Alexandre,
AFAICS, this code actually causes infinite recursion, and here's why:
1. formals grabs returns the formals of the function identified by
sys.function(sys.parent()) this ends up being print.new, whose first
argument is x
2. mget looks for the symbol x in envir = as.environment(-1L) which ends
up being the evaluation frame for print.new [1]
3. x in that environment resolves the the object you are trying to print
4. print() is called on that object, and dispatches to print.new() ...
[1]
> debug(mget)
> foo
*<snip>*
[1] "envir" "ifnotfound" "inherits" "mode" "x"
Browse[2]> *envir*
*<environment: 0x7fa39bf1b278>*
Browse[2]> sys.frames()
[[1]]
<environment: 0x7fa39bf1b550>
*[[2]]*
*<environment: 0x7fa39bf1b278>*
*<snip>*
Browse[2]> sys.calls()
[[1]]
function (x, ...)
UseMethod("print")(x)
*[[2]]*
*print.new(x)*
*<snip>*
Browse[2]> class(envir$x)
[1] *"new"*
Hope that helps.
~G
On Mon, Sep 5, 2016 at 4:48 PM, Alexandre Courtiol <
alexandre.court...@gmail.com> wrote:
> Hi all, not sure if you will call this a bug or something else but the
> following silly call trigger a low level error:
>
> foo <- list(x=1)
> class(foo) <- "new"
> print.new <- function(x, ...) print(mget(names(formals())))
> foo
>
> > Error: C stack usage 7969412 is too close to the limit
>
>
>
> --
> Alexandre Courtiol
>
> http://sites.google.com/site/alexandrecourtiol/home
>
> *"Science is the belief in the ignorance of experts"*, R. Feynman
>
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>
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>
--
Gabriel Becker, PhD
Associate Scientist (Bioinformatics)
Genentech Research
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