Bug 30368 - GDB Python Failing to Import Zlib Module
Summary: GDB Python Failing to Import Zlib Module
Status: NEW
Alias: None
Product: gdb
Classification: Unclassified
Component: build (show other bugs)
Version: HEAD
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
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Depends on:
Blocks:
 
Reported: 2023-04-17 21:29 UTC by Justin Chen
Modified: 2026-01-26 18:37 UTC (History)
1 user (show)

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Last reconfirmed: 2023-08-28 00:00:00
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Description Justin Chen 2023-04-17 21:29:17 UTC
When compiling GDB for a non-native target, in my case x86_64 host and aarch64 target, it fails to import zlib when python library is statically linked.

(gdb) python
>import zlib
>print("hello world")
>end
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: /local/users/jc957059/gcc123/build/opt/toolchains/python-runtime/lib/python3.10/lib-dynload/zlib.cpython-310-x86_64-linux-gnu.so: undefined symbol: PyExc_MemoryError
Error while executing Python code.
(gdb) exit

The python library is being statically linked to gdb, but the symbols are not being exported. Thus the PyExc_MemoryError symbol is missing when trying to import zlib.

Looking at this in gdb/configure:21954
# Work around Python http://bugs.python.org/issue10112.  See also
# http://bugs.python.org/issue11410, otherwise -Wl,--dynamic-list has
# no effect.  Note that the only test after this that uses Python is
# the -rdynamic/-Wl,--dynamic-list test, and we do want that one to be
# run without -export-dynamic too.
PYTHON_LIBS=`echo $PYTHON_LIBS | sed -e 's/-Xlinker -export-dynamic//'`

We remove -export-dynamic and expect to add -rdynamic/--dynamic-list. However this is only added for native builds using configure.nat.
gdb/configure:29677
# Import nat definitions.
nat_makefile_frag=/dev/null
if test "${gdb_native}" = "yes"; then
  . ${srcdir}/configure.nat
  nativefile=$NAT_FILE
fi

gdb/configure.nat:54
case ${gdb_host} in
    *linux*)
...
       LOADLIBES='-ldl $(RDYNAMIC)'

I don't see this error for native builds since the -rdynamic flag is present during linking, but for non-native builds this fails. Shouldn't we be adding the -rdynamic flag for all builds? Manually setting LDFLAGS="-rdynamic" fixes this problem for me.

uname -a:
Linux stbirv-lnx-1 5.15.0-46-generic #49-Ubuntu SMP Thu Aug 4 18:03:25 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

gcc -v:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 11.3.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-11 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-11-xKiWfi/gcc-11-11.3.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-xKiWfi/gcc-11-11.3.0/debian/tmp-gcn/usr --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)

Thanks,
Justin
Comment 1 Tom Tromey 2023-08-28 17:44:04 UTC
Internally at AdaCore, we build gdb against a static libpython.
Our build setup seems to add -export-dynamic to LDFLAGS
to make this work.
I think a clean patch to do this in gdb somewhere would
be totally fine.
Comment 2 Tom Tromey 2026-01-26 18:37:45 UTC
Seems like more of a 'build' component thing than 'gdb' or 'python'.