Message-ID: <4AF0E721.8000102@users.sourceforge.net>
Date: Tue, 03 Nov 2009 20:29:53 -0600
From: "Yaakov (Cygwin/X)" <yselkowitz AT users DOT sourceforge DOT net>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.4pre) Gecko/20090915 Thunderbird/3.0b4
MIME-Version: 1.0
To: cygwin AT cygwin DOT com
Subject: binutils: dlltool DATA exports incompatible with auto-import
Content-Type: multipart/mixed;  boundary="------------050201050905050707060801"
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com

--------------050201050905050707060801
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

GNOME Evolution contains several interdependent libraries, so on 
Cygwin/MinGW the build creates artificial import libraries with dlltool 
from .def files.  While trying to build 2.28 I came across a possible 
incompatibility between the implib generated by dlltool and auto-import 
linkage:

$ gcc -shared -Wl,--out-implib,libtest.dll.a -o cygtest.dll libtest.c
Creating library file: libtest.dll.a

$ nm libtest.dll.a | grep -v ' [bdit] '

d000003.o:
00000000 I _cygtest_dll_iname

d000000.o:
00000000 I __head_cygtest_dll
          U _cygtest_dll_iname

d000002.o:
          U __head_cygtest_dll
00000000 I __imp__test_func
00000000 T _test_func

d000001.o:
          U __head_cygtest_dll
00000000 I __imp__test_data
00000000 I __nm__test_data

$ gcc -o test.exe test.c libtest.dll.a

# now let's try with dlltool
$ dlltool --dllname cygtest.dll --input-def libtest.def --output-lib 
libtest.dll.a

$ nm libtest.dll.a | grep -v ' [bdit] '

deobt.o:
00000000 I __libtest_dll_a_iname

deobh.o:
00000000 I __head_libtest_dll_a
          U __libtest_dll_a_iname

deobs00001.o:
          U __head_libtest_dll_a
00000000 I __imp__test_func
00000000 T _test_func

deobs00000.o:
          U __head_libtest_dll_a
00000000 I __imp__test_data
# Note no __nm__test_data auto-import here

$ gcc -o test.exe test.c libtest.dll.a
fu000001.o:(.idata$2+0xc): undefined reference to `_libtest_dll_a_iname'
nmth000000.o:(.idata$4+0x0): undefined reference to `__nm__test_data'
collect2: ld returned 1 exit status


Yaakov

--------------050201050905050707060801
Content-Type: text/plain;
 name="libtest.c"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="libtest.c"

__declspec(dllexport) int test_data = 42;
__declspec(dllexport) int test_func(void) { return test_data; }

--------------050201050905050707060801
Content-Type: text/plain;
 name="libtest.def"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="libtest.def"

EXPORTS
test_func
test_data DATA

--------------050201050905050707060801
Content-Type: text/plain;
 name="test.c"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="test.c"

extern int test_data;
extern int test_func(void);

int
main(void) {
	int foo = test_data;
	test_func();
	return 0;
}


--------------050201050905050707060801
Content-Type: text/plain; charset=us-ascii

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
--------------050201050905050707060801--