bpo-45723: Add helpers for save/restore env (GH-29637)

3 files changed, 73 insertions, 41 deletions

diff --git a/Misc/NEWS.d/next/Build/2021-11-19-15-42-27.bpo-45723.vwIJWI.rst b/Misc/NEWS.d/next/Build/2021-11-19-15-42-27.bpo-45723.vwIJWI.rst
new file mode 100644
index 0000000..51e7735
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2021-11-19-15-42-27.bpo-45723.vwIJWI.rst
@@ -0,0 +1,10 @@
+Add ``autoconf`` helpers for saving and restoring environment variables:
+
+* ``SAVE_ENV``: Save ``$CFLAGS``, ``$LDFLAGS``, ``$LIBS``, and
+  ``$CPPFLAGS``.
+* ``RESTORE_ENV``: Restore ``$CFLAGS``, ``$LDFLAGS``, ``$LIBS``, and
+  ``$CPPFLAGS``.
+* ``WITH_SAVE_ENV([SCRIPT])``: Run ``SCRIPT`` wrapped with ``SAVE_ENV`` and
+  ``RESTORE_ENV``.
+
+Patch by Erlend E. Aasland.
diff --git a/configure b/configure
index 7bf2cfb..fd75c52 100755
--- a/configure
+++ b/configure
@@ -2866,6 +2866,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+
 if test "$srcdir" != . -a "$srcdir" != "$(pwd)"; then
     # If we're building out-of-tree, we need to make sure the following
     # resources get picked up before their $srcdir counterparts.
@@ -11085,13 +11086,14 @@ save_CFLAGS=$CFLAGS
 save_CPPFLAGS=$CPPFLAGS
 save_LDFLAGS=$LDFLAGS
 save_LIBS=$LIBS
-CPPFLAGS="$LIBSQLITE3_CFLAGS $CFLAGS"
-LDFLAGS="$LIBSQLITE3_LIBS $LDFLAGS"
 
-ac_fn_c_check_header_mongrel "$LINENO" "sqlite3.h" "ac_cv_header_sqlite3_h" "$ac_includes_default"
+  CPPFLAGS="$LIBSQLITE3_CFLAGS $CFLAGS"
+  LDFLAGS="$LIBSQLITE3_LIBS $LDFLAGS"
+
+  ac_fn_c_check_header_mongrel "$LINENO" "sqlite3.h" "ac_cv_header_sqlite3_h" "$ac_includes_default"
 if test "x$ac_cv_header_sqlite3_h" = xyes; then :
 
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqlite3_open_v2 in -lsqlite3" >&5
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqlite3_open_v2 in -lsqlite3" >&5
 $as_echo_n "checking for sqlite3_open_v2 in -lsqlite3... " >&6; }
 if ${ac_cv_lib_sqlite3_sqlite3_open_v2+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -11129,15 +11131,15 @@ fi
 $as_echo "$ac_cv_lib_sqlite3_sqlite3_open_v2" >&6; }
 if test "x$ac_cv_lib_sqlite3_sqlite3_open_v2" = xyes; then :
 
-    have_sqlite3=yes
-    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+      have_sqlite3=yes
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 
-        #include <sqlite3.h>
-        #if SQLITE_VERSION_NUMBER < 3007015
-        #  error "SQLite 3.7.15 or higher required"
-        #endif
+          #include <sqlite3.h>
+          #if SQLITE_VERSION_NUMBER < 3007015
+          #  error "SQLite 3.7.15 or higher required"
+          #endif
 
 int
 main ()
@@ -11159,7 +11161,7 @@ else
   have_sqlite3=no
 fi
 
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqlite3_load_extension in -lsqlite3" >&5
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqlite3_load_extension in -lsqlite3" >&5
 $as_echo_n "checking for sqlite3_load_extension in -lsqlite3... " >&6; }
 if ${ac_cv_lib_sqlite3_sqlite3_load_extension+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -11211,6 +11213,8 @@ CPPFLAGS=$save_CPPFLAGS
 LDFLAGS=$save_LDFLAGS
 LIBS=$save_LIBS
 
+
+
 # Check for support for loadable sqlite extensions
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for --enable-loadable-sqlite-extensions" >&5
 $as_echo_n "checking for --enable-loadable-sqlite-extensions... " >&6; }
diff --git a/configure.ac b/configure.ac
index e263993..63df518 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,32 @@ m4_ifdef(
     [AC_MSG_ERROR([Please install pkgconf's m4 macro package and re-run autoreconf])]
 )dnl
 
+dnl Helpers for saving and restoring environment variables:
+dnl - _SAVE_VAR([VAR])         Helper for SAVE_ENV; stores VAR as save_VAR
+dnl - _RESTORE_VAR([VAR])      Helper for RESTORE_ENV; restores VAR from save_VAR
+dnl - SAVE_ENV                 Saves CFLAGS, LDFLAGS, LIBS, and CPPFLAGS
+dnl - RESTORE_ENV              Restores CFLAGS, LDFLAGS, LIBS, and CPPFLAGS
+dnl - WITH_SAVE_ENV([SCRIPT])  Runs SCRIPT wrapped with SAVE_ENV/RESTORE_ENV
+AC_DEFUN([_SAVE_VAR], [AS_VAR_COPY([save_][$1], [$1])])dnl
+AC_DEFUN([_RESTORE_VAR], [AS_VAR_COPY([$1], [save_][$1])])dnl
+AC_DEFUN([SAVE_ENV],
+[_SAVE_VAR([CFLAGS])]
+[_SAVE_VAR([CPPFLAGS])]
+[_SAVE_VAR([LDFLAGS])]
+[_SAVE_VAR([LIBS])]
+)dnl
+AC_DEFUN([RESTORE_ENV],
+[_RESTORE_VAR([CFLAGS])]
+[_RESTORE_VAR([CPPFLAGS])]
+[_RESTORE_VAR([LDFLAGS])]
+[_RESTORE_VAR([LIBS])]
+)dnl
+AC_DEFUN([WITH_SAVE_ENV],
+[SAVE_ENV]
+[$1]
+[RESTORE_ENV]
+)dnl
+
 AC_SUBST(BASECPPFLAGS)
 if test "$srcdir" != . -a "$srcdir" != "$(pwd)"; then
     # If we're building out-of-tree, we need to make sure the following
@@ -3174,37 +3200,29 @@ PKG_CHECK_MODULES(
 )
 AS_VAR_APPEND([LIBSQLITE3_CFLAGS], [' -I$(srcdir)/Modules/_sqlite'])
 
+WITH_SAVE_ENV(
 dnl bpo-45774/GH-29507: The CPP check in AC_CHECK_HEADER can fail on FreeBSD,
-dnl hence CPPFLAGS instead of CFLAGS. We still need to save CFLAGS, because it
-dnl is touched by AC_CHECK_HEADER.
-AS_VAR_COPY([save_CFLAGS], [CFLAGS])
-AS_VAR_COPY([save_CPPFLAGS], [CPPFLAGS])
-AS_VAR_COPY([save_LDFLAGS], [LDFLAGS])
-AS_VAR_COPY([save_LIBS], [LIBS])
-CPPFLAGS="$LIBSQLITE3_CFLAGS $CFLAGS"
-LDFLAGS="$LIBSQLITE3_LIBS $LDFLAGS"
-
-AC_CHECK_HEADER([sqlite3.h], [
-  AC_CHECK_LIB([sqlite3], [sqlite3_open_v2], [
-    have_sqlite3=yes
-    AC_COMPILE_IFELSE([
-      AC_LANG_PROGRAM([
-        #include <sqlite3.h>
-        #if SQLITE_VERSION_NUMBER < 3007015
-        #  error "SQLite 3.7.15 or higher required"
-        #endif
-      ], [])
-    ], [have_supported_sqlite3=yes], [have_supported_sqlite3=no])
-  ], [have_sqlite3=no])
-  AC_CHECK_LIB([sqlite3], [sqlite3_load_extension],
-               [have_sqlite3_load_extension=yes],
-               [have_sqlite3_load_extension=no])
-])
-
-AS_VAR_COPY([CFLAGS], [save_CFLAGS])
-AS_VAR_COPY([CPPFLAGS], [save_CPPFLAGS])
-AS_VAR_COPY([LDFLAGS], [save_LDFLAGS])
-AS_VAR_COPY([LIBS], [save_LIBS])
+dnl hence CPPFLAGS instead of CFLAGS.
+  CPPFLAGS="$LIBSQLITE3_CFLAGS $CFLAGS"
+  LDFLAGS="$LIBSQLITE3_LIBS $LDFLAGS"
+
+  AC_CHECK_HEADER([sqlite3.h], [
+    AC_CHECK_LIB([sqlite3], [sqlite3_open_v2], [
+      have_sqlite3=yes
+      AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([
+          #include <sqlite3.h>
+          #if SQLITE_VERSION_NUMBER < 3007015
+          #  error "SQLite 3.7.15 or higher required"
+          #endif
+        ], [])
+      ], [have_supported_sqlite3=yes], [have_supported_sqlite3=no])
+    ], [have_sqlite3=no])
+    AC_CHECK_LIB([sqlite3], [sqlite3_load_extension],
+                 [have_sqlite3_load_extension=yes],
+                 [have_sqlite3_load_extension=no])
+  ])
+)
 
 # Check for support for loadable sqlite extensions
 AC_MSG_CHECKING(for --enable-loadable-sqlite-extensions)