1-过五关斩六将开发属于自己的jdk版本

1.1 简介

这里主要做一下笔记,如果比较感兴趣也可以直接查阅官网open jdk building

OpenJDK是JDK的开放源码版本,了解源码学习更优秀的编程思想。

1.2 克隆代码

git clone https://git.openjdk.java.net/jdk/

切换分支到jdk-11+28

git checkout jdk-11+28

1.3 运行配置：

bash configure

如果configure由于缺少依赖项（工具链、构建工具、外部库或引导JDK）而失败，大多数情况下，它会打印一份关于如何在平台上解决这种情况的建议。按照说明操作，然后再次尝试运行bash configure。

运行成功后会有如下日志打印
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1.4 运行Make

make images

这个版本会有BUG如下错误所示:

在这里插入图片描述

issue 链接

上面图片有点小我们继续看

1.4.1 问题1:

/src/hotspot/share/runtime/arguments.cpp:1461:35: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
      if (old_java_vendor_url_bug != DEFAULT_VENDOR_URL_BUG) {
                                  ^  ~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

修复方法:
打开文件arguments.cpp:1461 修改1461行代码为如下所示:

if (strcmp(old_java_vendor_url_bug , DEFAULT_VENDOR_URL_BUG)!=0) {

1.4.2 问题2

=== Output from failing command(s) repeated here ===
* For target hotspot_variant-server_libjvm_objs_sharedRuntime.o:
/Users/song/Desktop/Computer/A/github/jdk/src/hotspot/share/runtime/sharedRuntime.cpp:2798:85: error: expression does not compute the number of elements in this array; element type is 'double', not 'relocInfo' [-Werror,-Wsizeof-array-div]
      buffer.insts()->initialize_shared_locs((relocInfo*)locs_buf, sizeof(locs_buf) / sizeof(relocInfo));
                                                                          ~~~~~~~~  ^
/Users/song/Desktop/Computer/A/github/jdk/src/hotspot/share/runtime/sharedRuntime.cpp:2797:14: note: array 'locs_buf' declared here
      double locs_buf[20];
             ^
/Users/song/Desktop/Computer/A/github/jdk/src/hotspot/share/runtime/sharedRuntime.cpp:2798:85: note: place parentheses around the 'sizeof(relocInfo)' expression to silence this warning
      buffer.insts()->initialize_shared_locs((relocInfo*)locs_buf, sizeof(locs_buf) / sizeof(relocInfo));
                                                                                    ^
1 error generated.

* All command lines available in /Users/song/Desktop/Computer/A/github/jdk/build/macosx-x86_64-normal-server-release/make-support/failure-logs.
=== End of repeated output ===

No indication of failed target found.
Hint: Try searching the build log for '] Error'.

修复方法:
打开2798行修改代码为这个

buffer.insts()->initialize_shared_locs((relocInfo*)locs_buf,(sizeof(locs_buf)) /(sizeof(relocInfo)));

1.4.3 问题三:

src/java.desktop/macosx/native/libawt_lwawt/awt/CSystemColors.m:134:9: error: converting the result of '?:' with integer constants to a boolean always evaluates to 'true' [-Werror,-Wtautological-constant-compare]
    if (colorIndex < (useAppleColor) ? sun_lwawt_macosx_LWCToolkit_NUM_APPLE_COLORS : java_awt_SystemColor_NUM_COLORS) {
        ^
1 error generated.

同理，参考github【https://github.com/openjdk/jdk/commit/4622a18a】修改源码。

打开134行修改代码为

if (colorIndex < ((useAppleColor) ? sun_lwawt_macosx_LWCToolkit_NUM_APPLE_COLORS :
    java_awt_SystemColor_NUM_COLORS)) {

1.4.5 问题四:

ERROR: Build failed for target 'default (exploded-image)' in configuration 'macosx-x86_64-normal-server-release' (exit code 2)
Stopping sjavac server

=== Output from failing command(s) repeated here ===
* For target support_native_java.desktop_libjsound_PLATFORM_API_MacOSX_MidiUtils.o:
/Users/coachhe/Tools/jdk-compile/openjdk11/src/java.desktop/macosx/native/libjsound/PLATFORM_API_MacOSX_MidiUtils.c:263:31: error: cast to smaller integer type 'MIDIClientRef' (aka 'unsigned int') from 'void *' [-Werror,-Wvoid-pointer-to-int-cast]
static MIDIClientRef client = (MIDIClientRef) NULL;
                              ^~~~~~~~~~~~~~~~~~~~
/Users/coachhe/Tools/jdk-compile/openjdk11/src/java.desktop/macosx/native/libjsound/PLATFORM_API_MacOSX_MidiUtils.c:264:29: error: cast to smaller integer type 'MIDIPortRef' (aka 'unsigned int') from 'void *' [-Werror,-Wvoid-pointer-to-int-cast]
static MIDIPortRef inPort = (MIDIPortRef) NULL;
                            ^~~~~~~~~~~~~~~~~~
/Users/coachhe/Tools/jdk-compile/openjdk11/src/java.desktop/macosx/native/libjsound/PLATFORM_API_MacOSX_MidiUtils.c:265:30: error: cast to smaller integer type 'MIDIPortRef' (aka 'unsigned int') from 'void *' [-Werror,-Wvoid-pointer-to-int-cast]
static MIDIPortRef outPort = (MIDIPortRef) NULL;
                             ^~~~~~~~~~~~~~~~~~
/Users/coachhe/Tools/jdk-compile/openjdk11/src/java.desktop/macosx/native/libjsound/PLATFORM_API_MacOSX_MidiUtils.c:471:32: error: cast to smaller integer type 'MIDIEndpointRef' (aka 'unsigned int') from 'void *' [-Werror,-Wvoid-pointer-to-int-cast]
    MIDIEndpointRef endpoint = (MIDIEndpointRef) NULL;
                               ^~~~~~~~~~~~~~~~~~~~~~
   ... (rest of output omitted)

* All command lines available in /Users/coachhe/Tools/jdk-compile/openjdk11/build/macosx-x86_64-normal-server-release/make-support/failure-logs.
=== End of repeated output ===

No indication of failed target found.
Hint: Try searching the build log for '] Error'.
Hint: See doc/building.html#troubleshooting for assistance.

make[1]: *** [main] Error 2
make: *** [default] Error 2

修复方式:
src/java.desktop/macosx/native/libjsound/PLATFORM_API_MacOSX_MidiUtils.c文件的4个地方。但是修改方式是统一的，都是将括号里的内容（MIDIClientRef,MIDIPortRef,MIDIEndpointRef）修改为unsigned long。

修改前：

263 static MIDIClientRef client = (MIDIClientRef) NULL;
264 static MIDIPortRef inPort = (MIDIPortRef) NULL;
265 static MIDIPortRef outPort = (MIDIPortRef) NULL;

471 MIDIEndpointRef endpoint = (MIDIEndpointRef) NULL;

修改后：

263 static MIDIClientRef client = (unsigned long) NULL;
264 static MIDIPortRef inPort = (unsigned long) NULL;
265 static MIDIPortRef outPort = (unsigned long) NULL;

471 MIDIEndpointRef endpoint = (unsigned long) NULL;

重新执行make即可看到编译成功如下图所示:
在这里插入图片描述

1.5 验证新构建的JDK：

./build/*/images/jdk/bin/java -version

如下图所示:
在这里插入图片描述
打开如下目录即可看到JDK信息,可以尝试配置此jdk为默认JDK使用

不过每个小伙伴电脑环境可能不太一样,遇到的问题也不一定完全相同,静下心来多搜搜或者研究下这个C代码的语法错误即可,Open JDK底层有些版本确实不够严谨, 不过社区都有对应解决方案。

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JDK11源码1, Java1