Why are backtraces (sometimes) useless

Why are backtraces (sometimes) useless

[Yaron Minsky]

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I've had a lot of experience lately with OCaml backtraces sucking, and I'm 
not sure what's going on. We're working on a decent-sizes project (about 
10-kloc) that uses threads and a decent amount of functorization. One thing 
we've noticed is that backtraces are almost completely useless --- generally 
speaking, they have lots of "Called from unknown location" messages, and 
almost no useful data. They often skip over functions on the call stack of 
the error in surprising ways.

I guess the question is this: what kind of situations cause backtraces to 
drop information in the ways described above?

Also, is there anyone out there actively using the native-code backtrace 
patches that people have come up with? I'm curious to hear other people's 
experiences.

y

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Re: [Caml-list] Why are backtraces (sometimes) useless

[malc]

On Fri, 24 Jun 2005, Yaron Minsky wrote:

> I've had a lot of experience lately with OCaml backtraces sucking, and I'm
> not sure what's going on. We're working on a decent-sizes project (about
> 10-kloc) that uses threads and a decent amount of functorization. One thing
> we've noticed is that backtraces are almost completely useless --- generally
> speaking, they have lots of "Called from unknown location" messages, and
> almost no useful data. They often skip over functions on the call stack of
> the error in surprising ways.
>
> I guess the question is this: what kind of situations cause backtraces to
> drop information in the ways described above?
>
> Also, is there anyone out there actively using the native-code backtrace
> patches that people have come up with? I'm curious to hear other people's
> experiences.

Native code backtracing i did is constrained by the fact that only
functions that contain gc call site are included into backtrace.
I even included an example which showcases this limitation.

-- 
mailto:malc@pulsesoft.com

Re: [Caml-list] Why are backtraces (sometimes) useless

[Richard Jones]

On Fri, Jun 24, 2005 at 12:39:24PM -0400, Yaron Minsky wrote:
> Also, is there anyone out there actively using the native-code backtrace 
> patches that people have come up with? I'm curious to hear other people's 
> experiences.

I've actually been doing backtraces with gdb in native code.  Works
reasonably well provided your program is going through a lot of C
code.

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
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