Re: [Mingw-users] Exporting functions from EXEs

[José F. <j_r...@ya...>]

On 2002.05.09 08:41 Luke Dunstan wrote:
> 
> ----- Original Message -----
> From: "Daniel Grace" <ru...@ea...>
> To: <min...@li...>
> Sent: Thursday, May 09, 2002 8:10 AM
> Subject: Re: [Mingw-users] Exporting functions from EXEs
> 
> 
> >
> > From: "José Fonseca" <j_r...@ya...>
> > To: <min...@li...>
> > -- snip --
> > >
> > > Check http://www.mingw.org/docs.shtml for more information about
> building
> > > DLLs on MinGW.
> > >
> > -- snip --
> > > Replacing the EXE target command
> > >
> > > > gcc  agent.o common.o  cfg.o dlgcfg.o dlgcon.o gw.o lrapi.o
> lrapisup.o
> > > > notify.o numonly.o tags.o
> dialogs.ro  -mwindows -ldbuf -lwsock32 -Wl,-E
> > > > -o lragent.exe
> > >
> > > for
> > >
> > >    dllwrap  agent.o common.o  cfg.o dlgcfg.o dlgcon.o gw.o lrapi.o
> > > lrapisup.o
> > >    notify.o numonly.o tags.o
> dialogs.ro  -mwindows -ldbuf -lwsock32 -Wl,-E
> > >    -o lragent.exe
> > >
> > > or
> > >
> > >    gcc -shared agent.o common.o  cfg.o dlgcfg.o dlgcon.o gw.o lrapi.o
> > > lrapisup.o
> > >    notify.o numonly.o tags.o
> dialogs.ro  -mwindows -ldbuf -lwsock32 -Wl,-E
> > >    -o lragent.exe
> > >
> > > should do the trick.
> > >
> > > José Fonseca
> > >
> >
> > Along with following the instructions at the aforementioned website,
> I've
> > tried both of those and neither of them work. While they compile and
> link
> > correctly, the end result isn't executable (it seems to simply be a DLL
> with
> > an EXE extension) -- I'm left with the same problem I had when I
> > used -shared earlier.
> 
> Yes I think you are right that the command Jose gave just creates a DLL
> with
> a .exe extension. Some reasons why this isn't working may be:
> 
> (1) The linker sets a flag in the executable's header to indicate that it
> is
> a DLL.
> (2) The wrong entry point (DllMain) will be used, and the wrong startup
> code
> will be linked (dllcrt.o ?)
> (3) Other settings like the base address are changed.
> 

Since DLL and EXE have exactly the same format (PE) I thought that this 
would work. (3) is not important but (1) and (2) might affect the 
genereation.

> I think the reason why compiling normally as an EXE doesn't work is
> because
> no export section (.edata) will be created by the linker. I haven't tried
> this, and I don't have an exact solution but I have a feeling that using
> "dlltool --output-exp" to create the exports section (which is just a
> special *.o file I think) and linking this with "gcc -o foo.exe *.o
> foo.exp"
> might work.
> 

If this doesn't work then you'll shurely need to read the dllhelpers 
(available from Mumit Khan's site) README, which explain the steps made by 
dllwrap to build a DLL (or alternatively run "dllwrap --dry-run -o foo.exe 
*.o") - it's basically a series of calls to "gcc" and "dlltool" to 
generate the exports, and adapt to generate an exe, i.e., remove the 
"--dll" flag.

José Fonseca