在 Mac OS Catalina 中编译 hadoop 原生库。错误：未知类型名称“constexpr”。别名声明是 C++11 扩展

Question

我正在尝试在 Unix 中编译 Hadoop 本地库，这就是我正在使用的：

1. Hadoop：分支 3.2 (here is the Hadoop Repository)
2. macOS：Catalina 版本 10.15.5
3. Protobuf：libprotoc 2.5.0
4. OpenSSL 1.0.2t 2019 年 9 月 10 日
5. gcc：Apple clang 版本 11.0.3 (clang-1103.0.32.62) 目标：x86_64-apple-darwin19.5.0 线程模型：posix InstalledDir：/Library/Developer/CommandLineTools/usr/bin
6. java 版本“1.8.0_251”（内部版本 1.8.0_251-b08）

我按照这里的所有步骤操作：Compiling Hadoop on MAC 在修复了 openssl 和 protobuf 的几个问题后，现在看起来 Apache Hadoop MapReduce NativeTask 的编译由于与 C++11 的依赖关系而失败。

我是否需要以某种方式指定将 CXXFLAGS 参数设置为 -std=c++11？我该怎么做？还是我的 gcc 中缺少一些配置？

我尝试为 gcc 设置一个别名，然后立即使用标志调用它，就像这里解释的那样：How to make clang support C++ 11 by default，但仍然不起作用。

到目前为止，这些是我遇到的许多类似错误之一：

[WARNING] /usr/local/include/snappy-stubs-public.h:61:16: warning: alias declarations are a C++11 extension [-Wc++11-extensions]

[WARNING] using uint64 = std::uint64_t;

[WARNING] In file included from /Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/test/TestCompressions.cc:29:

[WARNING] /usr/local/include/snappy.h:197:10: error: unknown type name 'constexpr'

[WARNING]   static constexpr int kBlockLog = 16;

[INFO] Apache Hadoop MapReduce NativeTask ................. FAILURE [  1.995 s]

在仔细阅读输出后，我认为这是最终引发错误的命令：

[WARNING] /Library/Developer/CommandLineTools/usr/bin/make  -f CMakeFiles/nttest.dir/build.make CMakeFiles/nttest.dir/build
[WARNING] [ 75%] Building CXX object CMakeFiles/nttest.dir/main/native/test/TestCompressions.cc.o
[WARNING] /Library/Developer/CommandLineTools/usr/bin/c++   -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/target/native/javah -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/src -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/src/util -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/src/lib -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/test -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src -I/Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/target/native -I/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/include/darwin -I/usr/local/include -isystem /Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/../../../../hadoop-common-project/hadoop-common/src/main/native/gtest/include  -g -O2 -Wall -pthread -D_FILE_OFFSET_BITS=64 -DNDEBUG -DSIMPLE_MEMCPY -fno-strict-aliasing -fsigned-char -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk   -o CMakeFiles/nttest.dir/main/native/test/TestCompressions.cc.o -c /Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/test/TestCompressions.cc
[WARNING] In file included from /Users/josh/Dev/hadoop/repo/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/native/test/TestCompressions.cc:29:
[WARNING] In file included from /usr/local/include/snappy.h:45:
[WARNING] /usr/local/include/snappy-stubs-public.h:54:14: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
[WARNING] using int8 = std::int8_t;

谢谢！

Answer 1

我也很难在 OSX 上使用 clang 构建 hadoop-native 库。改用gcc 10 时我取得了更大的成功。

首先使用自制软件安装：

brew install gcc

这应该将gcc 二进制文件放在路径中，但它们将是gcc-10、g++-10 等。所以设置一些环境魔法应该让CMake 使用这些而不是内置的clang 二进制文件：

export CC=$(which gcc-10)
export CXX=$(which g++-10)
export CPP=$(which cpp-10)
export LD=$(which gcc-10)