Issue #21166: Prevent possible segfaults and other random failures of

python --generate-posix-vars in pybuilddir.txt build target by ensuring
that pybuilddir.txt is always regenerated when configure is run and
that the newly built skeleton python does not inadvertently import
modules from previously installed instances.

Makefile.pre.in

@@ -546,8 +546,18 @@ platform: $(BUILDPYTHON) pybuilddir.txt
 # Create build directory and generate the sysconfig build-time data there.
 # pybuilddir.txt contains the name of the build dir and is used for
 # sys.path fixup -- see Modules/getpath.c.
+# Since this step runs before shared modules are built, try to avoid bootstrap
+# problems by creating a dummy pybuildstr.txt just to allow interpreter
+# initialization to succeed.  It will be overwritten by generate-posix-vars
+# or removed in case of failure.
 pybuilddir.txt: $(BUILDPYTHON)
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars
+	@echo "none" > ./pybuilddir.txt
+	$(RUNSHARED) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars ;\
+	if test $$? -ne 0 ; then \
+		echo "generate-posix-vars failed" ; \
+		rm -f ./pybuilddir.txt ; \
+		exit 1 ; \
+	fi
 
 # Build the shared modules
 # Under GNU make, MAKEFLAGS are sorted and normalized; the 's' for

Misc/NEWS

@@ -242,6 +242,9 @@ Build
 
 - Issue #21811: Anticipated fixes to support OS X versions > 10.9.
 
+- Issue #21166: Prevent possible segfaults and other random failures of
+  python --generate-posix-vars in pybuilddir.txt build target.
+
 IDLE
 ----
 

configure

@@ -2950,6 +2950,9 @@ case $host_os in *\ *) host_os=`echo "$host_os" | sed 's/ /-/g'`;; esac
 
 
 
+# pybuilddir.txt will be created by --generate-posix-vars in the Makefile
+rm -f pybuilddir.txt
+
 if test "$cross_compiling" = yes; then
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for python interpreter for cross build" >&5
 $as_echo_n "checking for python interpreter for cross build... " >&6; }

configure.ac

@@ -53,6 +53,9 @@ AC_CANONICAL_HOST
 AC_SUBST(build)
 AC_SUBST(host)
 
+# pybuilddir.txt will be created by --generate-posix-vars in the Makefile
+rm -f pybuilddir.txt
+
 if test "$cross_compiling" = yes; then
     AC_MSG_CHECKING([for python interpreter for cross build])
     if test -z "$PYTHON_FOR_BUILD"; then