cross: wrong interpreter returned when no python available #88228

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1. vfazio commented on May 6, 2021

   

   vfaziomannequin

   on May 6, 2021

   MannequinAuthor

   More actions

   When trying to cross compile python3.9, configure attempts to find a strict python 3.9 version match, however if it fails it still attempts to use python in PYTHON_FOR_BUILD instead of failing outright like the code implies it should

   $/python3/targetbuild# which python3.9 python3 python
   /usr/bin/python3

   $/python3/targetbuild# python3 --version
   Python 3.7.3

   $/python3/targetbuild# PYTHON_FOR_REGEN=/python3/hostbuild/python \
   ac_cv_file__dev_ptmx=yes \
   ac_cv_file__dev_ptc=no \
   ac_cv_buggy_getaddrinfo=no \
   ../configure --build=x86-linux-gnu \
   --host=aarch64-linux-gnu \
   --enable-loadable-sqlite-extensions \
   --enable-option-checking=fatal \
   --enable-shared \
   --with-system-expat \
   --with-system-ffi \
   --without-ensurepip
   checking build system type... x86-unknown-linux-gnu
   checking host system type... aarch64-unknown-linux-gnu
   checking for python3.9... /python3/hostbuild/python
   checking for python interpreter for cross build... python
   ...

   $/python3/targetbuild# grep PYTHON_FOR_BUILD config.log
   PYTHON_FOR_BUILD='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pybuilddir.txt && echo $(abs_builddir)/cat pybuilddir.txt:)$(srcdir)/Lib PYTHON_SYSCONFIGDATA_NAME=sysconfigdata$(ABIFLAGS)$(MACHDEP)$(MULTIARCH) python'

   in configure

   if test "$cross_compiling" = yes; then
   AC_MSG_CHECKING([for python interpreter for cross build])
   if test -z "$PYTHON_FOR_BUILD"; then
   for interp in python$PACKAGE_VERSION python3 python; do
   which $interp >/dev/null 2>&1 || continue
   if $interp -c "import sys;sys.exit(not '.'.join(str(n) for n in sys.version_info@<:@:2@:>@) == '$PACKAGE_VERSION')"; then
   break
   fi
   interp=
   done
   if test x$interp = x; then
   AC_MSG_ERROR([python$PACKAGE_VERSION interpreter not found])
   fi
   AC_MSG_RESULT($interp)
   PYTHON_FOR_BUILD='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pybuilddir.txt && echo $(abs_builddir)/cat pybuilddir.txt:)$(srcdir)/Lib PYTHON_SYSCONFIGDATA_NAME=sysconfigdata$(ABIFLAGS)$(MACHDEP)$(MULTIARCH) '$interp
   fi
   elif test "$cross_compiling" = maybe; then
   AC_MSG_ERROR([Cross compiling required --host=HOST-TUPLE and --build=ARCH])
   else
   PYTHON_FOR_BUILD='./$(BUILDPYTHON) -E'
   fi
   AC_SUBST(PYTHON_FOR_BUILD)

   The issue is a failing edge case here:

       for interp in python$PACKAGE_VERSION python3 python; do
           which $interp >/dev/null 2>&1 || continue
   

   where interp keeps it's last value doesn't trigger the empty check here:

       if test x$interp = x; then
           AC_MSG_ERROR([python$PACKAGE_VERSION interpreter not found])
       fi
   

   Note that there's an explicit clearing of interp when the python version isn't a match:

               if $interp -c "import sys;sys.exit(not '.'.join(str(n) for n in sys.version_info@<:@:2@:>@) == '$PACKAGE_VERSION')"; then
                   break
               fi
               interp=

   The fix should be pretty straightforward:

       for interp in python$PACKAGE_VERSION python3 python ''; do
   

   adding '' as the last possible interpreter means one hasn't been found up to that point and allows configure to properly fail

   $/python3/targetbuild# PYTHON_FOR_REGEN=/python3/hostbuild/python ac_cv_file__dev_ptmx=yes ac_cv_file__dev_ptc=no ac_cv_buggy_getaddrinfo=no ../configure --build=x86-linux-gnu --host=aarch64-linux-gnu --enable-loadable-sqlite-extensions --enable-option-checking=fatal --enable-shared --with-system-expat --with-system-ffi --without-ensurepip
   checking build system type... x86-unknown-linux-gnu
   checking host system type... aarch64-unknown-linux-gnu
   checking for python3.9... /python3/hostbuild/python
   checking for python interpreter for cross build... configure: error: python3.9 interpreter not found

   It will continue to work when a proper interpreter is found

   $/python3/targetbuild# PATH=/python3/hostbuild:$PATH PYTHON_FOR_REGEN=/python3/hostbuild/python ac_cv_file__dev_ptmx=yes ac_cv_file__dev_ptc=no ac_cv_buggy_getaddrinfo=no ../configure --build=x86-linux-gnu --host=aarch64-linux-gnu --enable-loadable-sqlite-extensions --enable-option-checking=fatal --enable-shared --with-system-expat --with-system-ffi --without-ensurepip
   checking build system type... x86-unknown-linux-gnu
   checking host system type... aarch64-unknown-linux-gnu
   checking for python3.9... /python3/hostbuild/python
   checking for python interpreter for cross build... Could not find platform dependent libraries <exec_prefix>
   Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
   python

   This should help highlight any inconsistent environment between configuring and building.
2. vfazio

   added

   3.9 (EOL)end of lifeend of life

   3.10 (EOL)end of lifeend of life

   3.11only security fixesonly security fixes

   buildThe build process and cross-buildThe build process and cross-build

   on May 6, 2021
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. vfazio commented on Apr 11, 2022

   

   vfazio

   on Apr 11, 2022

   ContributorAuthor

   More actions

   This should probably be closed in favor of #90039 which was merged in #29835.

   It's still an issue for versions prior to 3.11