llvm dev - Aug 2016 - LLVM libraries and custom assertions.

Is there a simple method for compiling a custom assertion header/call into all
the LLVM libraries? I want my application to be able to handle any thrown
assertions (ie; as an exception) and recover or crash gracefully. I already have
a custom header in place in the application's source, however this
doesn't have an effect on [most of] the already compiled lib's.
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You can consider catching SIGABRT, or maybe LD_PRELOAD'ing an
implementation for abort (not sure if the latter is possible, but
should be easy to try out).  I don't know how to do better than that
without recompiling LLVM.

Another option is to let LLVM's client register an "error handler"
that gets called instead of abort() on a failed assert, but you'll
have to change and rebuild LLVM to do this (and have a non-standard
assert definition).  This can be a little cleaner, depending on what
you're trying to do.  I don't have a good sense of what others think
of this, but I'll be for upstreaming a mechanism of this sort to LLVM.

-- Sanjoy

On Mon, Aug 15, 2016 at 4:19 PM, Paul Hancock via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Is there a simple method for compiling a custom assertion header/call into
> all the LLVM libraries? I want my application to be able to handle any
> thrown assertions (ie; as an exception) and recover or crash gracefully. I
> already have a custom header in place in the application's source,
however
> this doesn't have an effect on [most of] the already compiled
lib's.
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>


-- 
Sanjoy Das
http://playingwithpointers.com

Catching the error and using your own handler should be no problem. There is
stuff like install_fatal_error_handler() and the CrashRecoveryContext.

However llvm today isn't really designed/tested for recovery after an error,
so your milage may vary.

- Matthias
> On Aug 15, 2016, at 4:27 PM, Sanjoy Das via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> You can consider catching SIGABRT, or maybe LD_PRELOAD'ing an
> implementation for abort (not sure if the latter is possible, but
> should be easy to try out).  I don't know how to do better than that
> without recompiling LLVM.
> 
> Another option is to let LLVM's client register an "error
handler"
> that gets called instead of abort() on a failed assert, but you'll
> have to change and rebuild LLVM to do this (and have a non-standard
> assert definition).  This can be a little cleaner, depending on what
> you're trying to do.  I don't have a good sense of what others
think
> of this, but I'll be for upstreaming a mechanism of this sort to LLVM.
> 
> -- Sanjoy
> 
> On Mon, Aug 15, 2016 at 4:19 PM, Paul Hancock via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Is there a simple method for compiling a custom assertion header/call
into
>> all the LLVM libraries? I want my application to be able to handle any
>> thrown assertions (ie; as an exception) and recover or crash
gracefully. I
>> already have a custom header in place in the application's source,
however
>> this doesn't have an effect on [most of] the already compiled
lib's.
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> 
> 
> 
> 
> -- 
> Sanjoy Das
> http://playingwithpointers.com
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Catching SIGABRT seems reasonable for a graceful crash, but I'm also already
making use of LLVM's internal fatal_error_handler. However said handler is
only called for very specific things, the rest all use direct calls to assert,
do I need to disable the LLVM_ENABLE_ASSERTIONS flag to change this?

I also just noticed however that there's an exception handler flag too,
which I didn't notice before as it's called "LLVM_ENABLE_EH".
Will be rebuilding now with that enabled and will see if it works how I want it
to, but I have to question the sensibility of naming the flag like that when
there's already flags with much longer names...?


- Paul

________________________________
From: Sanjoy Das <sanjoy at playingwithpointers.com>
Sent: 16 August 2016 09:27
To: Paul Hancock
Cc: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] LLVM libraries and custom assertions.

You can consider catching SIGABRT, or maybe LD_PRELOAD'ing an
implementation for abort (not sure if the latter is possible, but
should be easy to try out).  I don't know how to do better than that
without recompiling LLVM.

Another option is to let LLVM's client register an "error handler"
that gets called instead of abort() on a failed assert, but you'll
have to change and rebuild LLVM to do this (and have a non-standard
assert definition).  This can be a little cleaner, depending on what
you're trying to do.  I don't have a good sense of what others think
of this, but I'll be for upstreaming a mechanism of this sort to LLVM.

-- Sanjoy

On Mon, Aug 15, 2016 at 4:19 PM, Paul Hancock via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Is there a simple method for compiling a custom assertion header/call into
> all the LLVM libraries? I want my application to be able to handle any
> thrown assertions (ie; as an exception) and recover or crash gracefully. I
> already have a custom header in place in the application's source,
however
> this doesn't have an effect on [most of] the already compiled
lib's.
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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>


--
Sanjoy Das
http://playingwithpointers.com
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