RFR(S): 8188122: Path length limits on Windows leads to obscure class loading failures

[Calvin Cheung]

Hi Ioi,

On 10/16/17, 4:15 PM, Ioi Lam wrote:
> Hi Calvin,
>
> From your test case:
>
>   44     private static final int MAX_PATH = 260;
>   ...
>
>   53         int subDirLen = MAX_PATH - classDir.toString().length() - 2;
>   54         if (subDirLen > 0) {
>   55             char[] chars = new char[subDirLen];
>   56             Arrays.fill(chars, 'x');
>   57             String subPath = new String(chars);
>   58             destDir = 
> Paths.get(System.getProperty("test.classes"), subPath);
>   59         }
>   60
>   61         CompilerUtils.compile(sourceDir, destDir);
>
> It looks like at least part of the JDK is able to read and write files 
> that are in paths longer than 260 characters.
>
> For JDK-8188122, it seems the problem exists only with 
> -Xbootclasspath/a is used. Have you tested if you can use -cp to load 
> classes from the long directory?
Yes, the problem exists only with -Xbootclasspath/a because the call 
path is different comparing with -cp.

Call path with -Xbootclasspath/a:
     ClassPathDirEntry::open_stream() at classLoader.cpp:274 0x7ffff5ca48d0
     ClassLoader::load_class() at classLoader.cpp:1,412 0x7ffff5ca94a8
     SystemDictionary::load_instance_class() at 
systemDictionary.cpp:1,524 0x7ffff671e141
     SystemDictionary::resolve_instance_class_or_null() at 
systemDictionary.cpp:847 0x7ffff671bb3f
     SystemDictionary::resolve_or_null() at systemDictionary.cpp:263 
0x7ffff671a1a1
     SystemDictionary::resolve_or_null() at systemDictionary.cpp:268 
0x7ffff671a215
     JVM_FindClassFromBootLoader() at jvm.cpp:777 0x7ffff6204544
     Java_java_lang_ClassLoader_findBootstrapClass() at 0x7ffff4a8a0e6

Call path with -cp:

     ClassFileParser::fill_instance_klass() at classFileParser.cpp:5,309 
0x7ffff5c93a6d
     ClassFileParser::create_instance_klass() at 
classFileParser.cpp:5,289 0x7ffff5c938bd
     KlassFactory::create_from_stream() at klassFactory.cpp:214 
0x7ffff63462ef
     SystemDictionary::resolve_from_stream() at 
systemDictionary.cpp:1,144 0x7ffff671cadd
     jvm_define_class_common() at jvm.cpp:943 0x7ffff6205376
     JVM_DefineClassWithSource() at jvm.cpp:963 0x7ffff620588d
     Java_java_lang_ClassLoader_defineClass1() at 0x7ffff4a89c68

Note that ClassPathDirEntry::open_stream() isn't called when -cp is used.
>
> If that's the case, maybe we should fix -Xbootclasspath/a so that it 
> can handle over 260 chars on Windows?
No easy way of fixing it other than using the unicode version of windows 
API.

thanks,
Calvin
>
> Thanks
>
> - Ioi
>
>
>
> On 10/16/17 3:15 PM, Calvin Cheung wrote:
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8188122
>>
>> Adding a warning message if the full path or the directory length 
>> exceeds MAX_PATH on windows.
>>
>> Example warning messages.
>>
>> 1) The full path exceeds MAX_PATH:
>>
>> Java HotSpot(TM) 64-Bit Server VM warning: construct full path name 
>> failed: total length 270 exceeds max length of 260
>>     dir 
>> T:\\testoutput\\jtreg\\JTwork\\classes\\2\\runtime\\LoadClass\\LongPath.d\\xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
>> length 259
>>     name Hello.class length 11
>>
>> 2) The directory path exceeds MAX_PATH:
>>
>> Java HotSpot(TM) 64-Bit Server VM warning: os::stat failed: path 
>> length 265 exceeds max length 260
>>     path 
>> T:\\testoutput\\jtreg\\JTwork\\classes\\2\\runtime\\LoadClass\\LongPath.d\\xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\\xxxxx
>>
>> webrev:
>>     http://cr.openjdk.java.net/~ccheung/8188122/webrev.00/
>>
>> Testing:
>>     JPRT (including the new test)
>>
>> thanks,
>> Calvin
>