From 24a7dd45dcc6c7b4d22bf1dc3762ff27efeedcaa Mon Sep 17 00:00:00 2001
From: Kornel Benko <kornel@lyx.org>
Date: Sat, 11 Jun 2016 12:23:33 +0200
Subject: [PATCH] Cmake build: Determine availability of 'std::regex' if using
 clang compiler

---
 CMakeLists.txt                                | 32 +++++++++++++------
 .../cmake/modules/FindCXX11Compiler.cmake     | 32 +++++++++++++++++--
 2 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index fee89e135c..1bc690a12f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -260,17 +260,29 @@ if(NOT CXX11COMPILER_FOUND)
 endif()
 set(LYX_GCC11_MODE)
 if(UNIX OR MINGW)
-	execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION OUTPUT_STRIP_TRAILING_WHITESPACE)
-	message(STATUS "Using GCC version ${GCC_VERSION}")
-	if(GCC_VERSION VERSION_LESS 4.9)
-		if(GCC_VERSION VERSION_LESS 4.3)
-			message(FATAL_ERROR "gcc >= 4.3 is required.")
-		endif()
-		# <regex> in gcc is unusable in versions less than 4.9.0
-		# see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53631
-		set(LYX_USE_STD_REGEX 0)
+	if (CMAKE_CXX_COMPILER_ID MATCHES "^[cC]lang$")
+	  # ignore the GCC_VERSION for clang
+	  # We pretend the compiler version >= 4.9
+	  message(STATUS "Using clang")
+	  # CXX11_STD_REGEX found in FindCXX11Compiler.cmake
+	  if(CXX11_STD_REGEX)
+	    set(LYX_USE_STD_REGEX 1)
+	  else()
+	    set(LYX_USE_STD_REGEX 0)
+	  endif()
 	else()
-		set(LYX_USE_STD_REGEX 1)
+	  execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION OUTPUT_STRIP_TRAILING_WHITESPACE)
+	  message(STATUS "Using GCC version ${GCC_VERSION}")
+	  if(GCC_VERSION VERSION_LESS 4.9)
+		  if(GCC_VERSION VERSION_LESS 4.3)
+			  message(FATAL_ERROR "gcc >= 4.3 is required.")
+		  endif()
+		  # <regex> in gcc is unusable in versions less than 4.9.0
+		  # see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53631
+		  set(LYX_USE_STD_REGEX 0)
+	  else()
+		  set(LYX_USE_STD_REGEX 1)
+	  endif()
 	endif()
 	set(LYX_GCC11_MODE "${CXX11_FLAG}")
 else()
diff --git a/development/cmake/modules/FindCXX11Compiler.cmake b/development/cmake/modules/FindCXX11Compiler.cmake
index 7d09f8f911..5d127cf6c6 100644
--- a/development/cmake/modules/FindCXX11Compiler.cmake
+++ b/development/cmake/modules/FindCXX11Compiler.cmake
@@ -80,6 +80,26 @@ int main() {
 };
 ")
 
+# The following code snipped taken from example in http://stackoverflow.com/questions/8561850/compile-stdregex-iterator-with-gcc
+set(REGEX_TEST_SOURCE
+"
+#include <regex>
+#include <iostream>
+
+#include <string.h>
+
+typedef std::regex_iterator<const char *> Myiter;
+int main()
+{
+    const char *pat = \"axayaz\";
+    Myiter::regex_type rx(\"a\");
+    Myiter next(pat, pat + strlen(pat), rx);
+    Myiter end;
+
+    return (0);
+}
+")
+
 # check c compiler
 set(SAFE_CMAKE_REQUIRED_QUIET ${CMAKE_REQUIRED_QUIET})
 set(CMAKE_REQUIRED_QUIET ON)
@@ -93,7 +113,15 @@ FOREACH(FLAG ${CXX11_FLAG_CANDIDATES})
     SET(CXX11_FLAG "${FLAG}")
     message(STATUS "CXX11_FLAG_DETECTED = \"${FLAG}\"")
     set(LYX_USE_CXX11 1)
-    BREAK()
+      check_cxx_source_compiles("${REGEX_TEST_SOURCE}" CXX_STD_REGEX_DETECTED)
+      if (CXX_STD_REGEX_DETECTED)
+	message(STATUS "Compiler supports std_regex")
+	set(CXX11_STD_REGEX ON)
+      else()
+	message(STATUS "Compiler does not support std_regex")
+	set(CXX11_STD_REGEX OFF)
+      endif()
+    break()
   ENDIF()
 ENDFOREACH()
 set(CMAKE_REQUIRED_QUIET ${SAFE_CMAKE_REQUIRED_QUIET})
@@ -101,4 +129,4 @@ set(CMAKE_REQUIRED_QUIET ${SAFE_CMAKE_REQUIRED_QUIET})
 # handle the standard arguments for find_package
 FIND_PACKAGE_HANDLE_STANDARD_ARGS(CXX11Compiler DEFAULT_MSG CXX11_FLAG)
 
-MARK_AS_ADVANCED(CXX11_FLAG)
+MARK_AS_ADVANCED(CXX11_FLAG CXX11_STD_REGEX)