Reimplement signal handler to avoid async-unsafe functions

[zzxuanyuan]

@bbockelm @pcanal This patch copies the code of signal handling in CMSSW. It avoids async-unsafe functions in signal handler functions.

For reference, see the link https://github.com/bbockelm/cmssw/blob/stacktrace_handler_revisit/FWCore/Services/src/InitRootHandlers.cc

I tried this patch with some simple multi-thread test cases and it worked fine. Is there any complicated test cases I can run? I think this patch is not very ready to merge, but it achieved basic functions. Any criticisms are welcome.

[bbockelm]

Don't need a forward dec'l if you already include

[FonsRademakers]

And please use ROOT coding standards.

[bbockelm]

(by the way, is there a good online ref for these to link to?)

[pcanal]

Yes, of course :), at https://root.cern.ch/coding-conventions

[bbockelm]

Thanks Philippe - Zhe, can you run through this guide and try to get the code to compliance?

@pcanal - when contributing to CVMFS, they provide an automated tool (based on cpplint). I see you reference astyle for managing whitespace. Do you have anything similarly automated you use?

[bbockelm]

Hi Zhe,

You may also want to pull in the work done here:

cms-sw/cmssw#11662

Specifically,
a) Allow the read function to timeout.
b) Avoid use of execv on Linux. CERN uses LD_PRELOAD tricks to insert a custom version of this function into the executable. Unlike the POSIX documentation, the version of execv at CERN is not async signal safe.

Brian

[zzxuanyuan]

@bbockelm Sure. I will polish up my code.

[zzxuanyuan]

Hi Philippe,

@pcanal Could you take a look at this new patch? Is there any test cases I can run with?

Thanks!

[pcanal]

since written is not used outside the loop, it ought to be declared inside.

[pcanal]

Is there any test cases I can run with?

Not specifically. Some of the code would be exercised by calling ::Fatal( ... )

[pcanal]

Hi,

What was the result of your testing? Did you create a test we can add to roottest?
Did you already update to follow the coding conventions? (I do not see an newer version so I commented on what I see)

Thanks,
Philippe.

[pcanal]

Class not part of the public interface need to either be defined in an unnamed namepace in the source file or within the ROOT::Internal namespace or as protected/private subclass of the using class.