Re: Using Gnat.Sockets in a Windows DLL

[ahlan@marriott.org]

On Thursday, November 26, 2015 at 8:57:02 AM UTC+1, ah...@marriott.org wrote:
> We have windows programs and DLLs that use the Windows WinSock API directly.
> In order to make this code target independent (at least for Linux & OSX) we thought we should convert the code to use Gnat.Sockets.
> This is relatively trivial.
> Or at least it is for programs.
> When we try to convert our DLLs we run into a linker problem.
> If all we do is a "with Gnat.Sockets" then using GprBuild produces lots of messages saying that various entry points could not be found.
> See below.
> I recognize many of them as being in WS2_32.dll - which GprBuild finds when we build our programs (its in Windows/System32)
> Except that the names are not quite right so I suspect that this is the root cause of the problem.
> Has anyone any idea why a build of a DLL should behave differently to a build of a program with respect to name mangling?
> 
> Best wishes,
> Ahlan
> -----------
> 
> gprbuild -d -PD:\Binary\Ada\tools\cal_dll\Cal_Dll.gpr -XWIN32ADA_BUILD=default -XLIBRARY_TYPE=static
> gprlib.exe Cal_Dll.lexch
> gnatbind -n -o b__Cal_Dll.adb -LCal_Dll -a -E D:\Binary\Ada\tools\cal_dll\objects\cal_dll_interface.ali
> gcc.exe -c -x ada -gnatA -gnatws b__cal_dll.adb -o b__cal_dll.o ...
> gcc.exe -shared -static-libgcc -o W:\product\windows\Cal_Dll.dll D:\Binary\Ada\tools\cal_dll\objects\cal_dll_interface.o ...
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socket.o):g-socket.adb:(.text+0x1b46): undefined reference to `gethostname@8'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socket.o):g-socket.adb:(.text+0x1c9c): undefined reference to `getpeername@12'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socket.o):g-socket.adb:(.text+0x2323): undefined reference to `getsockopt@20'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socket.o):g-socket.adb:(.text+0x3518): undefined reference to `getsockopt@20'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socthi.o):g-socthi.adb:(.text+0x1c): undefined reference to `WSASetLastError@4'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socthi.o):g-socthi.adb:(.text+0x246): undefined reference to `WSASetLastError@4'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(g-socthi.o):g-socthi.adb:(.text+0x27f): undefined reference to `WSASetLastError@4'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(socket.o):socket.c:(.text+0x109): undefined reference to `_imp__getservbyname@8'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(socket.o):socket.c:(.text+0x159): undefined reference to `_imp__getservbyport@8'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(socket.o):socket.c:(.text+0x2a4): undefined reference to `__WSAFDIsSet@8'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(socket.o):socket.c:(.text+0x34c): undefined reference to `_imp__ioctlsocket@12'
> C:\gnatpro\7.3.1\lib\gcc\i686-pc-mingw32\4.9.3\/adalib/libgnat.a(socket.o):socket.c:(.text+0x3b4): undefined reference to `_imp__WSAStringToAddressA@20'
> collect2.exe: error: ld returned 1 exit status
> gprlib: c:\gnatpro\7.3.1\bin\gcc execution error
> gprbuild: could not build library for project cal_dll
> [2015-11-26 08:36:34] process exited with status 4, 100% (36/36), elapsed time: 01.67s

If I have a one line test program that merely initialises a socket, ie

  My_Socket : GNAT.Sockets.Socket_Type;
begin
  GNAT.Sockets.Create_Socket (My_Socket);

then we have no problems building an executable but if we try and use the same
lines in a DLL we fail to find the external references.
Even if I explicitly put "Pragma Linker_Options ("-lws2_32");
and place libws2_32.a in the Library_Dir Gnat still fails to satisfy the references.

I am at a loss as to what I might be doing wrong and what I could try next.
This should be easy to solve, it probably has nothing to do with Gnat Sockets
but more to do with building DLLs using a GPR file.

The following is our Gpr file
with "gtkada";
with "win32ada";

project Monitor is

   package Naming is
      for Casing use "mixedcase";
   end Naming;

   for Library_Name use "Monitor";
   for Shared_Library_Prefix use "";

   for Source_Dirs use ("w:\source\ada\interfaces\monitor",
                        "w:\source\ada\interfaces",
                        "w:\source\ada\shared",
                        "w:\source\ada\open\shared");

   for Library_Interface use ("Monitor_Interface");

   for Object_Dir use "objects";

   for Library_Options use ("-Lw:\product\windows", "resources.o");
   for Library_Dir use "w:\product\windows";
   for Library_Ali_Dir use "d:\binary\ada\interfaces\monitor";
   for Library_Kind use "dynamic";
   for Library_Standalone use "encapsulated";

   package Pretty_Printer is
      for Default_Switches ("ada") use ("-i2", "-M120", "-aL", "-A1", "-A4");
   end Pretty_Printer;

   package Builder is
      for Default_Switches ("ada") use ("-s", "-g");
   end Builder;

   package Compiler is
      for Default_Switches ("ada") use ("-O1", "-gnatQ", "-gnato", "-g", "-gnat12",
                                        "-gnatwcehijkmopruvz.c.n.p.t.w.x", "-gnatykmpM120");
   end Compiler;

   package Binder is
      for Default_Switches ("ada") use ("-E");
   end Binder;




We build are DLLs using Gprbuild.
I