Remove configure test for std::call_once

It was not needed anymore since 193cda6e.

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index 2138a8482ef6a8d27486d4f26182fb472ed2a40c..2d6ceccb838775ab10c443e897a895d4e6d4b3d3 100644 (file)
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -210,32 +210,6 @@ AC_DEFUN([LYX_CXX_CXX11_FLAGS],
 ])
 
 
-dnl Usage: LYX_CXX_USE_CALL_ONCE
-dnl check whether we can use std::call_once and set the
-dnl LYX_USE_STD_CALL_ONCE macro and conditional accordingly.
-AC_DEFUN([LYX_CXX_USE_CALL_ONCE],
-[AC_MSG_CHECKING([for std::call_once availability])
-   save_CPPFLAGS=$CPPFLAGS
-   CPPFLAGS="$AM_CPPFLAGS $CPPFLAGS"
-   save_CXXFLAGS=$CXXFLAGS
-   CXXFLAGS="$AM_CXXFLAGS $CXXFLAGS"
-   AC_LINK_IFELSE([AC_LANG_PROGRAM([[
-       #include <mutex>
-       static std::once_flag flag;
-     ]], [[
-       std::call_once(flag, [](){ return; });
-   ]])],[lyx_std_call_once=yes],[lyx_std_call_once=no])
-   CXXFLAGS=$save_CXXFLAGS
-   CPPFLAGS=$save_CPPFLAGS
-   AC_MSG_RESULT([$lyx_std_call_once])
-
- if test $lyx_std_call_once = yes ; then
-  AC_DEFINE([LYX_USE_STD_CALL_ONCE], 1, [define to 1 if std::call_once is supported by the compiler])
- fi
- AM_CONDITIONAL([LYX_USE_STD_CALL_ONCE], test $lyx_std_call_once = yes)
-])
-
-
 dnl Usage: LYX_LIB_STDCXX: set lyx_cv_lib_stdcxx to yes if the STL library is libstdc++.
 AC_DEFUN([LYX_LIB_STDCXX],
 [AC_CACHE_CHECK([whether STL is libstdc++],
@@ -262,7 +236,6 @@ AC_LANG_PUSH(C++)
 LYX_PROG_CLANG
 LYX_CXX_CXX11_FLAGS($enable_cxx_mode)
 LYX_LIB_STDCXX
-LYX_CXX_USE_CALL_ONCE
 AC_LANG_POP(C++)
 
 ### We might want to get or shut warnings.