背景
因为之前始终在钻研 jdk 源码, 然而基于本人比拟懒的缘故，始终没有手动编译过 jdk 源码，也就只是看看书本上的货色，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
根底环境
macos High Sierra 10.13.1
openJDK 8
编译
间接找到 http://hg.openjdk.java.net/ , 执行以下命令
# 装置 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 上进行编译也是能够的
git clone https://github.com/openjdk/jdk
git checkout -b openjdk8 jdk8-b80留神如果是用 hg clone 的形式咱们还得执行 sh ./get_source.sh 命令来获取额定的文件, 对于 Mercurial 和 Git 的区别，网上一大堆，网友能够自行查找, 操作形式能够参考 hg git 操作
咱们这里抉择 hg clone 的形式，执行
cd openjdk8 && sh ./get_source.sh装置依赖
brew install freetypeRunning 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 | 阐明 |
|---|---|
| –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，多个用逗号离开 |
| –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 的并发工作数 |
| CC | C 编译器命令，如：clang，gcc |
| CXX | C++ 编译器命令，如：clang++，g++ |
对于 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查看 |
| LFLAGS | 链接时应用的参数 |
| CC | C 编译器命令 |
| LP64 | 应用 64 位数据模型 |
编译的过程呈现如下问题，以及解决：
- 批改 relocInfo.hpp 的 367 行（hotspot/src/share/vm/code/relocInfo.hpp），没验证为啥须要批改
批改前:
inline friend relocInfo prefix_relocInfo(int datalen=0);批改后:
inline friend relocInfo prefix_relocInfo(int datalen)- 批改 generated-configure.sh 的 20061 和 21640 行（common/autoconf/generated-configure.sh），解决 configure: error: GCC compiler is required 谬误
批改前：
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批改后：
# 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- 批改 hotspot/src/share/vm/opto/loopPredicate.cpp 755 行，解决 error: ordered comparison between pointer and zero (‘const TypeInt *’ and ‘int’)
批改前：
assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() ->_lo >= 0, "must be");批改后：
// assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() ->_lo >= 0, "must be");-
装置 XQuartz，解决 ’X11/Xlib.h’ file not found
装置详细信息见对于 Mac 版 X11, 意思即便 Mac 不再随附 X11，得本人手动装置, 装置完后做软连：ln -s /opt/X11/include/X11 /usr/local/include/X11
如果 build 胜利则会呈现：
----- 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竟然报错，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 #```
批改 hotspot/src/share/vm/runtime/perfData.cpp 285 行，此处参考了 [stackoverflow](https://stackoverflow.com/questions/50678467/building-openjdk-9-on-mac-os/54954805#54954805) 和[简书](https://www.jianshu.com/p/34c8a8c37169)
批改前：delete p;
批改后：// delete p;` 之后执行 make clean 再从新编译，
再从新执行
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 上的编译实现, 具体编译的步骤在源码 REDAME 中