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From: "Ivan Warren" <ivan AT vmfacility DOT fr>
To: <cygwin AT cygwin DOT com>
Subject: Library strip, automatic imports and specific imports
Date: Wed, 17 Sep 2003 11:11:22 +0200
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Hello,

First of all, my apologies if this isssue has already been addressed. I
searched the archive but couldn't find anything relevant.

I am running into the following problem :

If I issue a 'strip --strip-unneeded' to a DLL import library (created with
--out-implib), Most .data and/or .bss external references generate linking
errors.

Furthermore, if I specify a __declspec(dllimport) to the reference *AND* the
symbol is referenced by a DLL itself, the application raises SIGSEGV upon
attempting to access the symbol.

I am not sure binary attachments are allowed on this list, so here is a copy
& paste of the files necessary to reproduce the problem :

(note : the Makefile should have the spaces changed to a tab character)

<sample>
<File fn="Makefile">
maincode: maincode.o libmydll.dll.a
        $(CC) $(CFLAGS) -o maincode maincode.o -L. -lmydll

libmydll.dll.a: dllcode.o libmydll2.dll.a
        $(CC) dllcode.o -o cygmydll.dll -shared -L. -lmydll2
-Wl,--out-implib -Wl,libmydll.dll.a
        strip --strip-unneeded libmydll.dll.a

libmydll2.dll.a: dllcode2.o
        $(CC) dllcode2.o -o cygmydll2.dll -shared -Wl,--out-implib
-Wl,libmydll2.dll.a
        strip --strip-unneeded libmydll2.dll.a

clean:
        rm -f *.o
        rm -f *.a
        rm -f *.dll
        rm -f *.exe
        rm -f *.stackdump
</File>
<File fn="dllcode.c">
extern __declspec(dllimport) level2;
int somebss;
int somedata=2;
int sometext()
{
    return(level2);
}
</File>
<File fn="dllcode2.c">
__declspec(dllexport) int level2=1;
</File>
<File fn="maincode.c">
extern __declspec(dllimport) int somebss;
extern __declspec(dllimport) int somedata;
extern __declspec(dllimport) int sometext();
int main()
{
    printf("%d\n",somebss);
    printf("%d\n",somedata);
    printf("%d\n",sometext());
}
</File>
</sample>

If you run './maincode' after make, the programs crashes.

If you remove '__declspec(dllimport) from file 'dllcode.c' the link fails.

If you comment out the 'strip' from the Makefile, the program links AND runs
to completion.

My questions is :

Is this a 'binutil' core issue or something introduced by cygwin ?
Is there a workaround (besides NOT stripping the import library) ?

Note : this issues is a main concern when using 'libtool' because this
behaviour is shown when using a libtool in confunction with
automake/autoconf and a 'make install-strip' is issued.

Thanks,

--Ivan


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