Re: Linking shared libraries problem
Larry Hall (Cygwin) wrote: On 8/29/2010 7:08 PM, Tomás Staig wrote: Hi, I have been trying to port some software from Linux (Scientific Linux/RedHat) to windows using Cygwin. I have been able to port most of it with little changes but I encountered a problem when linking shared libraries. It seems that the chain of dependencies is not included when linking. Furthermore, ldd does not show the dependency libraries as in Linux. I have tried both using the import libraries (%.dll.a) and linking the dll files (%.dll) directly. I have arranged a small example program that reproduces this effect. Used Ubuntu 8.04 to and CYGWIN_NT-5.1 version 1.7.6(0.230/5/3) 2010-08-16 16:06 on top of a 32-bits Windows XP Machine to test the above examples. snip As you can see, there is no reference to liby.dll. I could add the library (-ly) directly to the compiling line of main and it works, but the truth is that it would not be a good approach, since in the software I'm trying to port, there are several dependent modules, so the last ones would have an incredibly large list of dependencies. So, am I doing something wrong? Is there any way to add the dependency to be shown with ldd or any workaround(maybe a linker flag or something) to make the above example work? The Windows loader requires full resolution at link time. You need to list at least the import libraries for all dependencies if you want the link to succeed. Sorry, that's just the way Windows works. Thanks for your reply. I have found a workaround, however. Probably not the best thing to do in general, but for my case it is pretty useful: Makefile in Cygwin: all: g++ -c x.cpp g++ -c y.cpp g++ -shared -Wl,--output-def,liby.def -Wl,-out-implib=liby.dll.a -Wl,-export-all-symbols -Wl,-enable-auto-import -Wl,-whole-archive y.o -Wl,-no-whole-archive -o liby.dll g++ -shared -Wl,-out-implib=libx.dll.a -Wl,-export-all-symbols -Wl,-enable-auto-import -Wl,-whole-archive x.o liby.def -Wl,-no-whole-archive -L./ -ly -o libx.dll g++ -o main main.cpp -L./ -lx If anyone is going to use this, be aware that it might get you multiple definition problems. I still haven't checked how this behaves in the project I'm porting, but in this tiny example it works flawlessly. -- 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
Linking shared libraries problem
Hi,
I have been trying to port some software from Linux (Scientific
Linux/RedHat) to windows using Cygwin. I have been able to port most of
it with little changes but I encountered a problem when linking shared
libraries. It seems that the chain of dependencies is not included when
linking. Furthermore, ldd does not show the dependency libraries as in
Linux. I have tried both using the import libraries (%.dll.a) and
linking the dll files (%.dll) directly.
I have arranged a small example program that reproduces this effect.
Used Ubuntu 8.04 to and CYGWIN_NT-5.1 version 1.7.6(0.230/5/3)
2010-08-16 16:06 on top of a 32-bits Windows XP Machine to test the
above examples.
x.h:
int add(int a, int b);
x.cpp:
#include x.h
int add(int a, int b) {return a + b;}
y.h:
int sub(int a, int b);
y.cpp:
#include y.h
int sub(int a, int b){return a - b;}
main.cpp:
#include stdio.h
#include x.h
#include y.h
int main()
{
printf(%d\n,add(1,1));
printf(%d\n,sub(2,1));
return 0;
}
Makfile in Linux:
#Compiling
all:
g++ -c x.cpp
g++ -c y.cpp
g++ -shared -Wl,-whole-archive y.o -Wl,-no-whole-archive -o liby.so
g++ -shared -Wl,-whole-archive x.o -Wl,-no-whole-archive -L./ -ly -o
libx.so
g++ -o main main.cpp -L./ -lx
Makefile in Cygwin:
all:
g++ -c x.cpp
g++ -c y.cpp
g++ -shared y.o -Wl,-out-implib=liby.dll.a -Wl,-export-all-symbols
-Wl,-enable-auto-import -Wl,-whole-archive -Wl,-no-whole-archive -o liby.dll
g++ -shared x.o -Wl,-out-implib=libx.dll.a -Wl,-export-all-symbols
-Wl,-enable-auto-import -Wl,-whole-archive -Wl,-no-whole-archive -L./
-ly -o libx.dll
g++ -o main main.cpp -L./ -lx
Linux does not produce any output and the program 'main' works.
Cygwin Output:
/tmp/cc0LNesq.o:main.cpp:(.text+0x4a): undefined reference to `sub(int,
int)'
collect2: ld returned 1 exit status
make: *** [all] Error 1
If I use ldd in Linux for libx.so:
$ ldd libx.so
linux-gate.so.1 = (0xb772f000)
liby.so (0xb7729000)
libstdc++.so.6 = /usr/lib/libstdc++.so.6 (0xb7635000)
libm.so.6 = /lib/tls/i686/cmov/libm.so.6 (0xb75f9000)
libgcc_s.so.1 = /lib/libgcc_s.so.1 (0xb75ee000)
libc.so.6 = /lib/tls/i686/cmov/libc.so.6 (0xb749f000)
/lib/ld-linux.so.2 (0xb773)
and in Cygwin for libx.dll:
$ ldd libx.dll
ntdll.dll = /cygdrive/c/WINDOWS/system32/ntdll.dll (0x7c91)
kernel32.dll = /cygdrive/c/WINDOWS/system32/kernel32.dll (0x7c80)
As you can see, there is no reference to liby.dll. I could add the
library (-ly) directly to the compiling line of main and it works, but
the truth is that it would not be a good approach, since in the software
I'm trying to port, there are several dependent modules, so the last
ones would have an incredibly large list of dependencies.
So, am I doing something wrong? Is there any way to add the dependency
to be shown with ldd or any workaround(maybe a linker flag or something)
to make the above example work?
Thanks in advance.
Best Regards,
Tomas.
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Re: Linking shared libraries problem
On 8/29/2010 7:08 PM, Tomás Staig wrote: Hi, I have been trying to port some software from Linux (Scientific Linux/RedHat) to windows using Cygwin. I have been able to port most of it with little changes but I encountered a problem when linking shared libraries. It seems that the chain of dependencies is not included when linking. Furthermore, ldd does not show the dependency libraries as in Linux. I have tried both using the import libraries (%.dll.a) and linking the dll files (%.dll) directly. I have arranged a small example program that reproduces this effect. Used Ubuntu 8.04 to and CYGWIN_NT-5.1 version 1.7.6(0.230/5/3) 2010-08-16 16:06 on top of a 32-bits Windows XP Machine to test the above examples. snip As you can see, there is no reference to liby.dll. I could add the library (-ly) directly to the compiling line of main and it works, but the truth is that it would not be a good approach, since in the software I'm trying to port, there are several dependent modules, so the last ones would have an incredibly large list of dependencies. So, am I doing something wrong? Is there any way to add the dependency to be shown with ldd or any workaround(maybe a linker flag or something) to make the above example work? The Windows loader requires full resolution at link time. You need to list at least the import libraries for all dependencies if you want the link to succeed. Sorry, that's just the way Windows works. -- Larry Hall http://www.rfk.com RFK Partners, Inc. (508) 893-9779 - RFK Office 216 Dalton Rd. (508) 893-9889 - FAX Holliston, MA 01746 _ A: Yes. Q: Are you sure? A: Because it reverses the logical flow of conversation. Q: Why is top posting annoying in email? -- 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
