MacPro（Core 2 Duo）上Xcode 9突然卡顿至无法使用，求助解决

Hey there, let’s break down how to fix this frustrating Xcode slowdown—you’ve already tried some basic tweaks, so we’ll focus on deeper, targeted fixes that often resolve post-update issues on older hardware like your Core 2 Duo Mac Pro.

Step 1: Reset Xcode Preferences #

Automatic updates sometimes mess with Xcode’s preference files, leading to unexpected lag. Here’s how to reset them safely:

• First, quit Xcode completely.
• To back up your current preferences (just in case), copy this file to a safe location: ~/Library/Preferences/com.apple.dt.Xcode.plist
• Open Terminal and run this command to delete corrupted preferences:

  defaults delete com.apple.dt.Xcode
  

• Restart Xcode and see if the slowness improves.

Step 2: Wipe Xcode’s Caches & Derived Data #

Over time (especially after updates), Xcode piles up cached files and derived data that can clog your system. Clearing these is often a quick win:

• Quit Xcode first.
• Clear Derived Data: Go to Xcode > Preferences > Locations, click the small arrow next to the Derived Data path, then delete the entire folder in Finder.
• Clear Xcode Caches: In Finder, navigate to ~/Library/Caches/com.apple.dt.Xcode and delete all contents inside.
• For a faster terminal approach, run these two commands:

  rm -rf ~/Library/Developer/Xcode/DerivedData/*
  rm -rf ~/Library/Caches/com.apple.dt.Xcode/*
  

• Restart Xcode and test performance.

Step 3: Check System Resource Drain #

Your 4GB RAM and Core 2 Duo are on the lower end for Xcode 9, so post-update background processes might be hogging resources:

• Open Activity Monitor (in /Applications/Utilities/):
  • Check the CPU tab: Look for processes using high CPU (especially Xcode-related ones or unexpected background tasks like Spotlight indexing).
  • Check the Memory tab: See if Xcode is using nearly all available RAM (if so, closing other apps might help temporarily).
  • Check the Disk tab: If disk usage is spiking at 100%, Spotlight might be re-indexing your SSD after the restart. To fix this:
    1. Go to System Preferences > Spotlight > Privacy
    2. Add your SSD drive to the list, then remove it immediately—this triggers a fresh reindex. Wait for it to finish before opening Xcode.

Step 4: Verify Xcode’s Integrity #

Sometimes automatic updates corrupt Xcode’s installation files. Let’s check and repair:

• Repair Command Line Tools: Open Terminal and run:

  xcode-select --install
  

  Follow the prompts to reinstall the command line tools, then run:

  xcodebuild -license
  

  Agree to the license if prompted.
• Check Xcode’s Code Signature: Run this in Terminal to verify Xcode’s files are uncorrupted:

  codesign -vvv /Applications/Xcode.app
  

  If you see errors like "invalid signature", you’ll need to re-download Xcode from the App Store (make sure to back up your projects first).

Step 5: Disable Resource-Heavy Xcode Features #

Xcode 9 has some features that can strain older hardware. Try disabling these temporarily:

• Turn Off Live Issues: Go to Xcode > Preferences > General and uncheck "Show live issues".
• Disable Source Control Auto-Refresh: Go to Xcode > Preferences > Source Control and uncheck "Enable Source Control".
• Close any unnecessary tabs in Xcode (like unused project windows or documentation tabs) to reduce memory load.

Step 6: Test in Safe Mode #

Safe Mode disables third-party plugins and startup items, which might be conflicting with Xcode after the update:

• Restart your Mac and hold down the Shift key until you see the Apple logo.
• Once in Safe Mode, open Xcode and test if it’s still slow.
• If it runs smoothly, the issue is likely from a third-party plugin or startup item:
  • Go to System Preferences > Users & Groups > Login Items and remove any non-essential apps from the list.
  • Double-check for leftover Xcode plugins in ~/Library/Application Support/Xcode/Plug-ins—delete any that aren’t critical.
• Restart your Mac normally and test Xcode again.

Step 7: Address Hardware Limitations #

While your SSD helps, 4GB RAM is tight for Xcode 9 on High Sierra. If all else fails:

• Close every other app when using Xcode to free up RAM.
• Check if your Mac Pro supports more RAM (Core 2 Duo models typically max out at 8GB—upgrading could make a noticeable difference).

内容的提问来源于stack exchange，提问作者glez