RFR[9u-dev]: 8151442: jstack doesn't close quotation marks properly with threads' name greater than 1996 characters

[Dmitry Samersoff]

Cheleswer,

Fix (as immediate solution) looks good for me.

But IMHO, silent truncation of the output inside output stream is not a
correct behavior. So please file a follow-up CR to have it addressed.

-Dmitry

On 2016-03-18 10:54, Cheleswer Sahu wrote:
> Hi,
> 
>  
> 
> Please review the code changes for https://bugs.openjdk.java.net/browse/JDK-8151442.
> 
>  
> 
> Webrev Link: http://cr.openjdk.java.net/~csahu/8151442/
> 
>  
> 
> Bug Brief: 
> 
> In jstack thread dumps , thread name greater than 1996 characters doesn't close quotation marks properly. 
> 
>  
> 
> Problem Identified:
> 
> Jstack is using below code to print thread name
> 
>  
> 
> src/share/vm/runtime/thread.cpp
> 
> void JavaThread::print_on(outputStream *st) const {
> 
>   st->print("\"%s\" ", get_thread_name());
> 
>  
> 
> Here "st->print()"  internally uses max buffer length as O_BUFLEN (2000).
> 
>  
> 
> void outputStream::do_vsnprintf_and_write_with_automatic_buffer(const char* format, va_list ap, bool add_cr) {
>   char buffer[O_BUFLEN];
> 
>  
> 
>  
> 
> do_vsnprintf_and_write_with_automatic_buffer() finally calls  "vsnprintf()"  which truncates the anything greater than the max size(2000). In this case thread's name(> 1996) along with quotation marks (2) 
> 
> plus one terminating character exceeds the  max buffer size (2000), therefore the closing quotation  marks gets truncated.
> 
>  
> 
>  
> 
> Solution:
> 
> Split the  "st->print("\"%s\" ", get_thread_name())" in two statements
> 
> 1.       st->print("\"%s", get_thread_name());
> 
> 2.       st->print("\" ");
> 
>  
> 
> This will ensure presence of closing quotation mark always.
> 
>  
> 
>  
> 
> Regards,
> 
> Cheleswer
> 
>  
> 
>  
> 
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> 


-- 
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.