Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Wed, 18 May 2011 14:21:44 +0200

Hi all,

I got several caGateway crashes with the error message:
"errSymBld callocMustSucceed failed count 256 size 4"
Obviously it has some memory problems.

But is it really a good idea to abort a server only because of (probably

temporary ?) resource problems? I think no. I would even go so far to

say that the whole idea of the *MustSucceed functions is wrong. Many

parts of EPICS are meant to run continuously as servers. Aborting the

program when something goes wrong is probably the worst thing one can

do. Thus I would consider any call of a *MustSucceed function during

run-time a design flaw of the program. (It is probably a different

question if this makes sense during startup.) An error in a lower layer

of software should be passed to higher layers to be handled properly.

That is what almost all systems functions have always done - either by

returning a status code or by throwing an exception. But simply calling

abort does not give the application the slightest chance to do anything.

In this case, it seems the gateway wanted to post an error message

(maybe about being out of memory?). But callocMustSucceed called by

errSymLookup, in turn called by casStrmClient::sendErrWithEpicsStatus

killed the whole application instead. This not only killed even those

parts of the server that were still functioning. Additionally it makes

debugging quite hard.

Therefore I propose to remove all *MustSucceed functions from future

EPICS releases and allow and require proper error handling by the

application.

Any opinions on this topic?

Dirk