RFR(XS): 8056930: Output host info under some condition for core dump

[Yumin Qi]

Calvin,

   Thanks for the review, yes, it is webrev01 (now updated with buffer 
len to 1024, see below).

/lpBuffer/[out]

    A pointer to a buffer that receives the computer name or the cluster
    virtual server name.

    The length of the name may be greater than MAX_COMPUTERNAME_LENGTH
    characters because DNS allows longer names. To ensure that this
    buffer is large enough, set this parameter to*NULL*and use the
    required buffer size returned in the/lpnSize/parameter.

/lpnSize/[in, out]

    On input, specifies the size of the buffer, in*TCHARs*. On output,
    receives the number of*TCHARs*copied to the destination buffer, not
    including the terminating*null*character.

    If the buffer is too small, the function fails and*GetLastError*
    <http://msdn.microsoft.com/en-us/library/windows/desktop/ms679360%28v=vs.85%29.aspx>returns
    ERROR_MORE_DATA. This parameter receives the size of the buffer
    required, including the terminating*null*character.

    If/lpBuffer/is*NULL*, this parameter must be zero.

In winbase.h:

#ifndef _MAC
#define MAX_COMPUTERNAME_LENGTH 15
#else
#define MAX_COMPUTERNAME_LENGTH 31
#endif


So it is 15 in most case, but it is not enough for most cases in network 
name, I put 4K here think that is enough for most of the cases.
According to the description, I set buffer = NULL, and size to 0, the 
call failed.

I updated again, and set the buffer len as 1K, 1024 bytes, which I think 
should be enough.
The specs in MSDN are confusing some time and not consistent in their 
pages.

Thanks
Yumin




On 9/8/2014 10:29 AM, Calvin Cheung wrote:
> Yumin,
>
> os_windows.cpp
>
> 1592   char buffer[4096];
>
> Why do you need a 4k buffer?
>
> According to: 
> http://msdn.microsoft.com/en-us/library/windows/desktop/ms724220(v=vs.85).aspx
> "Each name can be up to 255 bytes total. "
>
> So maybe 256 is sufficient?
>
> btw, is your new webrev located at: 
> http://cr.openjdk.java.net/~minqi/8056930/webrev01/ ?
>
> thanks,
> Calvin
>
> On 9/8/2014 10:17 AM, Yumin Qi wrote:
>> Hi,
>>
>>   I made a small change to Windows part, when GetComputerNameEx 
>> fails, instead of do nothing, output "N/A".
>>
>> Thanks
>> Yumin
>>
>> On 9/5/2014 2:46 PM, Yumin Qi wrote:
>>> Please review
>>>
>>> Bug:  https://bugs.openjdk.java.net/browse/JDK-8056930
>>> Webrev:  http://cr.openjdk.java.net/~minqi/8056930/webrev00
>>>
>>>   After java crashed, we would like to know the host on which it 
>>> failed especially when doing parallel testing on multiple machines. 
>>> The most useful for knowing host name is telling if the test is 
>>> hardware related, that the test can only repeat on it. This piece of 
>>> code help to print out host name in debug mode.
>>>
>>>   Test: manually tested on Unix/Linux/Windows with 
>>> -XX:+CrashGCForDumpingJavaThread.
>>>    JPRT
>>>
>>> Thanks
>>> Yumin
>>
>