背景
因为之前一直在研究jdk源码,但是基于自己比较懒的缘故，一直没有手动编译过jdk源码，也就只是看看书本上的东西，似懂非懂的看懂了也就草草了事了，这次终于下定决心编译一把openJDK8的源码
基础环境
macos High Sierra 10.13.1
openJDK 8
编译
直接找到 http://hg.openjdk.java.net/ ,执行以下命令
# 安装mercurial
brew install mercurial
# clone openJDK源码
hg clone http://hg.openjdk.java.net/jdk8/jdk8 openjdk8
当然在git JDK也有对应的JDK源码，git clone之后checkout到对应的tag上进行编译也是可以的
git clone https://github.com/openjdk/jdk
git checkout -b openjdk8 jdk8-b80
注意如果是用hg clone的方式我们还得执行sh ./get_source.sh命令来获取额外的文件,对于Mercurial和Git的区别，网上一大堆，网友可以自行查找,操作方式可以参考hg git 操作
我们这里选择hg clone的方式，执行
cd openjdk8 && sh ./get_source.sh
安装依赖
brew install freetype
Running Configure
bash ./configure --with-debug-level=slowdebug --with-boot-jdk=/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home --with-freetype-include=/usr/local/Cellar/freetype/2.10.4/include/freetype2 --with-freetype-lib=/usr/local/Cellar/freetype/2.10.4/lib --with-target-bits=64 --with-jvm-variants=server --with-jdk-variant=normal --with-milestone=internal --with-num-cores=2 --with-jobs=4 CC=clang CXX=clang++
其中，
| 名词 | 说明 |
|---|---|
| --with-debug-level | 可选release[默认值], fastdebug, slowdebug slowdebug 含有最丰富的调试信息 |
| --with-boot-jdk | 用于bootstrap build,指向本地已有的jdk |
| --with-freetype-include | freetype include文件目录 |
| --with-freetype-lib | freetype lib目录 |
| --with-target-bits | 编译成64还是32位jdk |
| --with-jvm-variants | jvm 的模式如server,client,kernel等，多个用逗号分开 |
| --with-jdk-variant | jdk的模式,会在build目录下生成的文件下有体现 |
| --with-milestone | build的里程碑，也就是阶段,会在build目录下生成的文件下有体现 |
| --with-num-cores | 用于此次build的核数 |
| --with-jobs | build的并发任务数 |
| CC | C 编译器命令，如：clang，gcc |
| CXX | C++编译器命令，如：clang++，g++ |
关于clang和gcc的区别，参考clang和gcc的区别
make编译
执行如下命令：
make COMPILER_WARNINGS_FATAL=false LFLAGS='-Xlinker -lstdc++' CC=clang USE_CLANG=true LP64=1
其中,
| 名词 | 解释 |
|---|---|
| COMPILER_WARNINGS_FATAL | 设置为false来跳过严格的编译器的语法检查 |
| LFLAGS | 链接时使用的参数 |
| CC | C编译器命令 |
| LP64 | 使用64位数据模型 |
编译的过程出现如下问题，以及解决：
- 修改relocInfo.hpp的367行（hotspot/src/share/vm/code/relocInfo.hpp），没验证为啥需要修改
修改前:
inline friend relocInfo prefix_relocInfo(int datalen=0);
修改后:
inline friend relocInfo prefix_relocInfo(int datalen)
- 修改generated-configure.sh的20061和21640行（common/autoconf/generated-configure.sh），解决configure: error: GCC compiler is required 错误
修改前：
as_fn_error $? "GCC compiler is required. Try setting --with-tools-dir." "$LINENO" 6
as_fn_error $? "GCC compiler is required. Try setting --with-tools-dir." "$LINENO" 5
修改后：
# as_fn_error $? "GCC compiler is required. Try setting --with-tools-dir." "$LINENO" 6
# as_fn_error $? "GCC compiler is required. Try setting --with-tools-dir." "$LINENO" 5
- 修改hotspot/src/share/vm/opto/loopPredicate.cpp 755行，解决error: ordered comparison between pointer and zero ('const TypeInt *' and 'int')
修改前：
assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() ->_lo >= 0, "must be");
修改后：
// assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() ->_lo >= 0, "must be");
- 安装XQuartz，解决'X11/Xlib.h' file not found
安装详细信息见关于 Mac 版 X11,意思即使Mac 不再随附 X11，得自己手动安装,安装完后做软连：ln -s /opt/X11/include/X11 /usr/local/include/X11
如果build成功则会出现：
----- Build times -------
Start 2020-11-24 14:18:38
End 2020-11-24 14:18:50
00:00:01 corba
00:00:06 hotspot
00:00:00 jaxp
00:00:00 jaxws
00:00:02 jdk
00:00:01 langtools
00:00:12 TOTAL
-------------------------
Finished building OpenJDK for target 'default'
验证
build/macosx-x86_64-normal-server-slowdebug/jdk/bin/java -version
居然报错，what??? s s s
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGILL (0x4) at pc=0x000000010f1ed218, pid=74259, tid=6915
#
# JRE version: OpenJDK Runtime Environment (8.0) (build 1.8.0-internal-debug-ljh_2020_11_23_23_19-b00)
# Java VM: OpenJDK 64-Bit Server VM (25.0-b70-debug mixed mode bsd-amd64 compressed oops)
# Problematic frame:
# V [libjvm.dylib+0x9ed218] PerfData::~PerfData()+0x8
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
#
修改hotspot/src/share/vm/runtime/perfData.cpp 285行，此处参考了stackoverflow和简书
修改前：
delete p;
修改后：
// delete p;
之后执行make clean再重新编译，
再重新执行
build/macosx-x86_64-normal-server-slowdebug/jdk/bin/java -version
openjdk version "1.8.0-internal-debug"
OpenJDK Runtime Environment (build 1.8.0-internal-debug-ljh_2020_11_24_11_02-b00)
OpenJDK 64-Bit Server VM (build 25.0-b70-debug, mixed mode)
至此，openJDK8在macOS上的编译完成,具体编译的步骤在源码REDAME中
