酿造更新后GCC停止工作

Question

I don't know if this is the right place to ask so let me know if I'm doing anything wrong.

I'm learning c programming, and I was trying to setup git since I want to learn that too. I followed some instructions and git seems to be working fine, but now I get an error whenever I type some gcc command.

I'm new to the whole terminal thing and tried some commands I found on stackoverflow but that didn't resolve my issue.

I get the following message after trying to compile a C programm:

dyld: Library not loaded: /usr/local/lib/libmpfr.4.dylib Referenced 
from: /usr/local/libexec/gcc/x86_64-apple-darwin15.0.0/6.1.0/cc1 
Reason: image not found
gcc: internal compiler error: Abort trap: 6 (program cc1)

I also get the following output after running 'brew doctor':

Warning: You have unlinked kegs in your Cellar Leaving kegs unlinked 
can lead to build-trouble and cause brews that depend on those kegs to 
fail to run properly once built. Run brew link on these: gawk

Warning: Homebrew's sbin was not found in your PATH but you have 
installed formulae that put executables in /usr/local/sbin. Consider 
setting the PATH for example like so echo 'export 
PATH="/usr/local/sbin:$PATH"' >> ~/.bash_profile

gcc was also part of the unlinked kegs which I linked with 'brew link gcc', which at first gave some error message but after running a command from SE this worked.

If I run 'gcc --version' I get the usual output (gcc version 6.1.0).

Any help would be appreciated since I'm eager to continue programming and this is kinda destroying my evening of calm coding :(

Thanks.

EDIT: after restoring backup, $brew update $brew upgrade:

==> Pouring gcc-7.3.0_1.high_sierra.bottle.tar.gz
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink bin/gfortran
Target /usr/local/bin/gfortran
already exists. You may want to remove it:
  rm '/usr/local/bin/gfortran'

To force the link and overwrite all conflicting files:
  brew link --overwrite gcc

To list all files that would be deleted:
  brew link --overwrite --dry-run gcc

Possible conflicting files are:
/usr/local/bin/gfortran

Answer 1

First, have you previously installed gcc from a source other than Homebrew? Second, is your homebrew repo up to date ( brew update )?

If you are on Mac with Command Line Tools installed, running gcc --version exactly as written should return the Apple gcc version supplied with Xcode which is 4.2.1. To prevent conflicts, homebrew links its gcc to gcc-x where x is the current major release. This is why I wonder if your homebrew repo is out of date since the current homebrew gcc version is 7 (eg, gcc-7 --version ).

If you have previously installed a non-homebrew gcc, you could have symlinks pointing to that installation which may return gcc version 6.1.0. If this is the case, your best bet is to remove the non-homebrew gcc version 6.1.0 using the appropriate uninstall methods available from wherever you got it. Now there should be no conflicting gfortran symlinks in /usr/local/bin and reinstalling homebrew gcc from an updated repository should proceed without errors.

If you've never installed a non-homebrew gcc then it should be safe to do as the error instructions indicate with respect to removing the old symlink. This is because /usr/local directory is reserved for the User and would not have any gfortran symlinks unless you put them there via homebrew or some other user installation (which was addressed above).

You also may want to examine brew prune -h which might address some of your issues as well.