Undefined symbol warning_at when loading gcc-python-plugin

[David Narvaez <david dot narvaez at computer dot org>]

Hi all,

I'm new to GCC etc, so I am going to add a lot of info which may not be needed:

I'm trying to package gcc-python-plugin[0] for Gentoo on amd64, but
after compiling the python.so library, I cannot load it into gcc as a
plugin because of the following error:

cc1: error: cannot load plugin
/var/tmp/portage/dev-util/gcc-python-plugin-0.10/work/gcc-python-plugin-0.10-3.2/python.so
/var/tmp/portage/dev-util/gcc-python-plugin-0.10/work/gcc-python-plugin-0.10-3.2/python.so:
undefined symbol: warning_at

This is happening only in GCC 4.7.1 x86_64-pc-linux-gnu. I am able to
compile and load the plugin using GCC 4.6.3 x86_64-pc-linux-gnu and
GCC 4.7.1 x86. I have tried a couple of things which have led me to
think this is an issue with the symbol table in the python.so library.
Here are some (I think) relevant nm outputs:

# nm -C python.so | grep -C 5 warning_at
                 U varpool_nodes
0000000000031890 T VEC_edge_as_PyList
0000000000035330 T VEC_tree_as_PyList
                 U walk_gimple_op
                 U warn_format
                 U warning_at
0000000000031e00 T wrtp_mark_for_PyGccBasicBlock
0000000000031680 T wrtp_mark_for_PyGccCallgraphEdge
0000000000031690 T wrtp_mark_for_PyGccCallgraphNode
0000000000031f90 T wrtp_mark_for_PyGccCfg
0000000000031880 T wrtp_mark_for_PyGccEdge

** Notice the warning_at signature; there's actually no function
symbol with signature in the whole table

# nm -C /usr/lib/debug/usr/libexec/gcc/x86_64-pc-linux-gnu/4.7.1/cc1.debug
| grep -C 5 warning_at
000000000090f350 T union_defs(df_ref_d*, web_entry*, unsigned int*,
web_entry*, bool (*)(web_entry*, web_entry*))
00000000007de1a0 T update_ssa(unsigned int)
00000000008e0b60 T vec_member(tree_node const*, VEC_tree_gc*)
00000000008957b0 T verify_ssa(bool)
0000000000775e90 T vinsn_copy(vinsn_def*, bool)
0000000000c18b50 T warning_at(unsigned int, int, char const*, ...)
00000000007effa0 T add_phi_arg(gimple_statement_d*, tree_node*,
edge_def*, unsigned int)
000000000057b800 T alloc_block()
000000000080d650 T ao_ref_base(ao_ref_s*)
000000000080d600 T ao_ref_init(ao_ref_s*, tree_node*)
000000000062c910 T app_disable()

** Again, the warning_at symbol, but with signature

# nm -C /usr/lib/debug/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/cc1.debug
| grep -C 5 warning_at
00000000008b4160 T warn_function_noreturn
00000000006999d0 T warn_if_plugins
00000000004a6800 t warn_if_shadowing
000000000071c060 T warn_if_unused_value
000000000057b9d0 T warning
000000000057b910 T warning_at
00000000004defe0 t warning_candidate_p
00000000006df9f0 T warning_for_asm
00000000004b78a0 t warning_init
00000000010e13b3 b warning_issued.44446
00000000004e3270 T warnings_for_convert_and_chec

** warning_at with no signature in GCC 4.6.3

Compilation flags for the plugin are:

CPPFLAGS+= -I$(GCCPLUGINS_DIR)/include
-I$(GCCPLUGINS_DIR)/include/c-family -I. $(PYTHON_INCLUDES)
CFLAGS?=-O2 -Werror -g
CFLAGS+= -fPIC -fno-strict-aliasing -Wall

I'm not using any special LDFLAGS. A compilation line of the plugin
looks like this:

cc -O2 -Werror -g -fPIC -fno-strict-aliasing -Wall
-I/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/plugin/include
-I/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/plugin/include/c-family -I.
-I/usr/include/python2.7 -I/usr/include/python2.7   -c -o
autogenerated-variable.o autogenerated-variable.c

Linking looks like this

cc -I/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/plugin/include
-I/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/plugin/include/c-family -I.
-I/usr/include/python2.7 -I/usr/include/python2.7 -O2 -Werror -g -fPIC
-fno-strict-aliasing -Wall  -shared gcc-python.o
gcc-python-attribute.o gcc-python-callbacks.o gcc-python-callgraph.o
gcc-python-cfg.o gcc-python-closure.o gcc-python-diagnostics.o
gcc-python-function.o gcc-python-gimple.o gcc-python-location.o
gcc-python-option.o gcc-python-parameter.o gcc-python-pass.o
gcc-python-pretty-printer.o gcc-python-rtl.o gcc-python-tree.o
gcc-python-variable.o gcc-python-version.o gcc-python-wrapper.o
autogenerated-callgraph.o autogenerated-cfg.o autogenerated-option.o
autogenerated-function.o autogenerated-gimple.o
autogenerated-location.o autogenerated-parameter.o
autogenerated-pass.o autogenerated-pretty-printer.o
autogenerated-rtl.o autogenerated-tree.o autogenerated-variable.o -o
python.so -lpthread -ldl -lutil -lm -lpython2.7

I went a bit further and tried out another plugin. I downloaded and
built MELT sources and everything runs fine there. These are some nm
outputs for that plugin:

# nm -C $(gcc -print-file-name=plugin/melt.so) | grep -C 5 warning_at
                 U debug_tree(tree_node*)
                 U gt_ggc_m_S(void const*)
00000000000247d0 T melt_apply(meltclosure_st*, melt_un*, char const*,
meltparam_un*, char const*, meltparam_un*)
                 w pragma_lex(tree_node**)
                 U print_node(_IO_FILE*, char const*, tree_node*, int)
                 U warning_at(unsigned int, int, char const*, ...)
                 U fancy_abort(char const*, int, char const*)
                 U fatal_error(char const*, ...)
                 U ggc_collect()
                 U linemap_add(line_maps*, lc_reason, unsigned int,
char const*, unsigned int)
0000000000026560 T meltgc_send(melt_un*, melt_un*, char const*,
meltparam_un*, char const*, meltparam_un*)

** See the correct signature at warning_at

These are my different GCC configurations in x86_64-pc-linux-gnu

# gcc -v
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.7.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-4.7.1/work/gcc-4.7.1/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu
--disable-altivec --disable-fixed-point --with-ppl --with-cloog
--disable-ppl-version-check
--with-cloog-include=/usr/include/cloog-ppl --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --enable-multilib
--with-multilib-list=m32,m64 --enable-libmudflap --disable-libssp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/python
--enable-checking=release --enable-languages=c,c++,java,fortran
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.7.1
p1.0, pie-0.5.3'
Thread model: posix
gcc version 4.7.1 (Gentoo 4.7.1 p1.0, pie-0.5.3)

# gcc-4.6.3 -v
Using built-in specs.
COLLECT_GCC=gcc-4.6.3
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-4.6.3/work/gcc-4.6.3/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu
--disable-altivec --disable-fixed-point --with-ppl --with-cloog
--disable-ppl-version-check
--with-cloog-include=/usr/include/cloog-ppl --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --disable-werror
--enable-secureplt --enable-multilib --enable-libmudflap
--disable-libssp --enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/python
--enable-checking=release --enable-languages=c,c++,java,fortran
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.6.3
p1.0, pie-0.5.1'
Thread model: posix
gcc version 4.6.3 (Gentoo 4.6.3 p1.0, pie-0.5.1)

Any help would be greatly appreciated. Thanks in advance.

David E. Narváez