"cannot run mixed C/Fortran code"
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 checking whether mixed C/Fortran code can be run... configure: WARNING: cannot run mixed C/Fortran code configure: error: Maybe check LDFLAGS for paths to Fortran libraries? I don't have LDFLAGS set. I'm not certain I'm running the right compilers (I might have old ones that have precedence on the path). Are these the versions I should be seeing? $ clang --version Apple clang version 11.0.3 (clang-1103.0.32.59) Target: x86_64-apple-darwin19.6.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin $ gfortran --version GNU Fortran (GCC) 8.2.0 Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. If those are the right versions, any other suggestions on how to fix the configure problem? Duncan Murdoch