-Xpkginfo：总是参数导致javac 1.7.0_25崩溃

Question

我的目标

我们需要将-Xpkginfo:always参数传递给javac编译器。我们正在使用javac 1.7.0_25。说-Xpkginfo，此版本可用java doc。

1. 预期结果：应生成package-info.class个文件
2. 实际结果：javac编译器崩溃：

An exception has occurred in the compiler (1.7.0_25). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.

java.lang.NullPointerException
        at com.sun.tools.javac.comp.Enter.visitTopLevel(Enter.java:291)
        at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:459)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.complete(Enter.java:484)
        at com.sun.tools.javac.comp.Enter.main(Enter.java:469)
        at com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:929)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:824)
        at com.sun.tools.javac.main.Main.compile(Main.java:439)
        at com.sun.tools.javac.main.Main.compile(Main.java:353)
        at com.sun.tools.javac.main.Main.compile(Main.java:342)
        at com.sun.tools.javac.main.Main.compile(Main.java:333)
        at com.sun.tools.javac.Main.compile(Main.java:76)
        at com.sun.tools.javac.Main.main(Main.java:61)

到目前为止我尝试过的

它与Java 1.8兼容，但是很遗憾，由于我们仍然有旧的Java代码，因此我们无法升级Java编译器。

编辑

使用javac -X来确保1.7.0_25具有-Xpkginfo自变量。答案是肯定的：

PS C:\SVN\products\faa_mx\vs2017.install2> javac -X
  -Xlint                     Enable recommended warnings
  -Xlint:{all,cast,classfile,deprecation,dep-ann,divzero,empty,fallthrough,finally,options,overrides,path,processing,rawtypes,serial,static,try,unchecked,varargs,-cast,-classfile,-deprecation,-dep-ann,-divzero,-empty,-fallthrough,-finally,-options,-overrides,-path,-processing,-rawtypes,-serial,-static,-try,-unchecked,-varargs,none} Enable or disable specific warnings
  -Xbootclasspath/p:<path>   Prepend to the bootstrap class path
  -Xbootclasspath/a:<path>   Append to the bootstrap class path
  -Xbootclasspath:<path>     Override location of bootstrap class files
  -Djava.ext.dirs=<dirs>     Override location of installed extensions
  -Djava.endorsed.dirs=<dirs> Override location of endorsed standards path
  -Xmaxerrs <number>         Set the maximum number of errors to print
  -Xmaxwarns <number>        Set the maximum number of warnings to print
  -Xstdout <filename>        Redirect standard output
  -Xprint                    Print out a textual representation of specified types
  -XprintRounds              Print information about rounds of annotation processing
  -XprintProcessorInfo       Print information about which annotations a processor is asked to process
  -Xprefer:{source,newer}    Specify which file to read when both a source file and class file are found for an implicitly compiled class
  -Xpkginfo:{always,legacy,nonempty} Specify handling of package-info files

[也尝试使用1.7.0_80，相同的崩溃：An exception has occurred in the compiler (1.7.0_80).

java.lang.NullPointerException
        at com.sun.tools.javac.comp.Enter.visitTopLevel(Enter.java:291)
        at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:459)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.complete(Enter.java:484)
        at com.sun.tools.javac.comp.Enter.main(Enter.java:469)
        at com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:929)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:824)
        at com.sun.tools.javac.main.Main.compile(Main.java:439)
        at com.sun.tools.javac.main.Main.compile(Main.java:353)
        at com.sun.tools.javac.main.Main.compile(Main.java:342)
        at com.sun.tools.javac.main.Main.compile(Main.java:333)
        at com.sun.tools.javac.Main.compile(Main.java:76)
        at com.sun.tools.javac.Main.main(Main.java:61)

替代解决方案

使用javac 1.8和使用命令行javac -source 1.7 -target 1.7 MyClass.java有意义吗？

Answer 1

在Java 1.7中，如果将-Xpkginfo:always传递给javac，则它仅接受package-info.java空文件。如果您传递非空文件，则会发生崩溃。

使用1.8，javac可以在一个命令行中处理空文件和非空文件。

因此，1.7的解决方法是多次调用javac，一次调用所有空的package-info.java文件，另一次调用非空文件。