求助：程序原可正常运行现报x86_64架构未定义符号错误

Hey there, sorry to hear your old project's throwing this linker error now—those undefined symbol issues can be such a headache, especially when it used to work perfectly back in 2017! Let's break down targeted fixes that go beyond just quick tweaks to Build Settings or Build Phases:

• Check for outdated or incompatible libraries/frameworks
  2017 was a long time in Apple ecosystem terms—many older frameworks (like legacy UIWebKit components) or third-party libraries have been deprecated or stopped supporting x86_64. For static libraries, verify they include x86_64 support by running this Terminal command:
  lipo -info /path/to/your/library.a
  If the output doesn't list x86_64, you'll need to get an updated version of the library or rebuild it for modern architectures.

• Deep-dive into Build Settings details
  Even if you've adjusted these before, double-check:

  • Architectures: Ensure x86_64 is explicitly included (some old projects might have it restricted to older arm architectures).
  • Library Search Paths: Broken absolute paths from 2017 (if you moved the project) can prevent the linker from finding libraries. Switch to relative paths where possible.
  • Other Linker Flags: Flags like -all_load or -ObjC might conflict with updated libraries. Try removing non-essential flags temporarily to test.

• Audit Build Phases thoroughly

  • In Link Binary With Libraries, confirm no required frameworks/libraries are marked red (broken references). Re-add any missing ones if needed.
  • Check Compile Sources: Accidentally removing a .m/.swift file from the target is easy to miss—make sure all your project's source files are still listed here.
  • For mixed Objective-C/Swift projects: Verify the Objective-C Bridging Header path is correct and all necessary headers are imported (Xcode's updates can sometimes reset this).

• Wipe old build artifacts
  Legacy build data from 2017 might be conflicting with modern builds:

  1. Go to Product > Clean Build Folder (hold the Option key to reveal this option).
  2. Delete Derived Data: Open Xcode > Settings > Locations > Derived Data, click the arrow to open the folder, and delete all its contents.

• Pinpoint the missing symbol
  The truncated error message doesn't show the exact symbol that's missing—this is your biggest clue! Look at the full error output to see if it's a class (like _OBJC_CLASS_$_LegacyClass), function, or method. This will tell you if a component was renamed, removed, or isn't being linked properly.

If you can share the full error message (with the specific missing symbol) and details about any third-party libraries your project uses, that'll help narrow down the fix even faster!

内容的提问来源于stack exchange，提问作者Shuo Zhao