[ENet-discuss] eNet and valgrind.

[Espen Overaae]

Valgrind is giving me these warnings:

==26393== Syscall param socketcall.sendmsg(msg.msg_name) points to
uninitialised byte(s)
==26393==    at 0x4B3138B: (within /lib64/libpthread-2.5.so)
==26393==    by 0x4C5299C: enet_socket_send (unix.c:284)
==26393==    by 0x4C5208A: enet_protocol_send_outgoing_commands
(protocol.c:1406)
==26393==    by 0x4C52308: enet_host_service (protocol.c:1528)

==26393== Syscall param socketcall.sendmsg(msg.msg_name) points to
uninitialised byte(s)
==26393==    at 0x4B3138B: (within /lib64/libpthread-2.5.so)
==26393==    by 0x4C5299C: enet_socket_send (unix.c:284)
==26393==    by 0x4C5208A: enet_protocol_send_outgoing_commands
(protocol.c:1406)
==26393==    by 0x4C5227F: enet_host_service (protocol.c:1500)

==26393== Syscall param socketcall.sendmsg(msg.msg_name) points to
uninitialised byte(s)
==26393==    at 0x4B3138B: (within /lib64/libpthread-2.5.so)
==26393==    by 0x4C5299C: enet_socket_send (unix.c:284)
==26393==    by 0x4C5208A: enet_protocol_send_outgoing_commands
(protocol.c:1406)
==26393==    by 0x4C52118: enet_host_flush (protocol.c:1428)

After investigating the cause, it seems the variable sin, used in
        msgHdr.msg_name = & sin; at enet_socket_send (unix.c:281)
is the culprit.

http://beej.us/guide/bgnet/output/html/multipage/sockaddr_inman.html
has this to say about it:
> #include <netinet/in.h>
>
> struct sockaddr_in {
>     short            sin_family;   // e.g. AF_INET
>     unsigned short   sin_port;     // e.g. htons(3490)
>     struct in_addr   sin_addr;     // see struct in_addr, below
>     char             sin_zero[8];  // zero this if you want to
> };
>
> struct in_addr {
>     unsigned long s_addr;  // load with inet_aton()
> };

and especially:
> There's also this sin_zero field which some people claim must be set to zero.
> Other people don't claim anything about it (the Linux documentation doesn't
> even mention it at all), and setting it to zero doesn't seem to be actually
> necessary. So, if you feel like it, set it to zero using memset().

Setting sin.sin_zero to zero makes the problem go away.


Espen Overaae