bpo-36361: Generate correct pyconfig.h when cross-compiling

Makefile.pre.in

@@ -1725,6 +1725,7 @@ clean: pycremoval
 	-rm -f Lib/lib2to3/*Grammar*.pickle
 	-rm -f Programs/_testembed Programs/_freeze_importlib
 	-find build -type f -a ! -name '*.gc??' -exec rm -f {} ';'
+	-rm -rf build/run_ifelse_cvs
 	-rm -f Include/pydtrace_probes.h
 	-rm -f profile-gen-stamp
 

Misc/NEWS.d/next/Build/2019-03-19-10-35-38.bpo-36361.WINBB9.rst

@@ -0,0 +1,10 @@
+When cross-compiling and the ``CONFIG_SITE`` environment variable is unset
+or empty, ``configure`` copies the executables, results of the build of the
+AC_RUN_IFELSE test programs in configure.ac, to the ``build/run_ifelse_cvs``
+directory. The ``Misc/build_config_site.sh`` script may be run then to
+create a config.site file when invoked with one of the parameters as a path
+to a shell script that transfers an executable to the platform, target of
+the cross-compilation, and runs it on this platform.  A second run of
+'configure' with the CONFIG_SITE environment variable set to the
+**absolute** path of this config.site file allows configuring the Python
+build with the correct cache values for this platform.

Misc/build_config_site.sh

@@ -0,0 +1,114 @@
+#! /bin/sh
+#
+# Build a config.site file using the executables created in the
+# 'build/run_ifelse_cvs' directory by configure when cross-compiling.
+#
+# The first parameter must be a shell script that takes an executable file
+# pathname as its only parameter. The script uploads the executable and runs it
+# on the host machine, target of the cross-compilation.
+#
+# The config.site file is a shell script that sets the correct cache values
+# for the cross-compilation. It must be used in a second run of configure
+# where the environment variable 'CONFIG_SITE' is set to the config.site
+# **absolute pathname** (autoconf manual, section 15.8 Setting Site Defaults).
+
+usage ()
+{
+    test -n "$1" && { echo $1; echo; } 1>&2
+
+    echo "usage: $pgm push_exec targetdir config_site
+
+  push_exec   Path of the shell script used for uploading the executable on
+              the machine, target of the cross-compilation, and that exits with
+              the exit status of running this executable on this machine.
+
+  targetdir   Directory (possibly out of source) where python is being
+              cross compiled. The executables and their actions generated by
+              configure are located in sub-directories of the
+              build/run_ifelse_cvs sub-directory of 'targetdir'.
+
+  config_site Path of the config.site file generated by $pgm.
+" 1>&2
+    exit 2
+}
+
+# List directory content sorted by modification time, oldest first.
+list_dir_mtime()
+{
+    local list=""
+    for arg in `ls -t $1`
+    do
+        list="$arg $list"
+    done
+    echo "$list"
+}
+
+# Initialize variables.
+pgm=${0##*/}
+test "$#" != 3 && usage
+test ! -f $1 && usage "error: file '$1' does not exist"
+push_exec=$1
+build_dir=$2/build/run_ifelse_cvs
+test ! -d $build_dir && usage "error: directory '$build_dir' does not exist"
+config_site=$3
+
+# First write the list of cache values to config.site.
+cv_list=`echo "$(ls $build_dir)" | sed -n -e 's/^\(.*\)$/#    \1/p'`
+cat << EOF > $config_site
+# This script has been generated by $pgm from the following
+# list of cache values handled by AC_RUN_IFELSE macros as found
+# in configure.ac:
+#
+$cv_list
+#
+# The list may be used to verify that this config.site file has not become
+# stale in the case of addition of new cache values in configure.ac.
+#
+# The script sets the following cache values that have been found different
+# from the pessimistic default values set by AC_RUN_IFELSE, after running the
+# executable on the target machine:
+
+EOF
+
+# The tests for the cache variables are run in the same chronological order
+# as those run by configure.
+ac_cv_pthread_is_default=no
+for cv in `list_dir_mtime $build_dir`; do
+    echo -n "$cv... "
+
+    # Do not run the tests for the cache variables that are not tested
+    # by configure when the ac_cv_pthread_is_default value as been found
+    # as 'yes'.
+    if test $ac_cv_pthread_is_default = yes; then
+        case $cv in
+            ac_cv_kpthread|ac_cv_kthread|ac_cv_pthread)
+                echo "no change, ac_cv_pthread_is_default=$ac_cv_pthread_is_default"
+                continue;;
+        esac
+    fi
+
+    # Run the test.
+    result=FALSE
+    if test -f $build_dir/$cv/a.out && \
+            `/bin/sh $push_exec $build_dir/$cv/a.out`; then
+        result=TRUE
+    fi
+
+    # Add the cache value to config.site if the test result is different from
+    # the content of ACTION-IF-CROSS-COMPILING.
+    if cmp -s $build_dir/$cv/$result $build_dir/$cv/CROSS-COMPILING; then
+        echo "no change"
+    else
+        # Check that the result can be run as a script before adding
+        # it to config.site.
+        if `/usr/bin/env -i /bin/sh $build_dir/$cv/$result`; then
+            echo "using ACTION-IF-$result"
+            cat $build_dir/$cv/$result >> $config_site
+            if test $cv = ac_cv_pthread_is_default -a $result = TRUE; then
+                ac_cv_pthread_is_default=yes
+            fi
+        else
+            echo "error: invalid shell statements in ACTION-IF-$result" 1>&2
+        fi
+    fi
+done

aclocal.m4

@@ -290,3 +290,4 @@ AS_VAR_IF([$1], [""], [$5], [$4])dnl
 
 m4_include([m4/ax_c_float_words_bigendian.m4])
 m4_include([m4/ax_check_openssl.m4])
+m4_include([m4/ac_run_ifelse.m4])