clang: Switch c++ default to gnu++14 standard

Using cmdline options -std doesnt always work e.g. boost
where it uses c++ driver (clang++) to invoke compilation
but then passes '-x c' to choose the language for compilation

Which ends in errors like below

error: invalid argument '-std=c++14' not allowed with 'C'

Therefore change the defaults in driver itself to use gnu++14
which is default with g++ from gcc7+ too.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

3 files changed, 30 insertions, 1 deletions

diff --git a/classes/clang.bbclass b/classes/clang.bbclass
index e4b35cf..d527b26 100644
--- a/classes/clang.bbclass
+++ b/classes/clang.bbclass
@@ -1,6 +1,6 @@
 # Add the necessary override
 CC_toolchain-clang  = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
-CXX_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang++ -std=c++14 ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
+CXX_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang++ ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
 CPP_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS} -E"
 CCLD_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
 
diff --git a/recipes-devtools/clang/clang/0008-clang-Default-to-gnu-14-for-c-standard.patch b/recipes-devtools/clang/clang/0008-clang-Default-to-gnu-14-for-c-standard.patch
new file mode 100644
index 0000000..74bfc69
--- /dev/null
+++ b/recipes-devtools/clang/clang/0008-clang-Default-to-gnu-14-for-c-standard.patch
@@ -0,0 +1,28 @@
+From 521fdfcc2031d22b50125b3295b837229c77abd6 Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Sat, 12 Aug 2017 12:56:06 -0700
+Subject: [PATCH 8/8] clang: Default to gnu++14 for c++ standard
+
+GCC 7.x and newer default to same as well
+
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+---
+ lib/Frontend/CompilerInvocation.cpp | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
+index b2c14554a4..eed925fac4 100644
+--- a/lib/Frontend/CompilerInvocation.cpp
++++ b/lib/Frontend/CompilerInvocation.cpp
+@@ -1667,7 +1667,7 @@ void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
+       if (T.isPS4())
+         LangStd = LangStandard::lang_gnucxx11;
+       else
+-        LangStd = LangStandard::lang_gnucxx98;
++        LangStd = LangStandard::lang_gnucxx14;
+       break;
+     case InputKind::RenderScript:
+       LangStd = LangStandard::lang_c99;
+-- 
+2.14.1
+
diff --git a/recipes-devtools/clang/common.inc b/recipes-devtools/clang/common.inc
index f5e7acb..3846a1f 100644
--- a/recipes-devtools/clang/common.inc
+++ b/recipes-devtools/clang/common.inc
@@ -18,6 +18,7 @@ CLANGPATCHES = "\
     file://0004-clang-Prepend-trailing-to-sysroot.patch;patchdir=tools/clang \
     file://0005-clang-Look-inside-the-target-sysroot-for-compiler-ru.patch;patchdir=tools/clang \
     file://0006-clang-Define-releative-gcc-installation-dir.patch;patchdir=tools/clang \
+    file://0008-clang-Default-to-gnu-14-for-c-standard.patch;patchdir=tools/clang \
 "
 CLANGPATCHES += "${@'file://0007-clang-Enable-SSP-and-PIE-by-default.patch;patchdir=tools/clang' if '${GCCPIE}' else ''}"