[R-pkg-devel] CRAN 'blackswan' server configuration

[Tyler]

Hi all,

I have several packages (libopenexr/libimath/libdeflate) that use
CMake on the CRAN that have recently been taken down for failing to
compile on the extratest “blackswan” server. As part of the configure
script, these packages pull the compiler `CC` and `CXX` variables to
build a static library. The failure is occurring because the
“blackswan” server is apparently using ccache in some sort of
non-standard way: grepping the output of `R CMD config CC` in my
configure script to detect ccache does not work, which leads me to
believe there may be an custom alias set up on the server for invoking
a compiler cache tool. You can see the failure logs here:

https://www.stats.ox.ac.uk/pub/bdr/donttest/libdeflate.log

And my configure script here :

https://github.com/tylermorganwall/libdeflate/blob/main/tools/config/configure.R

Note that I've excluded the possibility of whitespace being the issue
as CC is pulling `/usr/bin/ccache` and not an empty string. The only
remaining reason for the failure I can think of is a custom alias. I
have a workaround written and ready to be deployed if that’s indeed
the case, but I don’t want to attempt a fix without confirming the
root cause.

Can someone with access to the blackswan server please provide the
Makeconf configuration file or at the very least, clarify how ccache
is invoked?

Best regards,
Tyler Morgan-Wall