Re: GNAT, Windsock, and DLLs

["Barry Scott" <cbscott__@ingr.com>]

I'm not sure it matters for your code, but the dll is winsock.dll, not
windsock.dll.
Barry

Do-While Jones wrote in message <6gvp5f$evp$1@owens.ridgecrest.ca.us>...
>The general question is, "How does GNAT link Ada 95 programs with Windows
>95 DLLs?"
>
>More specifically, "How can GNAT make use of the Berkeley-like socket
>services in windsock.dll?"
>
>In particular, "What do I need to do to get a demo program (included at
>the end of this message) to call the gethostname service in windsock.dll?"
>
>Background
>
>Several years ago, I wrote a collection of Network Interface packages
>which allow Ada 83 programs (compiled using the Telesoft Telegen 2
>compiler on a Sun Sparcstation 2) to call the Berkeley BSD socket
>routines.  These thick bindings gave me handy abstractions that send and
>receive UDP broadcasts, and implement TCP/IP clients and servers.
>
>A couple years ago I ported these packages from our Sun workstations to
>GNAT (Ada 95) on Silicon Graphics in no time at all.  This was easily done
>because the Silicon Graphics was using a UNIX operating systems with
>Berkeley sockets.
>
>A few months ago I tried to port these same packages to GNAT (Version
>3.10) on a Windows 95 machine.  Windows 95 comes with a dynamically linked
>library (DLL) called windsock, which emulates all the Berkeley socket
>services.  One of the simplest of these is gethostname, which returns a
>character string containing the name of the host computer.
>
>The Problem
>
>Use gnatchop to divide the program at the end of this message into three
>compilation units.  Then use gnatmake to compile and link ni09td01.
>(Network Interfaces, component 9, Test Demo program 1.) The program
>compiles, but fails at the link stage with an error message that says
>there is an "undefined reference to 'gethostname' in get_host.adb".
>Clearly, GNAT doesn't know about the gethostname service in windsock.dll.
>
>The GNAT UserUs Guide section on "Search Paths for gnatbind" (yes, I'm one
>of those few people who read the documentation) says that you can tell the
>linker to look for modules in other directories in several ways.  One of
>these ways is to set the environment variable ADA_OBJECTS_PATH.  So, I set
>ADA_OBJECTS_PATH to "C:\WINDOWS\SYSTEM" where the windsock.dll is (on my
>system, at least). That didn't work.
>
>I suspect gnatbind is looking for a ".o" file, not a ".dll" file.
>
>I know very little about C, and even less about Windows 95.  I suspect
>this problem is more of a C/Windows 95 problem than an Ada problem.
>
>What is the solution?
>
>Do I have to write a zillion (well, actually eight, since I only use
>socket, bind, accept, fcntrl, open, close, read, write, and gethostname)
>little C programs that call each windsock service individually, and put
>their ".o" files somewhere that GNAT can find them?  Is there a way to get
>GNAT to use the windsock.dll directly?
>
>If there is a simple solution, I'm sure many readers of Comp.lang.ada
>would find it useful.
>
>Thanks in advance,
>
>Do-While Jones
>-------------------------------------------------------------
>
>--                      ni09ks01.ada
>--                      13 December 1994
>
>--                      Do-While Jones
>--                      324 Traci Lane
>--                      Ridgecrest, CA 93555
>--                      do_while@ridgecrest.ca.us
>
>--with NETWORK;  -- part NI02
>
>package GET_HOST is
>
>  function Name return string;
>    -- Tells you the name of the computer that is executing
>    -- the program.
>
>  --function Network_Address return NETWORK.Address_numbers;
>    -- Tells you the network address  of the computer that
>    -- is executing the program.
>
>end GET_HOST;
>
>--                      ni09kb01.ada
>--                      13 December 1994
>
>--                      Do-While Jones
>--                      324 Traci Lane
>--                      Ridgecrest, CA 93555
>--                      do_while@ridgecrest.ca.us
>
>with SYSTEM;
>
>package body GET_HOST is
>
>  --- Interface to UNIX service ---
>
>  function gethostname(
>    name_receiver : SYSTEM.Address;
>    namelen       : integer)
>    return integer;
>  pragma Interface(C, gethostname);
>
>  ---------------------------------
>
>  function Name return string is
>    -- Assume the name will be 20 characters
>    -- or less.
>    C_STRING : string(1..21)
>      := (others => ASCII.NUL);
>    UNIX_RESULT : integer;
>    LENGTH      : integer;
>  begin
>    -- Call a UNIX service to put the name
>    -- in C_STRING.
>    UNIX_RESULT := gethostname(
>      C_STRING(1)'ADDRESS, C_STRING'LENGTH);
>    if UNIX_RESULT /= 0 then
>      -- UNIX failure.
>      return "HOST_NAME_ERROR";
>    end if;
>
>    -- Find out how long the string is.
>    LENGTH := 0;
>    for i in C_STRING'RANGE loop
>      exit when C_STRING(i) = ASCII.NUL;
>      LENGTH := i;
>    end loop;
>
>    -- Return the non-null characters of the string.
>    return C_STRING(1..LENGTH);
>  end Name;
>
>  --function Network_Address
>    --return NETWORK.Address_numbers is
>  --begin
>    --return NETWORK.Host_Number(Name);
>  --end Network_Address;
>
>end GET_HOST;
>
>--                      ni09td01.ada
>--                      13 December 1994
>
>--                      Do-While Jones
>--                      324 Traci Lane
>--                      Ridgecrest, CA 93555
>--                      do_while@ridgecrest.ca.us
>
>with TEXT_IO,
>     --NETWORK,   -- part NI02
>     GET_HOST;  -- part NI09
>
>procedure NI09TD01 is
>begin
>  TEXT_IO.Put_Line("This machine is "
>    & GET_HOST.Name & ".");
>  --TEXT_IO.Put_Line("It is at address "
>    --& NETWORK.Image(GET_HOST.Network_Address)
>    --& ".");
>end NI09TD01;
>
>