segfault when using a `fastmap` to store data read using `arrow`

[dgkf]

I've been trying to chase down this bug for a while, and although I don't have a solution I've tried my best to pin down a reproducible example in a reprex over in dgkf/reprex-covr-segfault.

In short, a package that uses a pattern such as

function(f) {
  m <- fastmap::fastmap()  
  m$set("data", arrow::read_parquet(f))
}

will segfault when trying to calculate code coverage.

At it's core, it usually segfaults any time a package tries to store a arrow data.frame inside a fastmap stored somewhere within the package namespace.

I say usually because coverage will run to completion on the current CRAN release of covr if there is an if statement (and maybe others?) somewhere in the package code. I was only able to reliably test this by putting an if (TRUE) {} statement in the .onLoad function, but the behavior was rather sporadic and I think it's also affected by the presence/absence of S3 method registration. The development version of CRAN fails regardless.