编译OpenJDK12实战

跟着深入理解jvm3一书中实战操作，自编译JDK12

下载源码

直接下载zip（不推荐）

原书从官网源码下载（不推荐

GItHub仓库（推荐）

推荐直接GitHub拉（最近clone的速度快了挺多），大概两三分钟就clone完毕。直接clone到的是JDK最新版本，详解看 进行编译 第2步。

git clone https://github.com/openjdk/jdk

系统

我用的和书中一样的ubuntu18，我的是Ubuntu 18.04.6 LTS x86_64

构建编译环境

1. 依赖

   sudo apt-get install build-essential

2. 安装OpenJDK 11。要编译大版本为N的JDK，要另外准备一个大版本号至少为N-1的、已编译好的JDK。

   sudo apt-get install openjdk-11-jdk

进行编译

1. 获取编译参数帮助

   bash configure --help

   我这里因为没有安装autoconf会报一个错误Error: Cannot find autoconf，遂安装后再执行获取help即可

   sudo apt-get install autoconf

2. 配置

   编译FastDebug版、仅含Server模式的HotSpot虚拟机

   bash configure --enable-debug --with-jvm-variants=server

   在我的ubuntu环境执行配置命令，接收到以下错误

   configure: (Your Boot JDK version must be one of: 18 19)
   configure: Could not find a valid Boot JDK. OpenJDK distributions are available at http://jdk.java.net/.
   configure: This might be fixed by explicitly setting --with-boot-jdk
   configure: error: Cannot continue
   configure exiting with result code 1

   很明显的提示了前置的JDK版本不对，因为之前安装的是JDK11，要求18或19。由于我直接从GitHub上拉的最新仓库的源码版本为JDK19的，所以需要替换为JDK12的版本。从仓库的Tags找到JDK12的源码，下载解压后，进入该解压目录从新执行

   bash configure --enable-debug --with-jvm-variants=server

   缺少一些依赖库，报错，按照提示一个个安装，再重新跑一次配置命令即可

   #configure: error: Could not find all X11 headers (shape.h Xrender.h Xrander.h XTest.h Intrinsic.h). You might be able to fix this by running 'sudo apt-get install libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev'.
   #configure exiting with result code 1
   sudo apt-get install libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev
   #configure: error: Could not find fontconfig! You might be able to fix this by running 'sudo apt-get install libfontconfig1-dev'. 
   #configure exiting with result code 1
   sudo apt-get install libfontconfig1-dev
   #configure: error: Could not find alsa! You might be able to fix this by running 'sudo apt-get install libasound2-dev'.
   #configure exiting with result code 1
   sudo apt-get install libasound2-dev

   输出成功后输出：

   ====================================================
   A new configuration has been successfully created in
   /home/k/Downloads/jdk-jdk-12-27/build/linux-x86_64-server-fastdebug
   using configure arguments '--enable-debug --with-jvm-variants=server'.
   
   Configuration summary:
   * Debug level:    fastdebug
   * HS debug level: fastdebug
   * JVM variants:   server
   * JVM features:   server: 'aot cds cmsgc compiler1 compiler2 epsilongc g1gc graal jfr jni-check jvmci jvmti management nmt parallelgc serialgc services shenandoahgc vm-structs zgc' 
   * OpenJDK target: OS: linux, CPU architecture: x86, address length: 64
   * Version string: 12-internal+0-adhoc.k.jdk-jdk-12-27 (12-internal)
   
   Tools summary:
   * Boot JDK:       openjdk version "11.0.14.1" 2022-02-08 OpenJDK Runtime Environment (build 11.0.14.1+1-Ubuntu-0ubuntu1.18.04) OpenJDK 64-Bit Server VM (build 11.0.14.1+1-Ubuntu-0ubuntu1.18.04, mixed mode, sharing)  (at /usr/lib/jvm/java-11-openjdk-amd64)
   * Toolchain:      gcc (GNU Compiler Collection)
   * C Compiler:     Version 7.5.0 (at /usr/bin/gcc)
   * C++ Compiler:   Version 7.5.0 (at /usr/bin/g++)
   
   Build performance summary:
   * Cores to use:   3
   * Memory limit:   3919 MB

   在configure命令以及后面的make命令的执行过程中，会在“build/配置名称”目录下产生如下目录结
   构。不常使用C/C++的读者要特别注意，如果多次编译，或者目录结构成功产生后又再次修改了配
   置，必须先使用“make clean”和“make dist-clean”命令清理目录，才能确保新的配置生效。编译产生的目
   录结构以及用途如下所示：

3. make images

   前排提示，执行该命令之前分配多点内存和核心数（虚拟机下的话）

   make images

   等待…

   出错：内存不足(分配了4G)，由于是虚拟机，swap的空间也挺小1.4G。

   OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00000000ae800000, 547356672, 0) failed; error='Not enough space' (errno=12)
   #
   # There is insufficient memory for the Java Runtime Environment to continue.
   # Native memory allocation (mmap) failed to map 547356672 bytes for committing reserved memory.
   # An error report file with more information is saved as:
   # /home/k/Downloads/jdk-jdk-12-27/make/gensrc/hs_err_pid76398.log

   可以使用命令查看内存和swap大小

   free -m

   我给虚拟机分配了8G内存，重新编译得出如下：

   Stopping sjavac server
   Finished building target 'images' in configuration 'linux-x86_64-server-fastdebug'

   进入提示的路径./build/linux-x86_64-server-fastdebug/jdk/bin，执行version命令

   ./java -version

   输出

   openjdk version "12-internal" 2019-03-19
   OpenJDK Runtime Environment (fastdebug build 12-internal+0-adhoc.k.jdk-jdk-12-27)
   OpenJDK 64-Bit Server VM (fastdebug build 12-internal+0-adhoc.k.jdk-jdk-12-27, mixed mode)

   编译完成。