`as.integer64.character()` should check `errno` at the C level

[DavisVaughan]

In the case of strings that represent values that are out of the range of representable values by a long long, strtoll() will return LLONG_MAX or LLONG_MIN and set errno to ERANGE.

bit64::as.integer64("12312312423432842390482390482348328992382930482093842384092842834238904823908423904230423908924300")
#> integer64
#> [1] 9223372036854775807

See the Return Value section of:
http://www.cplusplus.com/reference/cstdlib/strtoll/

I imagine that after calling strtoll() here you could check errno, and return NA if it is set to ERANGE (possibly with a warning), which seems like it might be better behavior for R
https://github.com/truecluster/bit64/blob/e428535bc31982d85bc3f4faa1f2ae8481280781/src/integer64.c#L205

[MichaelChirico]

We are also affected by this -- a side effect is that c.integer64 can cause precision loss, e.g.

c(bit64::as.integer64(1L), "18446744073709551615")
# integer64
# [1] 1                   9223372036854775807

(this from trying to coerce uint64 values to int64)

[MichaelChirico]

@DavisVaughan would you like to have a go at a PR? :)

[MichaelChirico]

re my own comment, I also filed #44.