Re: nasty link problem with Gfortran and G++ (C++) ???

On 1/7/2025 4:18 PM, Thomas Koenig wrote:

Lynn McGuire <lynnmcguire5@gmail.com> schrieb:

I just ran into a nasty problem with GFortran and G++ (C++).  Probably
not a bug ???  I am using GCC 14.1.
>
I have a lot of code in C++ (over 100,000 lines).  I have 750,000 lines
of code in GFortran.  I have to extern "C" this code in C++ to make it
callable by GFortran code.
>
I missed declaring a couple of C++ functions as extern "C" which means
that they kept their C++ mangled link names.  But these C++ functions
were declared as integer*8 and external in the GFortran code (old F77
code).
>
So, the GCC linker did not report to me that it did not have a link for
the G++ functions.  This may be a bug, I am not sure.

 Without having looked at the source code, I suspect
it is probably something that you are not describing.
 You can look into the object files with any number of utilities,
for example "nm".  Here's an example:
 subroutine foo
   external bar
   integer *8 bar
   print *,bar(1234)
end subroutine foo
 Compiling to an object file and running nm on this will show you
                   U bar_
0000000000000000 T foo_
                  U _gfortran_st_write
                  U _gfortran_st_write_done
                  U _gfortran_transfer_integer_write
 which means you have a symbol "foo_" defined, it is a global (hence
uppercase) symbol in the text section (hence T).  You also have
several undefined symbols, among them bar_, plus some gfortran
library routines, so all is fine.
 If you do not find your undefined

When I ran the program, the C++ functions were not called by the
GFortran code.  Instead, the GFortran code treated the C++ functions as
integer*8 scalar variables.

 

>
If needful, I can probably put together a small code sample that
exhibits the problem.  Maybe.  It could be that the size of my code
affects the GCC linker.

 That I would consider highly unlikely.

I cannot get a small code sample with or without a DLL to exhibit the problem.  Like I said, I thought it was something related to size of my DLL.  And this is the small DLL, only 3 MB.
Thanks,
Lynn