[XFree86-4.2.0] Now that we have an improved ld, please make libXt a shared library.

[Alexander Gottwald]

Ralf Habacker wrote:

> Hi Alexander,
>
> >
> > for libXt it uses the direct address. For every other library using
> > the libXt.dll it uses the address from the stub.
>
> I see, this is another case. Please take a look into xc/lib/xt/Initialize.c and
> xc/lib/xt/sharedlib.c which provides such a case for another os. I don't
> understand the xfree build system very well, so I can't provide a working
> solution for this, but in fact _XtInherit() should be located in the xt import
> library, which references __XtInherit() which is located in the real xt dll.

I played with this too.

What we need is a possibility to
 - link libXt that _XtInherit is taken from the import lib
   -> impossible (AFAIK). The import lib is created _after_ all symbols got
      resolved (hen-egg-problem)
 - use everywhere the same pointer. The shared lib could get the pointer via
   a function call.

   typedef void (*func)(void);
   func  __XtInheritFunc() { return _XtInherit(); }
   #define _XtInherit __XtInheritFunc()

   This works until someone uses

   struct x {
       func foo = _XtInherit;
   }

   The linker would normally resolve the symbol. But with the function call
   we have a situation where the static structure requires a dynamic call.

Maybe I've missed something. But it seems to me that

 we need the real address of _XtInherit at linktime which is not known to
 the linker when building the shared library because libXt might get
 relocated.

I've found a working solution

--test.h--
typedef void (*func)(void);
extern func f;
extern int test(func f);
extern int test1(void);
extern int test2(void);
--test1.c--
#include "test.h"
#include <stdio.h>

void __f(void) { printf("f\n"); return; }
func f = __f;

int test(func f2) { return f == f2; }
int test1(void) { f(); return test(f); }
--test2.c--
#include "test.h"
#include <stdio.h>

int test2(void) { f(); return test(f); }
int main() {
        printf("test1: %d\n", test1());
        printf("test2: %d\n", test2());
}
----------

$ gcc --shared -out-implib=test1.dll.a -Wl,--enable-auto-import,--enable-runtime-pseudo-reloc -o test1.dll test1.c
Creating library file: test1.dll.a
$ gcc -o test2.exe test2.c test1.dll test1.dll.a
Info: resolving _f by linking to __imp__f (auto-import)
$ ./test2.exe
f
test1: 1
f
test2: 1

I'll try this with libXt

bye
    ago

NP: Deine Lakaien - Return
-- 
 Alexander.Gottwald@informatik.tu-chemnitz.de
 http://www.gotti.org           ICQ: 126018723