Suppressing linking errors with GCC/G++/ld under Cygwin

[Gerrit P. Haase]

Robert McLeay wrote:

> Hi,
> 
> (Sorry if this is OT, I'm trying to find out the Cygwin equivalent of
> a GCC flag from other platforms.)
> 
> I'm trying to compile a library for Qu-Prolog that will be linked at
> run-time with program internals. As it will be linked at run time, I
> would like to suppress all "undefined reference" errors somewhat
> similarly to using "-undefined suppress" under Mac OS X.
> 
> I'm using Cygwin, and here is the error message and the g++ line that I
> am using.
> 
> rob@ches-laptop /cygdrive/c/rand2
> 
> $ g++ -shared -Wl,-soname,sym001476 $RAND2_LIB/rand.o  -lc -o sym001476
> 
> ../rand.o(.text+0x24f): In function `iunif_interface':
>    /    cygdrive/c/rand2/rand.cc:79: undefined reference to
> `Thread::unify(Object*, Object*, bool)'
> ../rand.o(.text+0x2ce): In function `iunif_interface':
>    /    cygdrive/c/qp-cygwin-withicm/src/heap_qp.h:278: undefined reference to
> `Heap::outOfSpace()'
> collect2: ld returned 1 exit status
> 
> Is there any way to suppress these errors and let it compile under
> Cygwin the same way as using "g++ -flat_namespace -undefined suppress
> -bundle" would under Mac OS X?

It is not possible to link a shared module / DLL or executable with
undefined references on Windows / Cygwin and so there is no switch to
enable this.  Symbols must resolve at link time.  If you need symbols
in a shared library then create and link against an importlib, if
symbols from an executable are needed then you try to figure out how to
create the executable so it exports these symbols, then create an import
library for these symbols and link against this importlib so the linker
is able to resolve the references at linktime.

Gerrit
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