[PATCH] Fix two bugs in the limit of large numbers of sockets:

[Jon Turney]

On 07/11/2017 13:44, Erik M. Bray wrote:
> * Fix the maximum number of sockets allowed in the session to 2048,
>    instead of making it relative to sizeof(wsa_event).
> 
>    The original choice of 2048 was in order to fit the wsa_events array
>    in the .cygwin_dll_common shared section, but there is still enough
>    room to grow there to have 2048 sockets on 64-bit as well.
> 
> * Return an error and set errno=ENOBUF if a socket can't be created
>    due to this limit being reached.
> ---
>   winsup/cygwin/fhandler_socket.cc | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/winsup/cygwin/fhandler_socket.cc b/winsup/cygwin/fhandler_socket.cc
> index 7a6dbdc..b8eda57 100644
> --- a/winsup/cygwin/fhandler_socket.cc
> +++ b/winsup/cygwin/fhandler_socket.cc
> @@ -496,7 +496,7 @@ fhandler_socket::af_local_set_secret (char *buf)
>   /* Maximum number of concurrently opened sockets from all Cygwin processes
>      per session.  Note that shared sockets (through dup/fork/exec) are
>      counted as one socket. */
> -#define NUM_SOCKS       (32768 / sizeof (wsa_event))
> +#define NUM_SOCKS       ((unsigned int) 2048)
>   
>   #define LOCK_EVENTS	\
>     if (wsock_mtx && \
> @@ -623,7 +623,14 @@ fhandler_socket::init_events ()
>         NtClose (wsock_mtx);
>         return false;
>       }
> -  wsock_events = search_wsa_event_slot (new_serial_number);
> +  if (!(wsock_events = search_wsa_event_slot (new_serial_number)));

This has a stray ';' at the end of the line

../../../../winsup/cygwin/fhandler_socket.cc: In member function 'bool 
fhandler_socket::init_events()':
../../../../winsup/cygwin/fhandler_socket.cc:626:3: error: this 'if' 
clause does not guard... [-Werror=misleading-indentation]
    if (!(wsock_events = search_wsa_event_slot (new_serial_number)));
    ^~
../../../../winsup/cygwin/fhandler_socket.cc:627:5: note: ...this 
statement, but the latter is misleadingly indented as if it is guarded 
by the 'if'
      {
      ^

> +    {
> +      set_errno (ENOBUFS);
> +      NtClose (wsock_evt);
> +      NtClose (wsock_mtx);
> +      return false;
> +    }
> +
>     /* sock type not yet set here. */
>     if (pc.dev == FH_UDP || pc.dev == FH_DGRAM)
>       wsock_events->events = FD_WRITE;
> 

How did you test this?