.Call improperly formed

[halpo]

from Prof. Brian Ripley:

For a package with a namespace (all these days), .C etc are allowed
without a PACKAGE argument to refer to entry points in the package,
but that was never checked.

I wrote some diagnostic code, and the namespace identification is not
doing a particularly good job. For example calls like

 drop(.C(...))
 do.call(".C", args)

are all missed, including some in your package (and ca 25 others). We
will do better in R-devel, but if you want the package to work well in
earlier versions you should add PACKAGE arguments.

An even better idea is to register your entry points and refer to them
as R objects. This is done extensively in R itself, so for example
fisher.test contains

    else PVAL <- .C(C_fexact, nr, nc, x, nr, as.double(-1), 
        as.double(100), as.double(0), double(1), p = double(1), 
        as.integer(workspace), mult = as.integer(mult), PACKAGE = "stats")$p

(and the PACKAGE = "stats" is not actually needed).