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

[Cheleswer Sahu]

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