From 983df8688d6add6d7f35388eac97d5ecd1c8017f Mon Sep 17 00:00:00 2001
From: Ned Deily <nad@acm.org>
Date: Fri, 22 Aug 2014 13:30:59 -0700
Subject: [PATCH] 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 | 12 +++++++++++-
 Misc/NEWS       |  3 +++
 configure       |  3 +++
 configure.ac    |  3 +++
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 80a09269e6..c3568366e1 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -447,8 +447,18 @@ 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
diff --git a/Misc/NEWS b/Misc/NEWS
index cbe93b11e3..b8dab3067d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -120,6 +120,9 @@ Build
 - Issue #15759: "make suspicious", "make linkcheck" and "make doctest" in Doc/
   now display special message when and only when there are failures.
 
+- Issue #21166: Prevent possible segfaults and other random failures of
+  python --generate-posix-vars in pybuilddir.txt build target.
+
 Windows
 -------
 
diff --git a/configure b/configure
index 2c1c82d815..4a698f352a 100755
--- a/configure
+++ b/configure
@@ -2857,6 +2857,9 @@ 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; }
diff --git a/configure.ac b/configure.ac
index 54f8c0f69f..16da9f3999 100644
--- a/configure.ac
+++ b/configure.ac
@@ -16,6 +16,9 @@ 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
-- 
2.50.1