Re: [9fans] 9P in C++
On Thu, Dec 18, 2008 at 7:14 AM, Rodolfo kix Garcia wrote:
> Pietro Gagliardi escribió:
>> extern "C"{
>> #include <9p.h> // or whatever you do
>> }
>>
>> you can link 9p into a C++ program easily.
>
> If I use the extern "C" it compiles :'-)
>
> Using "extern function" is not valid for linking C and C++
extern works fine between C and C++, but maybe it doesn't do what you
think it does. extern assures the compiler that there is a symbol with
a certain type defined in some other object than the one currently
being compiled.
What you're running into is a name mangling issue. C++ supports
overloaded functions, ie. functions with the same name but different
prototypes. This doesn't fly with the linker, because as far as it is
concerned each symbol has a unique type[1]. So, C++ mangles[2] the
function name by appending a string representation of the prototype.
int main(int, char**) maps to a symbol like main_i_i_ppc. The mangled
notation is compiler specific of course.
This presents a problem for interoperation with C code. Any existing
library compiled by a C compiler has regular non-mangled names. But, a
C++ compiler will grab the prototypes from the library's header file,
and then tell the linker to look for mangled versions of the symbols.
Obviously it is not going to find them.
So, as a workaround, C++ overloads the extern keyword to allow the form:
extern "C" {
...
}
Which tells the compiler "the functions defined in this block were
compiled with a C compiler, don't mangle the symbols".
[1] Does the linker actually know about types or just sizes?
[2] "mangles" is official terminology, so at least they're honest about it. ;)
-sqweek
Re: [9fans] 9P in C++
Pietro Gagliardi escribió:
Given
extern "C"{
#include <9p.h> // or whatever you do
}
you can link 9p into a C++ program easily.
Yes!
If I use the extern "C" it compiles :'-)
Using "extern function" is not valid for linking C and C++
Sorry Pietro, sqweek. Thanks a lot.
Re: [9fans] 9P in C++
Thanks Pietro, sqweek,
I can't compile it :-/
Some info:
k...@sys:~/2008110109$ cat Makefile
all:
g++ -Wall -fPIC -c a.C
g++ -Wall -fPIC -c b.C
g++ -Wall -fPIC -c c.C
9c -Wall -o tryfs.o tryfs.c
9l -Wall -shared -lthread -o libtry.so a.o b.o c.o tryfs.o
/usr/local/plan9/lib/libthread.a
g++ -Wall -g -o simple-01 simple-01.C -L. -l try -lstdc++
k...@sys:~/2008110109$ make
...
9l -Wall -shared -lthread -o libtry.so a.o b.o c.o tryfs.o
/usr/local/plan9/lib/libthread.a
g++ -Wall -g -o simple-01 simple-01.C -L. -l try -lstdc++
./libtry.so: undefined reference to `threadmain(int, char**)'
collect2: ld returned 1 exit status
make: *** [all] Error 1
k...@sys:~/2008110109$ ldd libtry.so
linux-gate.so.1 => (0xb7eed000)
libresolv.so.2 => /lib/i686/cmov/libresolv.so.2 (0xb7ece000)
libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb7ea8000)
libutil.so.1 => /lib/i686/cmov/libutil.so.1 (0xb7ea3000)
libpthread.so.0 => /lib/i686/cmov/libpthread.so.0 (0xb7e8a000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7d2f000)
/lib/ld-linux.so.2 (0xb7eee000)
In the tryfs.c file:
void
threadmain(int argc, char *argv[])
{
}
Thanks.
Pietro Gagliardi wrote:
-l/usr/local/plan9/lib/libthread.so (or whatever it is) help?
You can't use -l with a full path, but you can simply specify the
full path of the library:
gcc -o demo1 demo1.C /usr/local/plan9/lib/libthread.a
Note that the order of the objects on the command-line is as usual
important.
-sqweek
Ah yes, something I forgot while drifting through the hordes of gcc
madness that is... not using gcc. Thanks for refreshing my memory. Now
to see if this is working for kix.
Re: [9fans] 9P in C++
On Dec 15, 2008, at 9:16 PM, sqweek wrote: On Tue, Dec 16, 2008 at 8:34 AM, Pietro Gagliardi wrote: On Dec 15, 2008, at 6:25 PM, Rodolfo kix Garcia wrote: gcc -L /usr/local/plan9/lib -L. -ltry -lthread demo1.C -o demo1 ## OK! I think linking lthread will give you POSIX threads and that -L appends to the list, rather than going before, so /usr/lib will be searched before plan9ports. Try explicitly setting the path of the -l argument. Does -l/usr/local/plan9/lib/libthread.so (or whatever it is) help? You can't use -l with a full path, but you can simply specify the full path of the library: gcc -o demo1 demo1.C /usr/local/plan9/lib/libthread.a Note that the order of the objects on the command-line is as usual important. -sqweek Ah yes, something I forgot while drifting through the hordes of gcc madness that is... not using gcc. Thanks for refreshing my memory. Now to see if this is working for kix. PGP.sig Description: This is a digitally signed message part
Re: [9fans] 9P in C++
On Tue, Dec 16, 2008 at 8:34 AM, Pietro Gagliardi wrote: > On Dec 15, 2008, at 6:25 PM, Rodolfo kix Garcia wrote: >> gcc -L /usr/local/plan9/lib -L. -ltry -lthread demo1.C -o demo1 ## OK! > > I think linking lthread will give you POSIX threads and that -L appends to > the list, rather than going before, so /usr/lib will be searched before > plan9ports. Try explicitly setting the path of the -l argument. Does > -l/usr/local/plan9/lib/libthread.so (or whatever it is) help? You can't use -l with a full path, but you can simply specify the full path of the library: gcc -o demo1 demo1.C /usr/local/plan9/lib/libthread.a Note that the order of the objects on the command-line is as usual important. -sqweek
Re: [9fans] 9P in C++
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On Dec 15, 2008, at 6:25 PM, Rodolfo kix Garcia wrote: gcc -L /usr/local/plan9/lib -L. -ltry -lthread demo1.C -o demo1 ## OK! I think linking lthread will give you POSIX threads and that -L appends to the list, rather than going before, so /usr/lib will be searched before plan9ports. Try explicitly setting the path of the -l argument. Does -l/usr/local/plan9/lib/libthread.so (or whatever it is) help? -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.8 (Darwin) iEYEARECAAYFAklG6YAACgkQuv7AVNQDs+xs6QCfZy4CD480VMiv8DN2VyX2ydDs WzYAn0sEgTbpQM9Z/8ieACzLVBx15okU =Jzfc -END PGP SIGNATURE-
Re: [9fans] 9P in C++
Pietro Gagliardi escribió:
Given
extern "C"{
#include <9p.h> // or whatever you do
}
you can link 9p into a C++ program easily.
Thanks Pietro :-)
I use:
#include stdio.h
#include blablabla.h
extern void threadmain(int c, char *a[])
Now the file compiles. But I have other problem.
gcc -L. -ltry -o demo1 demo1.C
./libtry.so: Undefined reference to threadmain(...)
Then, I try:
gcc -L /usr/local/plan9/lib -L. -ltry -lthread demo1.C -o demo1 ## OK!
./demo1
Segmentation Fault
using ldd I can see libthread is /usr/lib/libthread, not in the
plan9port three.
Any help?
Thanks a lot.
Re: [9fans] 9P in C++
On Dec 15, 2008, at 10:45 AM, Rodolfo kix García wrote:
Hi!
I am working in an c++ application on linux and I would like to use a
filesystem to access to the application data.
Somebody knows any 9P implementation of 9P in C++?
Thanks,
Saludos, kix.
--
Rodolfo García AKA kix
http://www.kix.es/
EA4ERH (@IN80ER)
Given
extern "C"{
#include <9p.h> // or whatever you do
}
you can link 9p into a C++ program easily.
PGP.sig
Description: This is a digitally signed message part
Re: [9fans] 9P in C++
On Mon, Dec 15, 2008 at 1:45 PM, Rodolfo kix García wrote: > Hi! > > I am working in an c++ application on linux and I would like to use a > filesystem to access to the application data. > > Somebody knows any 9P implementation of 9P in C++? > any issues with using the ones in C? iru
Re: [9fans] 9P in C++
On Tue, Dec 16, 2008 at 12:45 AM, Rodolfo kix García wrote: > Hi! > > I am working in an c++ application on linux and I would like to use a > filesystem to access to the application data. > > Somebody knows any 9P implementation of 9P in C++? Don't see one at http://9p.cat-v.org/implementations Of course any C implementation like libixp will work fine. -sqweek
[9fans] 9P in C++
Hi! I am working in an c++ application on linux and I would like to use a filesystem to access to the application data. Somebody knows any 9P implementation of 9P in C++? Thanks, Saludos, kix. -- Rodolfo García AKA kix http://www.kix.es/ EA4ERH (@IN80ER)
