From 4e6adefc2b90589aea8ac2c51e0160a2c4d52ed8 Mon Sep 17 00:00:00 2001
From: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Tue, 22 Dec 2020 10:50:12 +0900
Subject: [PATCH] sim: Use c++14 for LIBCXX

The compiler default varies among the environment.
Especially, the default std version for xcode clang doesn't work
for libcxx.

This commit just ensures to use the consistent std version
among compilers.  we can come up with a more sophisticated way
to control the version later if desiable.

clang/macOS (from xcode):

    spacetanuki% c++ -dM -E -x c++ /dev/null | grep __cplusplus
    #define __cplusplus 199711L
    spacetanuki% c++ --version
    Apple clang version 11.0.0 (clang-1100.0.33.17)
    Target: x86_64-apple-darwin18.7.0
    Thread model: posix
    InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
    spacetanuki%

clang/macOS (from homebrew):

    spacetanuki% /usr/local/Cellar/llvm/11.0.0/bin/clang++ -dM -E -x c++ /dev/null | grep __cplusplus
    #define __cplusplus 201402L
    spacetanuki% /usr/local/Cellar/llvm/11.0.0/bin/clang++ --version
    clang version 11.0.0
    Target: x86_64-apple-darwin18.7.0
    Thread model: posix
    InstalledDir: /usr/local/Cellar/llvm/11.0.0/bin
    spacetanuki%

gcc/ubuntu:

    root@477d94753e9b:/# c++ -dM -E -x c++ /dev/null | grep __cplusplus
    #define __cplusplus 201402L
    root@477d94753e9b:/# c++ --version
    c++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
    Copyright (C) 2019 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

    root@477d94753e9b:/#
---
 boards/sim/sim/sim/scripts/Make.defs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/boards/sim/sim/sim/scripts/Make.defs b/boards/sim/sim/sim/scripts/Make.defs
index 22c4835d681..e64b3b5098e 100644
--- a/boards/sim/sim/sim/scripts/Make.defs
+++ b/boards/sim/sim/sim/scripts/Make.defs
@@ -106,6 +106,15 @@ CPPFLAGS := $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS) \
 AFLAGS := $(CFLAGS) -D__ASSEMBLY__
 
 ifeq ($(CONFIG_LIBCXX),y)
+  # Why c++14?
+  #  * libcxx seems to require c++11.
+  #  * The compiler defaults varies:
+  #      clang/macOS (from xcode): 199711L
+  #      gcc/ubuntu:               201402L
+  #  * There is a precedent to use c++14.
+  #    (boards/arm/stm32l4/nucleo-l476rg/scripts/Make.defs)
+  CXXFLAGS += -std=c++14
+
   ifeq ($(CONFIG_HOST_MACOS),y)
     # macOS uses libc++abi
     CXXFLAGS += -DLIBCXX_BUILDING_LIBCXXABI