Fix BZ 11420 -- configure uses incorrect link order when testing libpython
Commit Message
Greetings,
https://stackoverflow.com/a/49868387
https://sourceware.org/bugzilla/show_bug.cgi?id=11420
Configure uses "gcc -o conftest -g ... conftest.c -ldl -lncurses -lm -ldl
... -lpthread ... -lpython2.7" when deciding whether give libpython is
usable.
That of course is the wrong link order, and only works for shared libraries
(mostly by accident), and only on some systems.
Attached patch fixes this.
I am not sure about this part of the patch:
- LIBS="$LIBS $new_LIBS"
+ LIBS="$new_LIBS $LIBS"
I think it's always better to prepend new libraries.
Thanks,
2018-04-17 Paul Pluzhnikov <ppluzhnikov@google.com>
PR gdb/11420
* gdb/configure.ac: Prepend libpython.
* gdb/python/python-config.py: Likewise.
* gdb/configure: Regenerate.
Comments
Ping?
> 2018-04-17 Paul Pluzhnikov <ppluzhnikov@google.com>
> PR gdb/11420
> * gdb/configure.ac: Prepend libpython.
> * gdb/python/python-config.py: Likewise.
> * gdb/configure: Regenerate.
On 2018-04-17 11:52, Paul Pluzhnikov via gdb-patches wrote:
> Greetings,
>
> https://stackoverflow.com/a/49868387
> https://sourceware.org/bugzilla/show_bug.cgi?id=11420
>
> Configure uses "gcc -o conftest -g ... conftest.c -ldl -lncurses -lm
> -ldl
> ... -lpthread ... -lpython2.7" when deciding whether give libpython is
> usable.
>
> That of course is the wrong link order, and only works for shared
> libraries
> (mostly by accident), and only on some systems.
>
> Attached patch fixes this.
Hi Paul,
Sorry for letting this slip through the cracks.
It looks like our python-config.py is a (modified) copy of an old
python-config from CPython. A similar bug was reported and fixed
upstream a while ago:
https://bugs.python.org/issue18096
and your fix in python-config.py makes our version closer to the
upstream version, so this part LGTM.
> I am not sure about this part of the patch:
>
> - LIBS="$LIBS $new_LIBS"
> + LIBS="$new_LIBS $LIBS"
>
> I think it's always better to prepend new libraries.
>
> Thanks,
>
> 2018-04-17 Paul Pluzhnikov <ppluzhnikov@google.com>
>
> PR gdb/11420
> * gdb/configure.ac: Prepend libpython.
> * gdb/python/python-config.py: Likewise.
> * gdb/configure: Regenerate.
The configure changes seem good as well, or at worst noops. For
example, in this context, I am wondering if the python_libs value can be
other than empty:
elif test "${have_python_config}" != failed; then
if test "${have_libpython}" = no; then
AC_TRY_LIBPYTHON(python2.7, have_libpython,
${python_includes}, "-lpython2.7 ${python_libs}")
fi
If we are in that context, it's because have_python_config is "no". And
it looks like the only code path that sets have_python_config to "no"
also sets python_libs to empty. If you want to investigate that further
and possibly simplify the code, you are welcome.
I've pushed your patch with these changes:
- Fix pre-existing formatting issue in the python-config.py line
- Re-generate configure (those changes were not included in the patch)
- Remove the gdb/ prefixes in the ChangeLog filenames (they should be
relative to the ChangeLog file itself, which is in gdb/).
Thanks!
Simon
@@ -732,7 +732,7 @@ AC_DEFUN([AC_TRY_LIBPYTHON],
save_CPPFLAGS=$CPPFLAGS
save_LIBS=$LIBS
CPPFLAGS="$CPPFLAGS $new_CPPFLAGS"
- LIBS="$LIBS $new_LIBS"
+ LIBS="$new_LIBS $LIBS"
found_usable_python=no
AC_LINK_IFELSE(AC_LANG_PROGRAM([[#include "Python.h"]],
[[Py_Initialize ();]]),
@@ -922,19 +922,19 @@ else
elif test "${have_python_config}" != failed; then
if test "${have_libpython}" = no; then
AC_TRY_LIBPYTHON(python2.7, have_libpython,
- ${python_includes}, "${python_libs} -lpython2.7")
+ ${python_includes}, "-lpython2.7 ${python_libs}")
fi
if test "${have_libpython}" = no; then
AC_TRY_LIBPYTHON(python2.6, have_libpython,
- ${python_includes}, "${python_libs} -lpython2.6")
+ ${python_includes}, "-lpython2.6 ${python_libs}")
fi
if test ${have_libpython} = no; then
AC_TRY_LIBPYTHON(python2.5, have_libpython,
- ${python_includes}, "${python_libs} -lpython2.5")
+ ${python_includes}, "-lpython2.5 ${python_libs}")
fi
if test ${have_libpython} = no; then
AC_TRY_LIBPYTHON(python2.4, have_libpython,
- ${python_includes}, "${python_libs} -lpython2.4")
+ ${python_includes}, "-lpython2.4 ${python_libs}")
fi
fi
if test "${have_libpython}" = python2.7 -o "${have_libpython}" = python27; then
@@ -58,12 +58,11 @@ for opt in opt_flags:
print (to_unix_path(' '.join(flags)))
elif opt in ('--libs', '--ldflags'):
- libs = []
+ libs = ['-lpython'+pyver + abiflags]
if getvar('LIBS') is not None:
libs.extend(getvar('LIBS').split())
if getvar('SYSLIBS') is not None:
libs.extend(getvar('SYSLIBS').split())
- libs.append('-lpython'+pyver + abiflags)
# add the prefix/lib/pythonX.Y/config dir, but only if there is no
# shared library in prefix/lib/.
if opt == '--ldflags':