Embedding Python

[Markus Franz]

Hi!

I wanted to run some Python code from inside a C program, so I did it
like it was explained in the Python manual:

#include <Python.h>
int main(int argc, char *argv[]) {
Py_Initialize() ;
PyRun_SimpleStr ing("print 'Hallo World!'\n");
Py_Finalize();
return 0;
}

Then I tried to compile this by using the command: gcc halloworld.cpp
But everytime I get the following errors:

/home/mmf/tmp/ccVD2V4h.o(.tex t+0x1d): In function `main':
: undefined reference to `Py_Initialize'
/home/mmf/tmp/ccVD2V4h.o(.tex t+0x2a): In function `main':
: undefined reference to `PyRun_SimpleSt ring'
/home/mmf/tmp/ccVD2V4h.o(.tex t+0x32): In function `main':
: undefined reference to `Py_Finalize'
/home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
`__gxx_personal ity_v0'
collect2: ld returned 1 exit status

What am I doing wrong?

Markus

[Diez B. Roggisch]

Re: Embedding Python

> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x1d): In function `main':[color=blue]
> : undefined reference to `Py_Initialize'
> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x2a): In function `main':
> : undefined reference to `PyRun_SimpleSt ring'
> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x32): In function `main':
> : undefined reference to `Py_Finalize'
> /home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
> `__gxx_personal ity_v0'
> collect2: ld returned 1 exit status
>
> What am I doing wrong?[/color]

Not linking against libpython.so?
--
Regards,

Diez B. Roggisch

[Markus Franz]

Re: Embedding Python

Diez B. Roggisch wrote:
[color=blue][color=green]
>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x1d): In function `main':
>>: undefined reference to `Py_Initialize'
>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x2a): In function `main':
>>: undefined reference to `PyRun_SimpleSt ring'
>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x32): In function `main':
>>: undefined reference to `Py_Finalize'
>>/home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
>>`__gxx_person ality_v0'
>>collect2: ld returned 1 exit status
>>
>>What am I doing wrong?[/color]
>
> Not linking against libpython.so?[/color]

I don't understand what you mean...

Markus

[Diez B. Roggisch]

Re: Embedding Python

Markus Franz wrote:
[color=blue]
> Diez B. Roggisch wrote:
>[color=green][color=darkred]
>>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x1d): In function `main':
>>>: undefined reference to `Py_Initialize'
>>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x2a): In function `main':
>>>: undefined reference to `PyRun_SimpleSt ring'
>>>/home/mmf/tmp/ccVD2V4h.o(.tex t+0x32): In function `main':
>>>: undefined reference to `Py_Finalize'
>>>/home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
>>>`__gxx_perso nality_v0'
>>>collect2: ld returned 1 exit status
>>>
>>>What am I doing wrong?[/color]
>>
>> Not linking against libpython.so?[/color]
>
> I don't understand what you mean...[/color]

Well, you need to link against the python library to make known where the
respective symbols are from. That is also necessary for all other libs out
there - e.g. the linker switch -lm links against libm.so. For someone who
_codes_ in C/C++ that should be obvious - or so I thought. What
build-environment do you use?

The line
[color=blue][color=green][color=darkred]
>>>/home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
>>>`__gxx_perso nality_v0'[/color][/color][/color]

suggest that you also miss linking against libstdc++ - an error that
sometimes happened to me too - no idea why, it _should_ be included
implicitely when linking C++ objects. No big deal though, just also add it
to the linking process.
--
Regards,

Diez B. Roggisch

[Mark Tolonen]

Re: Embedding Python


"Markus Franz" <mf1987@arcor.d e> wrote in message
news:576fb15a.0 503260342.15ea4 630@posting.goo gle.com...[color=blue]
> Hi!
>
> I wanted to run some Python code from inside a C program, so I did it
> like it was explained in the Python manual:
>
> #include <Python.h>
> int main(int argc, char *argv[]) {
> Py_Initialize() ;
> PyRun_SimpleStr ing("print 'Hallo World!'\n");
> Py_Finalize();
> return 0;
> }
>
> Then I tried to compile this by using the command: gcc halloworld.cpp
> But everytime I get the following errors:
>
> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x1d): In function `main':
> : undefined reference to `Py_Initialize'
> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x2a): In function `main':
> : undefined reference to `PyRun_SimpleSt ring'
> /home/mmf/tmp/ccVD2V4h.o(.tex t+0x32): In function `main':
> : undefined reference to `Py_Finalize'
> /home/mmf/tmp/ccVD2V4h.o(.eh_ frame+0x11): undefined reference to
> `__gxx_personal ity_v0'
> collect2: ld returned 1 exit status
>
> What am I doing wrong?
>
> Markus[/color]

This works for me on Redhat 9:

g++ x.cpp -o x -I/usr/include/python2.2 -pthread -lm
-ldl -lutil /usr/lib/python2.2/config/libpython2.2.a

I discovered what libraries to link to by asking distutils:

import distutils.sysco nfig
distutils.sysco nfig.get_config _var('LIBS')
distutils.sysco nfig.get_config _var('SYSLIBS')

g++ links to the right libraries for .cpp files.

-Mark

[Diez B. Roggisch]

Re: Embedding Python

> This works for me on Redhat 9:[color=blue]
>
> g++ x.cpp -o x -I/usr/include/python2.2 -pthread -lm
> -ldl -lutil /usr/lib/python2.2/config/libpython2.2.a
>[/color]

Why did you chose the static variant? This should be equivalent:

g++ x.cpp -o x -I/usr/include/python2.2 -pthread -lm
-ldl -lutil -lpython2.2

--
Regards,

Diez B. Roggisch

[Mark Tolonen]

Re: Embedding Python


"Diez B. Roggisch" <deetsNOSPAM@we b.de> wrote in message
news:d24ao4$8c1 $00$1@news.t-online.com...[color=blue][color=green]
>> This works for me on Redhat 9:
>>
>> g++ x.cpp -o x -I/usr/include/python2.2 -pthread -lm
>> -ldl -lutil /usr/lib/python2.2/config/libpython2.2.a
>>[/color]
>
> Why did you chose the static variant? This should be equivalent:
>
> g++ x.cpp -o x -I/usr/include/python2.2 -pthread -lm
> -ldl -lutil -lpython2.2
>
> --
> Regards,
>
> Diez B. Roggisch[/color]

On my system, for whatever reason, the .so library isn't present. I have
the python-devel package installed.

-Mark

[Heiko Wundram]

Re: Embedding Python

Am Samstag, 26. März 2005 20:43 schrieb Mark Tolonen:[color=blue]
> On my system, for whatever reason, the .so library isn't present. I have
> the python-devel package installed.[/color]

I actually can't believe this; do

ldconfig -p|grep "python"

as root and look for any output. And remember that the shared library isn't
installed by the devel package, but by the standard python package, as the
binary /usr/bin/python is only a "stub", which chains to the python
interpreter in the shared lib (at least for any distribution I know of, it
would be braindead to link the command-line interpreter statically anyway).

Sample output:

heiko heiko # ldconfig -p|grep python
libpython2.4.so .1.0 (libc6) => /usr/local/lib/libpython2.4.so .1.0
libpython2.4.so (libc6) => /usr/local/lib/libpython2.4.so
libpython2.3.so .1.0 (libc6) => /usr/lib/libpython2.3.so .1.0
libpython2.3.so (libc6) => /usr/lib/libpython2.3.so
heiko heiko #

--
--- Heiko.

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[Reinhold Birkenfeld]

Re: Embedding Python

Heiko Wundram wrote:[color=blue]
> Am Samstag, 26. März 2005 20:43 schrieb Mark Tolonen:[color=green]
>> On my system, for whatever reason, the .so library isn't present. I have
>> the python-devel package installed.[/color]
>
> I actually can't believe this; do
>
> ldconfig -p|grep "python"[/color]

Or, use

ldd =python

to exactly display what library your current executable is using.

(users of a shell other than Zsh must replace '=python' by '`which python`')


Reinhold

[Mark Tolonen]

Re: Embedding Python


"Reinhold Birkenfeld" <reinhold-birkenfeld-nospam@wolke7.n et> wrote in
message news:3altmaF6ca j9aU1@individua l.net...[color=blue]
> Heiko Wundram wrote:[color=green]
>> Am Samstag, 26. März 2005 20:43 schrieb Mark Tolonen:[color=darkred]
>>> On my system, for whatever reason, the .so library isn't present. I
>>> have
>>> the python-devel package installed.[/color]
>>
>> I actually can't believe this; do
>>
>> ldconfig -p|grep "python"[/color]
>
> Or, use
>
> ldd =python
>
> to exactly display what library your current executable is using.
>
> (users of a shell other than Zsh must replace '=python' by '`which
> python`')
>
>
> Reinhold[/color]

$ ldd /usr/bin/python
libdl.so.2 => /lib/libdl.so.2 (0x40023000)
libpthread.so.0 => /lib/tls/libpthread.so.0 (0x40028000)
libutil.so.1 => /lib/libutil.so.1 (0x40036000)
libm.so.6 => /lib/tls/libm.so.6 (0x40039000)
libc.so.6 => /lib/tls/libc.so.6 (0x42000000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

I also (before I originally posted) did a "find / -name libpython*" with no
success. Looks like Redhat 9 ships with a statically linked version of
python.

-Mark

[Heiko Wundram]

Re: Embedding Python

Am Samstag, 26. März 2005 21:36 schrieb Mark Tolonen:[color=blue]
> I also (before I originally posted) did a "find / -name libpython*" with no
> success. Looks like Redhat 9 ships with a statically linked version of
> python.[/color]

Hmm... Sorry to have thought otherwise... RedHat is braindead. :-)

--
--- Heiko.

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