undefined symbol: PyExc_SystemError

[jenner]

OS: Debian Buster
mod_python: master HEAD (7af8011)

/usr/src/mod_python# ./configure --with-python=/usr/bin/python3
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking for ar... ar
checking for a BSD-compatible install... /usr/bin/install -c
checking whether make sets $(MAKE)... yes
checking for main in -lm... yes
checking for an ANSI C-conforming const... yes
checking your blood pressure... a bit high, but we can proceed
configure: checking whether apxs is available...
checking for apxs2... /usr/bin/apxs2
checking Apache version... 2.4.38
checking for Apache libexec directory... /usr/lib/apache2/modules
checking for Apache include directory... -I/usr/include/apache2
checking for --with-python... /usr/bin/python3
checking Python version... 3.7
checking for --with-mutex-dir... no
Using MUTEX_DIR /tmp
checking for --with-max-locks... no
Using 8 MAX_LOCKS.
checking for --with-flex... no
checking for flex... /usr/bin/flex
found /usr/bin/flex, we'll use this. Use --with-flex to specify another.
checking flex version... configure: WARNING: Flex version 2.6.4 found.
    Version 2.5.31 or greater is required.  You can generally ignore this
    warning unless you need to regenerate psp_parser.c from psp_parse.l.
    If you do need regenerate psp_parser.c, use --with-flex to specify the
    location of the correct flex version. See the README for more information.
configure: creating ./config.status
config.status: creating Makefile
config.status: creating src/Makefile
config.status: creating Doc/Makefile
config.status: creating src/include/mod_python.h
config.status: creating test/Makefile
config.status: creating dist/setup.py
config.status: creating dist/Makefile
config.status: creating scripts/Makefile
config.status: creating scripts/mod_python

Running make test yields following errors: apache2: Syntax error on line 57 of /usr/src/mod_python/test/conf/test.conf: Cannot load /usr/src/mod_python/src/mod_python.so into server: /usr/src/mod_python/src/mod_python.so: undefined symbol: PyExc_SystemError

Seems like libpython is not linked properly:

:/usr/src/mod_python# ldd src/mod_python.so 
	linux-vdso.so.1 (0x00007fffd907c000)
	libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f4494320000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f44942ff000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f44942f0000)
	libutil.so.1 => /lib/x86_64-linux-gnu/libutil.so.1 (0x00007f44942e0000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4494110000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f449439d000)

Any hints on how to solve this?

Thanks in advance
Igor

[jenner]

Found the problem: in ecbdcf1 print(distutils.sysconfig.get_config_var("LDLIBRARY")) yields libpython3.7m.so, which is not a valid linker argument. Replacing it with print(distutils.sysconfig.get_config_var("BLDLIBRARY")) works though:

~# python3.7 -c 'import distutils.sysconfig; print(distutils.sysconfig.get_config_var("BLDLIBRARY"))'
-lpython3.7m

I guess the config var depends on the platform.

[ewah]

BLDLIBRARY isn't consistent depending on the how the original python got built.

> python  -m sysconfig | grep BLDLIB
	BLDLIBRARY = "-L. -lpython2.7"

> python  -m sysconfig | grep BLDLIB
	BLDLIBRARY = ""

> python -m sysconfig | grep BLDLIB
	BLDLIBRARY = "libpython3.8.a"

---

locally i've reverted the config code back to pre-ecbdcf17884551b823fcef12cd5bd91103bde1fc (nov 7, 2019)

+    if test "$PyMAJVERSION" -eq "3"; then
+        LDLIBS1="-lpython${PyMAJVERSION}"
+    else
+        LDLIBS1="-lpython${PyVERSION}"
+    fi
-    LDLIBS1=`${PYTHON_BIN} -c 'import distutils.sysconfig;\
-        print(distutils.sysconfig.get_config_var("LDLIBRARY"))'`

[thkatsou]

trying to compile mod-python on ubuntu 20.10 against python 2.7 .
Compilation and installation goes ok but apache2 does not start with same error.

apachectl configtest
apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/python.load: Cannot load /usr/lib/apache2/modules/mod_python.so into server: /usr/lib/apache2/modules/mod_python.so: undefined symbol: PyExc_SystemError
Action 'configtest' failed.
The Apache error log may have more information.

tried all of the patches on makefile.in still no luck.

update: this modification on configure script worked ana apache2 started.
0e436f1
now I am facing
ImportError: Import by filename is not supported.

[diegobill]

any update from this error? I am still seeing on Docker in Ubuntu 16.04:

FROM python:2.7.18-slim

# Install packages
RUN apt-get -yqq update && \
    apt-get -yqq install mercurial git vim apache2 apache2-dev libapache2-mod-python openssl libmariadb-dev fonts-freefont-ttf libssl-dev cron logrotate lynx htop zabbix-agent && \
    apt-get clean

WORKDIR /usr/local/src
RUN git clone git+https://github.com/grisha/mod_python.git@e7ec956eaeba9f75e33f5d0036a6699ac3f0d816
WORKDIR /usr/local/src/mod_python
COPY patches/patch-Py_Initialize.txt /tmp
RUN LIBS="-lpython2.7" ./configure && \
    # configure gets the libpython2.7.so link argument wrong, so fix it
    sed -i.bak 's/libpython2.7.so/-lpython2.7/g' /usr/local/src/mod_python/src/Makefile && \
    patch -p1 < /tmp/patch-Py_Initialize.txt && \
    LIBS="-lpython2.7" make && \
    make install