Something

# Because of the way Python implements polymorphism, we get the following warning:
# "warning: dereferencing type-punned pointer will break strict-aliasing rules"
# -fno-strict-aliasing (as used in Python build) switches warnings off
NO_STRICT_ALIASING_CFLAGS=""
if test "x$GCC" = "xyes" ; then
  AC_MSG_CHECKING(whether $CC accepts -fno-strict-aliasing)
  ac_save_cc="$CC"
  CC="$CC -fno-strict-aliasing"
  AC_TRY_RUN([int main() { return 0; }],
             ac_cv_no_strict_aliasing_ok=yes,
             ac_cv_no_strict_aliasing_ok=no,
             ac_cv_no_strict_aliasing_ok=no)
  CC="$ac_save_cc"
  AC_MSG_RESULT($ac_cv_no_strict_aliasing_ok)
  if test "x$ac_cv_no_strict_aliasing_ok" = "xyes" ; then
    NO_STRICT_ALIASING_CFLAGS="-fno-strict-aliasing"
  fi
fi
AC_SUBST(NO_STRICT_ALIASING_CFLAGS)