Yes, the old gfortran ~4.8.6 binary can cause this issue. Unfortunately, there
isn't an uninstaller. I wrote up some guidelines for removing it here:
https://thecoatlessprofessor.com/programming/cpp/removing-the-old-r-custom-gfortran-4.8.2-binary/
The gist is:
# Download installer into working
I found the problem. /usr/local/lib had old copies of libgfortran* and
libquadmath* from 2015, and removing these allowed things to proceed.
The current copies are in /usr/local/gfortran/lib.
That directory contains a lot of old junk; I'll probably find more needs
to go too.
Duncan Murdoch
After updating to Catalina, I've installed the Xcode command line tools
version 11.4.1, and gfortran 8.2. When trying to build R, configure dies:
checking whether gfortran appends underscores to external names... yes
checking whether gfortran appends extra underscores to external
names... no
