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Message-ID: <3978AC2E.7145C717@ece.gatech.edu>
Date: Fri, 21 Jul 2000 16:01:50 -0400
From: Charles Wilson <cwilson AT ece DOT gatech DOT edu>
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To: Danny Smith <danny_r_smith AT hotmail DOT com>, cygwin AT sources DOT redhat DOT com
Subject: Re: binutils prerelease available for testing (feedback needed)
References: <20000721062628 DOT 85462 DOT qmail AT hotmail DOT com> <3978840D DOT 7740F581 AT ece DOT gatech DOT edu>
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OK!

The problems that I have been seeing must be related to my *overly
complex* testing -- I can only figure there's something in one of my
hacked up libpng .c or .h files that I am overlooking, since I did have
to *hack* libpng so that it would export a data item.

The following tests were done using binutils from CVS 20000721 + Mark
E.'s patch

I downloaded Mumit's dllhelpers, and built the .c version *by hand*
using 'gcc -shared' and this .def file:

EXPORTS
	dll_double_square @ 1 ; 
	dll_float_square @ 2 ; 
	dll_get_global_int_var @ 3 ; 
	dll_global_int_var @ 4 DATA ; 
	dll_int_square @ 5 ; 
	dll_set_global_int_var @ 6 ; 

I even *omitted* the dllinit.o file from the dll, so as to force cygwin
to use the built-in dllinit methods.

Build dll:
gcc -c -DBUILDING_DLL=1 -I. -g -Wall - cdll.o cdll.c
gcc -shared -Wl,--out-implib=libcdll.dll.a -Wl,--enable-auto-image-base
-o libcdll.dll cdll.def cdll.o

Build exec's:
gcc -c -I. -g -Wall -o usedll.o usedll.c

CASE 3 (use import lib)
ld -Bdynamic -o usedll-imp.exe /usr/lib/crt0.o -L./
-L/usr/lib/gcc-lib/i686-pc-cygwin/2.95.2
-L/usr/lib/gcc-lib/i686-pc-cygwin/2.95.2/../../../../i686-pc-cygwin/lib
usedll.o -lcdll -lgcc -lcygwin -luser32 -lkernel32 ladvapi32 -lshell32
-lgcc

CASE 2 (link direct to dll) 
mv libcdll.dll.a libcdll.dll.a.foo
ld -Bdynamic -o usedll-dll.exe /usr/lib/crt0.o -L./
-L/usr/lib/gcc-lib/i686-pc-cygwin/2.95.2
-L/usr/lib/gcc-lib/i686-pc-cygwin/2.95.2/../../../../i686-pc-cygwin/lib
usedll.o -lcdll -lgcc -lcygwin -luser32 -lkernel32 ladvapi32 -lshell32
-lgcc


Both usedll-imp.exe and usedll-dll.exe worked fine. Taking a look at the
executable symbols:

nm -a usedll-imp.exe | grep dll_global_int_var
008040b4 I __imp__dll_global_int_var

nm -a usedll-dll.exe | grep dll_global_int_var
008040e8 I __imp__dll_global_int_var
00801590 T _dll_global_int_var

Interesting: when using the import lib, you only get the __imp__ symbol,
but when linking directly to the dll (i.e. using a virtual import lib)
you get both symbols. In either case, however, the executable works
properly.

My earlier reported problems must have been due to mistakes in my hacked
up libpng, but I haven't located them. Sorry for the confusion.

--Chuck




(used the same link command to

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