lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

On 01/17/2015 04:15 AM, Sean Conner wrote:
It was thus said that the Great Andrew Starks once stated:
If you always error, you can
pretend that errors never happen, until you can't. In a garbage
collected language, the places where you need to clean the state up
are pretty limited, so this may be more true of Lua than of C, or
   But you can still leak resources if you don't clear your references.  I
just found such a bug at work at one place, and now I'm afraid of all the
paths I neglected to clean up references leading up to that point.

Indeed, I recently ran into a bug in which a database transaction was 'leaked', i.e. a transaction was started, an error raised in the code between the start and commit, and it was pcall-caught higher up the call stack, without rolling back the transaction. The higher-level code then continued using the database connection with the pending partial transaction (and subsequent updates to the DB) never getting committed until the process terminated and the subsequent updates were rolled back.

In C++ this kind of thing often can be conveniently avoided by using the Resource Acquisition Is Initialization paradigm, or if not, less conveniently with try-catch blocks. In Lua, I find it a bit of a PITA to try to release resources using xpcall. But frankly I prefer it to "return nil,msg".