I am working with fortran on my MAC. Everything was working, but when I started to use brew to install for example python or other programs, everything started to crash, because I think several files has been moved from their original positions and probably some libraries were mixed. I read on Internet how to solve my errors, but I was unable to do that. I will post below the error I find, when I launch gfortran
dyld: Library not loaded: /usr/local/opt/isl/lib/libisl.23.dylib
Referenced from: /usr/local/Cellar/gcc/10.2.0_2/libexec/gcc/x86_64-apple-darwin17/10.2.0/f951
Reason: image not found
gfortran: internal compiler error: Abort trap: 6 signal terminated program f951
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://github.com/Homebrew/homebrew-core/issues> for instructions.
I solved my problem. Normally on MAC when you try to install other programs, like python, ipython, or others, it can happen that your program like gfortran (connected with gcc) cannot work anymore, giving an error message as the one specified by me above. This tells you that the libraries of gfortran have been not found. Premising that I am not expert of programming, I would suggest to solve similar issues by typing first brew doctor, which permits you to see which kinds of error are present. In my case it was spotted that the link to the gfortran library was not connected. So I have done brew unlink, brew instal gcc and then brew link. This entails that the missing link is again stabilized. I suggest also to have a look at Homebrew GitHub forum (https://github.com/Homebrew/homebrew-core/issues), which can give more targeted answers