dnl the return type is 'char *', not 'int'.
AC_CACHE_CHECK([whether ttyname_r is compatible with its POSIX signature],
[gl_cv_func_ttyname_r_posix],
dnl the return type is 'char *', not 'int'.
AC_CACHE_CHECK([whether ttyname_r is compatible with its POSIX signature],
[gl_cv_func_ttyname_r_posix],