RFR: 8138916: Logging write function does not allow for long enough messages (original) (raw)

Dmitry Samersoff dmitry.samersoff at oracle.com
Tue Oct 27 11:52:07 UTC 2015

Rachel,

In worst case (windows, overflow) the code would parse format string four times. Also NEW_C_HEAP_ARRAY takes a lock and might become a performance bottleneck.

POSIX equivalent of _vscprintf(fmt, args) is vsnprintf(NULL, 0, fmt, args)

So it might be better to create os::log_vcprintf(fmt, args), then write code at log.hpp as:

int buf_len = os::log_vcprintf(fmt, args); assert(buf_len < 2*page_size, "Stack overflow in logging"); char buf[buf_len]; vsprintf(buf, fmt, args);

-Dmitry

On 2015-10-26 23:58, Rachel Protacio wrote:

Hello, all,

Please review this fix to the faulty write function from the Unified Logging framework. Summary: In logging/log.hpp, the logging vwrite function previously asserted that the buffer remains within 512 characters, which is too short for logging message of non-pre-determined length, e.g. for vtable and itable function names. Now, the function resizes the buffer to the appropriate length, asserting only that the resulting buffer is valid. Includes tag "logtest" to test that logging can print an output of 518 characters. Open webrev: http://cr.openjdk.java.net/~rprotacio/8138916/ Bug: https://bugs.openjdk.java.net/browse/JDK-8138916 Includes own acceptance test, and passes JPRT and remote hotspot/test tests. Thank you, Rachel

-- Dmitry Samersoff Oracle Java development team, Saint Petersburg, Russia

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