Re: creating dll to link with delphi program

[Brad Finney <brad dot finney at humboldt dot edu>]

On 10/23/2011 12:33 PM, Steve Kargl wrote:
> On Sun, Oct 23, 2011 at 11:57:32AM -0700, Brad Finney wrote:
> > > foo and bar are identical except for explicitly namng foo
> > > as Foo in the bind() expression.  Note case is preserved and
> > > there is no trailing underscore.
> >
> > Yes, I did try his suggestion, but missed the addition of the bind(c,
> > name= " ").  Thanks for getting me to read more carefully!  That does
> > correct the case issue, but not (for me) the underscore issue, which is
> > very puzzling.  I took the exact code you listed and got a leading
> > underscore on Foo and bar.
>
> I don't do Windows, so my code did not include
>
> !GCC$ ATTRIBUTES DLLEXPORT::Foo

I had already tried adding those, but it made no difference.
> > F:\FlowReader>gfortran -shared -o foo.dll foo.o
> > Cannot export Foo: symbol not found
> > Cannot export bar_: symbol not found
> > collect2.exe: error: ld returned 1 exit status
> >
> > F:\FlowReader>gfortran -shared -fno-leading-underscore -o foo.dll foo.o
> > Cannot export Foo: symbol not found
> > Cannot export bar_: symbol not found
> > collect2.exe: error: ld returned 1 exit status
>
> These are loader errors.  I'm not familiar with how the loader
> on Windows works.  As Tobias noted, you might need to add the
> stdcall attribute, but I thought that only dealt with who was
> responsible for cleaning up the call stack.

I had also tried adding stdcall.  No difference.

I can actually solve the symbol not found problem by passing the 
no-leading-underscore directly to the linker

F:\FlowReader>gfortran -fno-leading-underscore -c foo.f90
F:\FlowReader>gfortran -shared -Xlinker --no-leading-underscore -o 
foo.dll foo.o

however if I add a write statement to the subroutine

subroutine foo(n) bind(c, name="Foo")
  use iso_c_binding
!GCC$ ATTRIBUTES DLLEXPORT::Foo
  integer(c_int) :: n
  n = n + n
  write(*,*)n
end subroutine foo

and repeat the above compilation and link commands I get undefined 
refererces to library routines

F:\FlowReader>gfortran -fno-leading-underscore -c foo.f90
F:\FlowReader>gfortran -shared -Xlinker --no-leading-underscore -o 
foo.dll foo.o
foo.o:foo.f90:(.text+0x4c): undefined reference to `_gfortran_st_write'
foo.o:foo.f90:(.text+0x69): undefined reference to 
`_gfortran_transfer_integer_write'
foo.o:foo.f90:(.text+0x77): undefined reference to `_gfortran_st_write_done'
collect2.exe: error: ld returned 1 exit status


Very strange and frustrating....