From 2d49342ce39a2f6177ce8f460d454932f4c90bc2 Mon Sep 17 00:00:00 2001
From: Kornel Benko <kornel@lyx.org>
Date: Sun, 7 Aug 2016 11:32:53 +0200
Subject: [PATCH] Cmake build: Amend 41e409f8: Use std::call_once only if it is
 actually available

---
 development/cmake/ConfigureChecks.cmake | 11 +++++++++++
 development/cmake/config.h.cmake        |  3 +++
 2 files changed, 14 insertions(+)

diff --git a/development/cmake/ConfigureChecks.cmake b/development/cmake/ConfigureChecks.cmake
index 146330a56a..61190c8655 100644
--- a/development/cmake/ConfigureChecks.cmake
+++ b/development/cmake/ConfigureChecks.cmake
@@ -184,6 +184,17 @@ check_cxx_source_compiles(
   "
 HAVE_DEF_MAKE_UNIQUE)
 
+check_cxx_source_compiles(
+  "
+  #include <mutex>
+  static std::once_flag flag;
+  int main() {
+    std::call_once(flag, [](){ return; });
+    return(0);
+  }
+  "
+LYX_USE_STD_CALL_ONCE)
+
 set(USE_LLVM_LIBCPP)
 set(STD_STRING_USES_COW)
 set(USE_GLIBCXX_CXX11_ABI)
diff --git a/development/cmake/config.h.cmake b/development/cmake/config.h.cmake
index 95148b61e7..dbd2c83bc7 100644
--- a/development/cmake/config.h.cmake
+++ b/development/cmake/config.h.cmake
@@ -91,6 +91,9 @@ ${Include_used_spellchecker}
 
 #cmakedefine HAVE_DEF_MAKE_UNIQUE 1
 
+// Define to 1 if std::call_once is supported by the compiler
+#cmakedefine LYX_USE_STD_CALL_ONCE 1
+
 #endif // config.h guard