are not big enough.
> > EAI_OVERFLOW is standard, and described in the SUSv3 about netdb.h, but not
> > referenced in the page about getnameinfo.
> > 
> > I fear that the only absolutely reliable way of doing this is to increase
> > dynamically the buffer each time EAI_OVERFLOW is returned. Yet, using
> > NI_MAX* when they are defined as the initial size for the buffer should be
> > helpful nonetheless.
> 
> For the service number (port), sizeof(int)*3 is a perfectly acceptable
> bound. This function does not even make use of the hbuf result so it
> should be passing a null pointer for that rather than wasting
> complexity and stack space.

And here is the patch.

Rich
-------------- next part --------------
Index: libavformat/udp.c
===================================================================
--- libavformat/udp.c	(revision 11901)
+++ libavformat/udp.c	(working copy)
@@ -196,10 +196,9 @@
 
 static int udp_port(struct sockaddr_storage *addr, int addr_len)
 {
-    char sbuf[NI_MAXSERV];
-    char hbuf[NI_MAXHOST];
+    char sbuf[sizeof(int)*3+1];
 
-    if (getnameinfo((struct sockaddr *)addr, addr_len, hbuf, sizeof(hbuf),  sbuf, sizeof(sbuf), NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
+    if (getnameinfo((struct sockaddr *)addr, addr_len, NULL, 0,  sbuf, sizeof(sbuf), NI_NUMERICSERV) != 0) {
         av_log(NULL, AV_LOG_ERROR, "getnameinfo: %s\n", strerror(errno));
         return -1;
     }