Re: Using Gnat.Sockets in a Windows DLL

[ahlan.marriott@gmail.com]

On Wednesday, 20 April 2016 19:11:09 UTC+2, Dmitry A. Kazakov  wrote:
> On 2016-01-13 21:25, ahlan.marriott@gmail.com wrote:
> > On Thursday, 26 November 2015 08:57:02 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
> >
> > Dear all,
> >
> > It seems that this is an known problem.
> > At least to AdaCore.
> > They document it as KP-22-O331-001
> > The problem is fixed in GprBuild v2.2.2 that is part of Gnat Pro 7.3.2
> > Otherwise the workaround is not to produce an encapsulated DLL but
> > to  produce a standard DLL and link in the static version of the Gnat
> > runtime using Library_options.
> > A standard DLL will link WS2_32 and linking in the static runtime will produce a standalone DLL.
> 
> I built the latest grpbuild from Git sources (not easy under Windows). 
> The problem with encapsulated library projects persists.
> 
> Presently I believe it is related to the order in which libraries 
> wsock32 and ws2_32 appear in the linker's command like. From what I read 
> researching the issue, for some mysterious reasons, -lws2_32 -lwsock32 
> must appear *before* -shared -static-libgcc. So the linker line must 
> look like:
> 
> gcc.exe -lws2_32 -lwsock32 -shared -static-libgcc -o W:\product...
> 
> There is "Leading_Library_Option" project attribute, but it is no help 
> because it does not bring its content right after gcc.exe.
> 
> Any ideas how to do it otherwise?
> 
> For example, a very crude way would to write an application 
> my_gcc_wrapper that calls gcc with -lws2_32 -lwsock32 preceding all 
> other switches and replace
> 
> package Linker is
>     for Driver ("Ada") use "my_gcc_wrapper.exe";
> end Linker;
> 
> -- 
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de

Dear Dmitry,
This does indeed solve the problem.
However the problem is not in Gprbuild.exe but in libexec/gprbuild/gprlib.exe
Have you tried building that from the latest git sources?

MfG
Ahlan