Should you’ve ever thought or heard one thing like this, within the title, it is virtually actually not true.
MQL applications are compiled by native MetaEditor’s instruments and executed inside MetaTrader beneath its full management. By design, MQL program doesn’t and shouldn’t include any means to interrupt the terminal.
The one exception for the rule is the case when MQL code imports a DLL. DLL is a binary program which is exterior the management of the terminal, and therefore is ready to produce demolicious results not solely to the terminal however to Home windows typically. This is the reason MetaTrader prevents DLL imports by default, and a person should allow them explicitly on per single occasion foundation, solely at his/her discretion and danger. Should you confronted an issue with the terminal, which you assume comes from an MQL program, verify if it makes use of a DLL within the first place.
Most of publicly obtainable MQL applications and all MQL applications delivered by way of MQL market don’t use DLLs.
If DLL shouldn’t be concerned, MQL program by itself shouldn’t be a motive of MetaTrader crash. Nonetheless, if it is occurred, it is almost definitely an induced error within the terminal, compelled by excessive load or different circumstances encountered whereas executing authentic MQL directions and built-in MQL APIs.
The nice analogue for the terminal and MQL program operating in it’s a browser exhibiting a webpage (these days a webpage makes use of a bunch of applied sciences – JavaScript, graphics, multimedia, networking, databases and so forth – just about as it’s in MQL program). Most likely you noticed moments when your browser crashes on particular web page. Did you blame the web page or the browser? Even when we admit that some pages could also be written incorrectly or in a malicious method, the browser is chargeable for dealing with this reliably. Errors should be intercepted and reported.
MetaTrader is a money-handling software program, so it is speculated to be rock stable, and particularly to lure any errors which can creep into MQL code. Particularly bearing in mind that many authors of MQL applications are merchants, not builders, and their errors are forgivable.
A division by zero or an try of accessing a component out of array’s certain are examples of most typical errors that happen in MQL supply codes. Invalid pointer entry or operating out of stack reminiscence are much less frequent, but additionally unrecoverable runtime errors for a single MQL program written with out precautions.
All such circumstances are intercepted by MetaTrader and reported to the Specialists log. The MQL program with the error is stopped and unloaded, however the terminal retains operating.
But most of errors should not thought-about essential and don’t result in MQL program termination. For instance, math perform name on an invalid argument (e.g. sq. root of a adverse quantity) or working with invalid deal with for a file or an indicator belong to this sort of errors, to call a number of. After such errors MQL program will most likely produce incorrect outcomes, and require person’s intervention anyway, however that is one other story.
Bear in mind: there are not any applications with out flaws. Relating to MQL program, it is regular to have errors inside, however they need to not have an effect on the terminal.
The one unhealthy factor with the terminal, that may be attributable to native MQL program, is an infinite loop. If it occurs in an skilled adviser, a script, or a service, it hundreds a single core of your CPU (till you cease it). If it occurs in an indicator, it hangs a part of MetaTrader’s GUI. The final case is certainly harmful, nevertheless it’s not a crash, strictly talking. Such hangs are attainable as a result of indicators are executed within the GUI thread of MetaTrader. Personally, I take into account this a flaw within the terminal’s design, as a result of it breaks the precept of “sandboxing”, utilized to MQL in lots of different elements (restricted entry to information, community, different MQL applications, and so forth). As a platform, MetaTrader ought to stop any harm from MQL program being executed. Most likely this might be mounted sometime by MQ crew.
So what to do if MetaTrader went down unexpectedly? Attempt to gather all logs from the terminal folder and crashlogs (for MT5 it is in /Customers/<username>/AppData/Roaming/MetaQuotes/Crashes) and supply for MQ on the boards. Attempt to reproduce the issue with minimal configuration (single chart, solely associated MQL applications), and describe particulars on the best way to reproduce it. Strive completely different MT builds and environments as a workaround to alleviate the issue earlier than it is pinned down and stuck.
