Re: Still seeing Failed assertion: "p[i] == 0" on armv7 buildworld

bob prohaska <fbsd@www.zefox.net> writes:

> All the assertion failures I've seen have been in the clang libraries during
> buildworld. They appear to happen in a variety of cases, indicated by the 
> different .sh and .cpp filenames found in the files under
> http://www.zefox.net/~fbsd/assertion_failure/

Do you have the stdout and stderr of the build somewhere in there as
well?  The make(1) invocation in the readme file shows its output being
redirected to a file.

The assert you mentioned in the subject of your e-mail message, which I
also saw in the readme file, could come from jemalloc.  See these lines
of code for the context

https://github.com/facebook/jemalloc/blob/dev/src/extent.c#L805-L814

That assertion will be tripped when jemalloc sees non-zero memory that
it expects to be zeroed.  See for example

https://github.com/facebook/jemalloc/blob/dev/src/pages.c#L55-L106

Looking at the code, my hypothesis would be that jemalloc thinks it's
committing memory for the first time but the memory is coming back with
non-zero data.

Just curious, but is over-commit enabled on your system?  Here is the
signal jemalloc is using to check

https://github.com/facebook/jemalloc/blob/dev/src/pages.c#L729-L737

> The failures are random in the sense that restarting buildworld either
> produces a new assertion failure in a different library or completion.
>
> It isn't obvious how to capture a stack trace, if you can provide guidance
> I'll give it a try. As is, buildworld simply stops, the machine does not
> crash.

It might be captured for you already?  I noticed files with names
containing "symbolizer-input" and "symbolizer-ouput" like this one

http://www.zefox.net/~fbsd/assertion_failure/hostname_pelorus.zefox.org/symbolizer-output-7282d9

and the output files contain a stack trace like this

  llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
  /usr/src/contrib/llvm-project/llvm/lib/Support/Unix/Signals.inc:731:7

  llvm::sys::RunSignalHandlers()
  /usr/src/contrib/llvm-project/llvm/lib/Support/Signals.cpp:0:5

  SignalHandler
  /usr/src/contrib/llvm-project/llvm/lib/Support/Unix/Signals.inc:0:3

  handle_signal
  /usr/src/lib/libthr/thread/thr_sig.c:0:3

Any idea who or what is creating those files and when?