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Subject: RE: Dynamic loading of cygwin dependent dlls
Date: Tue, 10 Aug 2004 15:56:38 -0400
Message-ID: <64AE3D5B518E3648ACC823FBCB0B737502767F2E@sr002-2kexc.ateb.com>
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From: "Reid Thompson" <Reid DOT Thompson AT ateb DOT com>
To: "Reid Thompson" <Reid DOT Thompson AT ateb DOT com>, "Peter Ekberg" <peda AT axentia DOT se>,
   <cygwin AT cygwin DOT com>
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actually -- that's not it, as this code, gives the following results:

CODE-----------CODE
#include <stdio.h>
#include <dlfcn.h>

char *dlls[] = {
	"pseudostubs.dll",
	"foo.dll",
	"psuedostubs.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;
}
RESULTS-------------RESULTS
pseudostubs.dll dlopen: Win32 error 126
foo.dll ok
psuedostubs.dll ok

reid


> -----Original Message-----
> From: Reid Thompson 
> Sent: Tuesday, August 10, 2004 3:49 PM
> To: Peter Ekberg; cygwin AT cygwin DOT com
> Subject: RE: Dynamic loading of cygwin dependent dlls
> 
> 
> 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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