-Wformat is needed by gcc 4.8 (closes #17547)

Misc/NEWS

@@ -95,6 +95,9 @@ Library
 Build
 -----
 
+- Issue #17547: In configure, explicitly pass -Wformat for the benefit for GCC
+  4.8.
+
 - Issue #17682: Add the _io module to Modules/Setup.dist (commented out).
 
 - Issue #17086: Search the include and library directories provided by the

configure

@@ -6253,7 +6253,7 @@ then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether gcc supports ParseTuple __format__" >&5
 $as_echo_n "checking whether gcc supports ParseTuple __format__... " >&6; }
   save_CFLAGS=$CFLAGS
-  CFLAGS="$CFLAGS -Werror"
+  CFLAGS="$CFLAGS -Werror -Wformat"
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 

configure.ac

@@ -1326,7 +1326,7 @@ if test "$GCC" = "yes"
 then
   AC_MSG_CHECKING(whether gcc supports ParseTuple __format__)
   save_CFLAGS=$CFLAGS
-  CFLAGS="$CFLAGS -Werror"
+  CFLAGS="$CFLAGS -Werror -Wformat"
   AC_COMPILE_IFELSE([
     AC_LANG_PROGRAM([[void f(char*,...)__attribute((format(PyArg_ParseTuple, 1, 2)));]], [[]])
   ],[