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Subject: RE: Dynamic loading of cygwin dependent dlls
Date: Tue, 10 Aug 2004 15:49:07 -0400
Message-ID: <64AE3D5B518E3648ACC823FBCB0B737502767F2D@sr002-2kexc.ateb.com>
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From: "Reid Thompson" <Reid DOT Thompson AT ateb DOT com>
To: "Peter Ekberg" <peda AT axentia DOT se>, <cygwin AT cygwin DOT com>
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take the underscore out of the dll name

psuedo_stub -> psuedostub

reid


> -----Original Message-----
> From: Peter Ekberg [mailto:peda AT axentia DOT se] 
> Sent: Tuesday, August 10, 2004 3:11 PM
> To: cygwin AT cygwin DOT com
> Subject: Re: Dynamic loading of cygwin dependent dlls
> 
> 
> Christopher Faylor wrote:
> >On Thu, Aug 05, 2004 at 09:09:40AM +0200, Peter Ekberg wrote:
> >>I have read several messages stating that dlopen does not work for
> dlls
> >>that depend on cygwin1.dll.
> >>(e.g. http://sources.redhat.com/ml/cygwin/2004-06/msg01056.html).
> >>I have also understood that this is due to some structures 
> not being 
> >>initialized in that case.
> >>
> >>Is this dlopen problem limited to non-cygwin apps? I.e. is it true 
> >>that an app that depends directly on the cygwin1.dll is 
> incapable of 
> >>dlopening dlls that depend on cygwin1.dll?
> >
> >No, it is not true.  dlopen would be pretty worthless if it 
> didn't work 
> >in a standard cygwin program.
> 
> Indeed. Knowing that it should work, I was inspired to do 
> some more tests.
> 
> The reason I asked is that the following results in a dll 
> that can't be
> dlopened:
> 
> foo.c:
> ------------8<---------------
> __declspec(dllexport) int foo(int bar);
> 
> int foo(int bar)
> {
> 	return bar;
> }
> ------------8<---------------
> 
> Build commands:
> $ gcc -c foo.c
> $ dlltool --dllname pseudo_stubs.dll --exclude-symbols 
> DllMain AT 12,_cygwin_dll_entry AT 12,_cygwin_noncygwin_dll_entry AT 12
,DllMainCR
> TStartup AT 12,DllEntryPoint AT 12 --output-def foo.def  foo.o
> $ dllwrap --dllname pseudo_stubs.dll --output-lib 
> pseudo_stubs.dll.a --def foo.def foo.o -L/usr/lib
> 
> However, further tests have shown that if I change the name 
> pseudo_stubs to foo in the above commands, it works like a 
> charm. Like this:
> 
> $ gcc -c foo.c
> $ dlltool --dllname foo.dll --exclude-symbols 
> DllMain AT 12,_cygwin_dll_entry AT 12,_cygwin_noncygwin_dll_entry AT 12
,DllMainCR
> TStartup AT 12,DllEntryPoint AT 12 --output-def foo.def  foo.o
> $ dllwrap --dllname foo.dll --output-lib foo.dll.a --def 
> foo.def foo.o -L/usr/lib
> 
> I use this program to test whether the resulting dll works:
> 
> load.c
> ------------8<---------------
> #include <stdio.h>
> #include <dlfcn.h>
> 
> char *dlls[] = {
> 	"pseudo_stubs.dll",
> 	"foo.dll",
> 	NULL
> };
> 
> int main(void)
> { 
> 	int i;
> 	void *res;
> 	
> 	for(i=0; dlls[i]; ++i) {
> 		printf("%s\t", dlls[i]);
> 		res=dlopen(dlls[i], RTLD_LAZY | RTLD_GLOBAL);
> 		if(!res)
> 			printf("%s\n", dlerror());
> 		else
> 			printf("ok\n");
> 	}
> 
> 	return 0;
> }
> ------------8<---------------
> 
> I build load.c with "gcc load.c -o load" and ./load produces this
> output:
> pseudo_stubs.dll		dlopen: Win32 error 998
> foo.dll	ok
> 
> Any help on this would be appreciated.
> 
> Cheers,
> Peter Ekberg
> 
> 

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