m4/using_operator.m4

   1 AC_DEFUN([AC_CXX_USING_OPERATOR],
   2   [AC_CACHE_CHECK(
   3       whether compiler supports using ::operator<<,
   4       ac_cv_cxx_using_operator,
   5       [AC_LANG_SAVE
   6        AC_LANG_CPLUSPLUS
   7        AC_TRY_COMPILE([#include <iostream>
   8                        std::ostream& operator<<(std::ostream&, struct s);],
   9                       [using ::operator<<; return 0;],
  10                       ac_cv_cxx_using_operator=1,
  11                       ac_cv_cxx_using_operator=0)
  12       AC_LANG_RESTORE])
  13   if test "$ac_cv_cxx_using_operator" = 1; then
  14     AC_DEFINE(HAVE_USING_OPERATOR, 1, [define if the compiler supports using expression for operator])
  15   fi])