mac下出现xcrun error导致gcc无法使用的解决办法

Have you upgraded to OS X El Capitan from App Store ?

Have you suddenly started getting the following error in your project?

xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

If yes, then here is the solution

xcode-select --install