Make libc++ optional for iOS and use the right library in the Xcode projects

It seems that using libc++ when building with Xcode 4 (and iOS SDK 6)
you get linking errors. Stick to libstdc++ for now then with that.

Propagate the choice to the iOS Xcode projects through the lo.xcconfig
file.

Change-Id: Ic61dd2336066a77c4219c532106e3e50e85d0689

configure.ac

@@ -2911,6 +2911,7 @@ if test $_os = iOS; then
     for sdkver in 7.0 6.1 6.0; do
         t=$xcode_developer/Platforms/$platform.platform/Developer/SDKs/$platform$sdkver.sdk
         if test -d $t; then
+            ios_sdk=$sdkver
             sysroot=$t
             break
         fi
@@ -2956,9 +2957,27 @@ if test $_os = iOS; then
     # Just add -fvisibility=hidden to CC and CXX directly so that the 3rd-party libs also
     # get compiled with it, to avoid ld warnings when linking all that together into one
     # executable.
-    # Also, use libc++.
+    # Use libc++ if opted in only, and only when building against iOS 7 SDK or newer.
+
+    XCODE_CLANG_CXX_LIBRARY=libstdc++
+    case $ios_sdk in
+    6.*)
+        if test "$enable_libc__" = yes; then
+            AC_MSG_ERROR([--enable-libc++ requires using Xcode 5 and iOS SDK 7 or newer it seems])
+        fi
+        ;;
+    *)
+        if test "$enable_libc__" = yes; then
+            XCODE_CLANG_CXX_LIBRARY=libc++
+        fi
+        ;;
+    esac
+
+    stdlib="-stdlib=$XCODE_CLANG_CXX_LIBRARY"
+
     CC="`xcrun -find clang` -arch $arch -fvisibility=hidden -isysroot $sysroot $lto $versionmin"
-    CXX="`xcrun -find clang++` -arch $arch -fvisibility=hidden -stdlib=libc++ -isysroot $sysroot $lto $versionmin"
+    CXX="`xcrun -find clang++` -arch $arch -fvisibility=hidden $stdlib -isysroot $sysroot $lto $versionmin"
+
     INSTALL_NAME_TOOL=`xcrun -find install_name_tool`
     AR=`xcrun -find ar`
     NM=`xcrun -find nm`
@@ -2967,6 +2986,8 @@ if test $_os = iOS; then
     RANLIB=`xcrun -find ranlib`
 fi
 
+AC_SUBST(XCODE_CLANG_CXX_LIBRARY)
+
 AC_MSG_CHECKING([whether to treat the installation as read-only])
 
 if test \( -z "$enable_readonly_installset" -a "$ENABLE_MACOSX_SANDBOX" = TRUE \) -o \

ios/MobileLibreOffice/MobileLibreOffice.xcodeproj/project.pbxproj

@@ -1510,7 +1510,6 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ARCHS = armv7;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -1555,7 +1554,6 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ARCHS = armv7;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -1592,7 +1590,6 @@
 		689EBB0E18069FB8002F1CD7 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				CLANG_CXX_LIBRARY = "libc++";
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_INPUT_FILETYPE = sourcecode.cpp.objcpp;
 				GCC_PRECOMPILE_PREFIX_HEADER = YES;
@@ -1614,7 +1611,6 @@
 		689EBB0F18069FB8002F1CD7 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				CLANG_CXX_LIBRARY = "libc++";
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_INPUT_FILETYPE = sourcecode.cpp.objcpp;
 				GCC_PRECOMPILE_PREFIX_HEADER = YES;

ios/lo.xcconfig.in

@@ -16,3 +16,8 @@ LO_BUILDDIR = @BUILDDIR@
 LO_INSTDIR = @INSTDIR@
 LO_OUTDIR = @OUTDIR@
 LO_WORKDIR = @WORKDIR@
+
+// These are actual Xcode-known settings. The corresponding autoconf
+// variables are prefixed with XCODE_ to make it clear in configure.ac
+// what they will be used for.
+CLANG_CXX_LIBRARY = @XCODE_CLANG_CXX_LIBRARY@

ios/shared/ios_sharedlo.xcodeproj/project.pbxproj

@@ -459,7 +459,6 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ARCHS = armv7;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -500,7 +499,6 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ARCHS = armv7;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -531,7 +529,6 @@
 		68FDBE3918053A140064DD74 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				CLANG_CXX_LIBRARY = "libc++";
 				DSTROOT = /tmp/ios_sharedlo.dst;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_LINK_WITH_DYNAMIC_LIBRARIES = NO;
@@ -549,7 +546,6 @@
 		68FDBE3A18053A140064DD74 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				CLANG_CXX_LIBRARY = "libc++";
 				DSTROOT = /tmp/ios_sharedlo.dst;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_LINK_WITH_DYNAMIC_LIBRARIES = NO;