[Bug python/11051] New: Undefined Python linker messages

[Bug python/11051] New: Undefined Python linker messages

[johndmcmaster at gmail dot com]

I get a number of linker messages along the line of "undefined reference to
`PyUnicodeUCS2_Decode'"  I saw someone had a similar issue for Samba
(http://lists.samba.org/archive/samba/2008-June/141536.html) indicating this may
be due to a bad Python install, but it got no replies.  I'm not that familar
with Python, but I noticed that while in /usr/lib/libpython2.4.so  there is no
PyUnicodeUCS2_Decode, there is a PyUnicodeUCS4_Decode.
Please let me know what other info you need.

GDB: 7.0
GCC: gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46)
OS: CentOS 5.3
Python: Python 2.4.6

Relevant output:
[mcmaster@gespenst gdb-7.0]$ make
...
gcc -g -O2      \
                -o gdb gdb.o libgdb.a \
                   ../readline/libreadline.a ../opcodes/libopcodes.a
../bfd/libbfd.a  ../libiberty/libiberty.a ../libdecnumber/libdecnumber.a   
-lncurses -lz -lm     -lpython2.4 -lexpat ../libiberty/libiberty.a 
gnulib/libgnu.a -ldl -rdynamic
libgdb.a(py-cmd.o): In function `cmdpy_completer':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-cmd.c:197:
undefined reference to `PyUnicodeUCS2_Decode'
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-cmd.c:200:
undefined reference to `PyUnicodeUCS2_Decode'
libgdb.a(py-cmd.o): In function `cmdpy_function':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-cmd.c:138:
undefined reference to `PyUnicodeUCS2_Decode'
libgdb.a(py-frame.o): In function `frapy_name':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-frame.c:132:
undefined reference to `PyUnicodeUCS2_Decode'
libgdb.a(py-frame.o): In function `gdbpy_frame_stop_reason_string':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-frame.c:407:
undefined reference to `PyUnicodeUCS2_Decode'
libgdb.a(py-type.o):/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-type.c:519:
more undefined references to `PyUnicodeUCS2_Decode' follow
libgdb.a(py-utils.o): In function `unicode_to_encoded_python_string':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-utils.c:117:
undefined reference to `PyUnicodeUCS2_AsEncodedString'
libgdb.a(py-utils.o): In function `unicode_to_encoded_string':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-utils.c:96:
undefined reference to `PyUnicodeUCS2_AsEncodedString'
libgdb.a(py-utils.o): In function `python_string_to_unicode':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-utils.c:73:
undefined reference to `PyUnicodeUCS2_FromEncodedObject'
libgdb.a(py-value.o): In function `valpy_string':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-value.c:254:
undefined reference to `PyUnicodeUCS2_Decode'
libgdb.a(py-value.o): In function `valpy_str':
/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb/./python/py-value.c:384:
undefined reference to `PyUnicodeUCS2_Decode'
collect2: ld returned 1 exit status
make[2]: *** [gdb] Error 1
make[2]: Leaving directory `/home/mcmaster/document/software/GNU/GDB/gdb-7.0/gdb'
make[1]: *** [all-gdb] Error 2
make[1]: Leaving directory `/home/mcmaster/document/software/GNU/GDB/gdb-7.0'
make: *** [all] Error 2

-- 
           Summary: Undefined Python linker messages
           Product: gdb
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: python
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: johndmcmaster at gmail dot com
                CC: gdb-prs at sourceware dot org


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[Bug python/11051] Undefined Python linker messages

[pmuldoon at redhat dot com]

------- Additional Comments From pmuldoon at redhat dot com  2010-02-23 17:48 -------
On first blush this look like the cause reported in the FAQ (which deals with
how Python is built for different environments):

http://www.python.org/doc/faq/extending/#when-importing-module-x-why-do-i-get-undefined-symbol-pyunicodeucs2

Can you run the testcase for determining the issue at the end of that article
and let us know?

Thanks


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[Bug python/11051] Undefined Python linker messages

[zilla at kayari dot org]

------- Additional Comments From zilla at kayari dot org  2010-03-22 12:51 -------
I'm getting the same error building GDB 7.1 on CentOS 5.3, with python 2.4
installed in /usr from rpm, and Python 2.6 in /usr/local

Python 2.6 comes first in my path so I expect that to be found by configure:
$ which python
/usr/local/bin/python

When I configure with --with-python=/usr/local or with no --with-python the
linker commands include -lpython2.6 (as expected) but I get undefined references
to the UCS2 symbols, and indeed the /usr/local/lib/libpython2.6.so library
doesn't have those symbols: 

$ nm /usr/local/lib/libpython2.6.so | fgrep UnicodeUCS2 | wc -l
0
$ nm /usr/local/lib/libpython2.6.so | fgrep UnicodeUCS4 | wc -l
84

The sys.maxunicode test gives

$  /usr/local/bin/python
Python 2.6.2 (r262:71600, Aug 18 2009, 15:29:02)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-44)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> if sys.maxunicode > 65535:
...    print 'UCS4 build'
... else:
...    print 'UCS2 build'
...
UCS2 build
>>>
$
$  /usr/bin/python
Python 2.4.3 (#1, Jul 27 2009, 17:56:30)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-44)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> if sys.maxunicode > 65535:
...    print 'UCS4 build'
... else:
...    print 'UCS2 build'
...
UCS4 build
>>>

I thought I would try to solve the problem by telling configure to use the UCS4
build of python2.4 in /usr, but when I configure with --with-python=/usr the
gdb-7.1/gdb/configure script still finds python2.6

configure:9442: checking whether to use python
configure:9444: result: /usr/
configure:9478: checking for python2.6
configure:9493: gcc -o conftest -g -O2   -I/usr//include   conftest.c -lncurses
-lz -lm    -L/usr//lib -lpython2.6 >&5
/usr/bin/ld: skipping incompatible /usr//lib/libncurses.so when searching for
-lncurses
/usr/bin/ld: skipping incompatible /usr//lib/libncurses.a when searching for
-lncurses
/usr/bin/ld: skipping incompatible /usr//lib/libz.so when searching for -lz
/usr/bin/ld: skipping incompatible /usr//lib/libz.a when searching for -lz
/usr/bin/ld: skipping incompatible /usr//lib/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr//lib/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr//lib/libc.so when searching for -lc
/usr/bin/ld: skipping incompatible /usr//lib/libc.a when searching for -lc
configure:9493: $? = 0
configure:9501: result: yes

There are a couple of problems here.  For a 64-bit OS LDFLAGS should use
-L/usr/lib64 not -L/usr/lib, secondly if libpython2.6 is found then it will be
used, even if it's not the one requested via --with-python  (this might be
unavoidable in a case like mine where python2.6 has been installed in
/usr/local, because GCC looks in /usr/local/lib for libraries.)

I can't change where python2.6 is installed, but I'd like to be able to use it,
which means I need to know why python2.6 reports a UCS2 build, but the library
only contains UCS4 symbols.
Presumably that is why gdb/python/py-cmd.c tries to link to the UCS2 symbols and
then fails to find them.

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[Bug python/11051] Undefined Python linker messages

[zilla at kayari dot org]

------- Additional Comments From zilla at kayari dot org  2010-03-22 12:55 -------
Hmm, curiously /usr/local/bin/python doesn't depend on libpython2.6.so which
might explain how it can report a UCS2 build when the lib only contains UCS4 symbols

$ ldd /usr/local/bin/python
        libpthread.so.0 => /lib64/libpthread.so.0 (0x0000003848e00000)
        libdl.so.2 => /lib64/libdl.so.2 (0x0000003848a00000)
        libutil.so.1 => /lib64/libutil.so.1 (0x000000384e200000)
        libm.so.6 => /lib64/libm.so.6 (0x000000384b200000)
        libc.so.6 => /lib64/libc.so.6 (0x0000003848200000)
        /lib64/ld-linux-x86-64.so.2 (0x0000003847a00000)


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[Bug python/11051] Undefined Python linker messages

[zilla at kayari dot org]

------- Additional Comments From zilla at kayari dot org  2010-03-22 13:11 -------
Looks like my headers don't match my .so:

$ fgrep Py_UNICODE_SIZE /usr/local/include/python2.6/pyconfig.h
#define Py_UNICODE_SIZE 2

So that explains why GDB tries to link to the UCS2 symbols.

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[Bug python/11051] Undefined Python linker messages

[zilla at kayari dot org]

------- Additional Comments From zilla at kayari dot org  2010-03-22 14:52 -------
Yes, we have a borked python2.6 installation.

To the OP: check which pyconfig.h GDB is including and see what it sets
Py_UNICODE_SIZE to. That needs to match what was used to build libpython2.4.so

To the GDB maintainers: I think the configure checks for python could be
improved, but at least in my case this bug seems to be caused by user error.

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[Bug python/11051] Undefined Python linker messages

[johndmcmaster at gmail dot com]

------- Additional Comments From johndmcmaster at gmail dot com  2010-03-22 15:04 -------
Yes, that's the idea I was trying to get across when I posted this: if this is a
user error, is it possible for configure to notify us rather than during build?
 And now from the FAQ entry that was pointed to, it seems that this is a pretty
common issue and would be worth checking for if relatively easy to check for.  I
did verify that there was a mismatch in python files and was able to eliminate
the second Python installation which seems to have fixed the problem.  However,
part of the the idea of configure is to make sure the build environment is sane,
and this seemed big enough that would be worthwhile to be checked in configure.

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[Bug python/11051] Undefined Python linker messages

[pmuldoon at redhat dot com]

------- Additional Comments From pmuldoon at redhat dot com  2010-06-30 09:17 -------
"To the OP: check which pyconfig.h GDB is including and see what it sets
Py_UNICODE_SIZE to. That needs to match what was used to build libpython2.4.so

To the GDB maintainers: I think the configure checks for python could be
improved, but at least in my case this bug seems to be caused by user error."

I'm not sure how we have GDB's configure  check the PU_UNICODE_SIZE against what
was used to build libpython2.so.  I'm not expert here, by far. 


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[Bug python/11051] Undefined Python linker messages

[tromey at redhat dot com]

------- Additional Comments From tromey at redhat dot com  2010-06-30 17:35 -------
(In reply to comment #7)

> I'm not sure how we have GDB's configure  check the PU_UNICODE_SIZE against what
> was used to build libpython2.so.  I'm not expert here, by far. 

We probably don't want to do that.  It seems reasonable to me to assume
that Python is installed correctly.

The configury here has all been redone in CVS.  I think it is somewhat more
robust.  So, I'm closing this; if you think that this is in error, please
reopen.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED


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