From 78cb92f077ee34b57735f93ac080dec6384fd8b4 Mon Sep 17 00:00:00 2001
From: Christian Heimes <christian@python.org>
Date: Wed, 29 Jun 2022 15:03:45 +0200
Subject: [PATCH] gh-94404: Use module CFLAGS before PY_STDMODULE_CFLAGS

``PY_STDMODULE_CFLAGS`` may contain include directories with system
headers. This can break compiling with built-in libmpdec.
---
 Makefile.pre.in                                            | 4 ++--
 .../Build/2022-06-29-08-58-31.gh-issue-94404.3MadM6.rst    | 3 ++-
 Modules/makesetup                                          | 7 ++++---
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 3601d8a8775c69..14e7f6035578be 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -829,7 +829,7 @@ python.worker.js: $(srcdir)/Tools/wasm/python.worker.js
 
 ##########################################################################
 # Build static libmpdec.a
-LIBMPDEC_CFLAGS=$(PY_STDMODULE_CFLAGS) $(CCSHARED) @LIBMPDEC_CFLAGS@
+LIBMPDEC_CFLAGS=@LIBMPDEC_CFLAGS@ $(PY_STDMODULE_CFLAGS) $(CCSHARED)
 
 # for setup.py
 DECIMAL_CFLAGS=@LIBMPDEC_CFLAGS@
@@ -887,7 +887,7 @@ $(LIBMPDEC_A): $(LIBMPDEC_OBJS)
 
 ##########################################################################
 # Build static libexpat.a
-LIBEXPAT_CFLAGS=$(PY_STDMODULE_CFLAGS) $(CCSHARED) @LIBEXPAT_CFLAGS@
+LIBEXPAT_CFLAGS=@LIBEXPAT_CFLAGS@ $(PY_STDMODULE_CFLAGS) $(CCSHARED)
 
 # for setup.py
 EXPAT_CFLAGS=@LIBEXPAT_CFLAGS@
diff --git a/Misc/NEWS.d/next/Build/2022-06-29-08-58-31.gh-issue-94404.3MadM6.rst b/Misc/NEWS.d/next/Build/2022-06-29-08-58-31.gh-issue-94404.3MadM6.rst
index 519a5ce81c980c..c7c47533c54ae2 100644
--- a/Misc/NEWS.d/next/Build/2022-06-29-08-58-31.gh-issue-94404.3MadM6.rst
+++ b/Misc/NEWS.d/next/Build/2022-06-29-08-58-31.gh-issue-94404.3MadM6.rst
@@ -1,2 +1,3 @@
 ``makesetup`` now works around an issue with sed on macOS and uses correct
-CFLAGS for object files that end up in a shared extension.
+CFLAGS for object files that end up in a shared extension. Module CFLAGS
+are used before PY_STDMODULE_CFLAGS to avoid clashes with system headers.
diff --git a/Modules/makesetup b/Modules/makesetup
index a45b7de5215ce5..08303814c8c911 100755
--- a/Modules/makesetup
+++ b/Modules/makesetup
@@ -260,13 +260,14 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 			\$*) ;;
 			*) src='$(srcdir)/'"$srcdir/$src";;
 			esac
+			# custom flags first, PY_STDMODULE_CFLAGS may contain -I with system libmpdec
 			case $doconfig in
-			no)	cc="$cc \$(PY_STDMODULE_CFLAGS) \$(CCSHARED)";;
+			no)	cc="$cc $cpps \$(PY_STDMODULE_CFLAGS) \$(CCSHARED)";;
 			*)
-				cc="$cc \$(PY_BUILTIN_MODULE_CFLAGS)";;
+				cc="$cc $cpps \$(PY_BUILTIN_MODULE_CFLAGS)";;
 			esac
 			# force rebuild when header file or module build flavor (static/shared) is changed
-			rule="$obj: $src \$(MODULE_${mods_upper}_DEPS) \$(PYTHON_HEADERS) Modules/config.c; $cc $cpps -c $src -o $obj"
+			rule="$obj: $src \$(MODULE_${mods_upper}_DEPS) \$(PYTHON_HEADERS) Modules/config.c; $cc -c $src -o $obj"
 			echo "$rule" >>$rulesf
 		done
 		case $doconfig in