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wankdanker / node-odbc

ODBC bindings for node
MIT License
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Fixed memory leak in ODBC::GetParametersFromArray #8

Closed Xylem closed 10 years ago

Xylem commented 10 years ago

The bug occurs when a query is being executed with usage of parameters array where array is empty. Something along the lines of 

connection.query('SELECT 1;', [], function (err, result) { ... });

In such cases, ODBC::GetParametersFromArray is being executed and since values->Length() is equal to 0, the call to malloc effectively becomes malloc(0). Behavior of such call is not strictly defined. C99 standard states that either a null pointer should be returned or the call should behave as if the requested size was nonzero and a unique pointer is returned with the exception that the address should not be accessed (PDF Warning - ISO/IEC 9899:TC2, section 7.20.3, page 313).

As it stands, glibc displays the latter behavior, additionally defining a minimum allocated size.

The actual cause of the leak is the fact that in all instances where the parameter array returned by ODBC::GetParametersFromArray is freed, it is only done under condition that there were more than 0 parameters in the query - example.

Given enough time and enough queries, those several lost bytes did pile up.

wankdanker commented 10 years ago

Awesome find. Thank you for your work. Released v0.6.10 to npm.

Cheers!