Add documentation about fixing crashes when upgrading to Xcode 7

[gfontenot]

Creating a project with liftoff and then opening it in Xcode 7 beta 6 is resulting in a crash, for some reason. I'm unclear on if this is our fault (I don't feel like it should be), but maybe we're doing something slightly wrong?

[MrAlek]

Might be CocoaPods. I've never had a CocoaPods project work in Xcode 7 beta 6.

[gfontenot]

I'd bet that it's actually something with our shared dependency: Xcodeproj. Using the --no-cocoapods flag still results in a crash for me.

[gfontenot]

fwiw, this was an "issue" with the Xcode 6 betas as well, and it worked itself out. My hope is that the same will happen here. Projects open fine in Xcode 6 right now.

[marcelofabri]

Is this the exception you're getting?

ASSERTION FAILURE in /Library/Caches/com.apple.xbs/Sources/IDEXcode3ProjectSupport/IDEXcode3ProjectSupport-8181.3/Xcode3Core/LegacyProjects/Frameworks/DevToolsCore/DevToolsCore/TargetSnapshots/XCBuildFileRefDGSnapshot.m:474
Details:  Cannot call addBuildFileRef: when file refs are frozen
Object:   <XCBuildFileRefArrayDGSnapshot: 0x7f88ffbb7190>
Method:   -addBuildFileRef:
Thread:   <NSThread: 0x7f89004053a0>{number = 16, name = (null)}
Hints:   None
Backtrace:
  0  0x0000000110737574 -[IDEAssertionHandler handleFailureInMethod:object:fileName:lineNumber:assertionSignature:messageFormat:arguments:] (in IDEKit)
  1  0x000000010f2ff08a _DVTAssertionHandler (in DVTFoundation)
  2  0x000000010f2ff2a1 _DVTAssertionFailureHandler (in DVTFoundation)
  3  0x0000000117b610b4 -[XCBuildFileRefArrayDGSnapshot addBuildFileRef:] (in DevToolsCore)
  4  0x0000000117b3dadf -[XCBuildPhaseDGSnapshot(DependencyGraphCreation) groupDependencyNode:ifNecessaryForLaterProcessingWithMacroExpansionScope:] (in DevToolsCore)
  5  0x0000000117b51ce4 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) _processOutputNodes:forRegionVariantName:processedPaths:originalBuildRule:withMacroExpansionScope:] (in DevToolsCore)
  6  0x0000000117b504e7 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) _computeDependenciesForBuildFileReference:usingBuildRule:withMacroExpansionScope:processedPaths:] (in DevToolsCore)
  7  0x0000000117b5299e -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForBuildFileReference:usingBuildRule:withMacroExpansionScope:] (in DevToolsCore)
  8  0x0000000117b52e4b -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForBuildFileReference:withMacroExpansionScope:] (in DevToolsCore)
  9  0x0000000117b3e514 -[XCBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForAllBuildFileReferencesWithMacroExpansionScope:] (in DevToolsCore)
 10  0x0000000117b55a2f -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForAllBuildFileReferencesWithMacroExpansionScope:] (in DevToolsCore)
 11  0x0000000117b56e15 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesWithMacroExpansionScope:] (in DevToolsCore)
 12  0x0000000117a8d535 -[XCProductTypeSpecification computeDependenciesWithMacroExpansionScope:] (in DevToolsCore)
 13  0x0000000117b36e80 -[XCNativeTargetDGSnapshot(DependencyGraphCreation) computeDependenciesWithMacroExpansionScope:] (in DevToolsCore)
 14  0x0000000117a0a2d5 -[PBXTargetBuildContext createDependencyGraphWithTargetDGSnapshot:] (in DevToolsCore)
 15  0x0000000117a264f7 -[PBXTargetBuildContext(DependencyGraphEvents) dg_setTargetSnapshot:] (in DevToolsCore)
 16  0x0000000117a25bbc -[PBXTargetBuildContext(DependencyGraphEvents) processDependencyGraphEvents] (in DevToolsCore)
 17  0x0000000117a851c2 -[XCBlockQueue _processNextBlockInThreadSlotNumber:] (in DevToolsCore)
 18  0x0000000117a85444 -[XCBlockQueue _processBlocksInThreadSlotNumber:] (in DevToolsCore)
 19  0x00007fff924c5084 __NSThread__start__ (in Foundation)
 20  0x00007fff9657a9b1 _pthread_body (in libsystem_pthread.dylib)
 21  0x00007fff9657a92e _pthread_body (in libsystem_pthread.dylib)
 22  0x00007fff96578385 thread_start (in libsystem_pthread.dylib)

[gfontenot]

That's it exactly

[marcelofabri]

I've opened a radar about this. Let's hope it'll be fixed.

BTW, I don't think it's CocoaPods fault, as I was able to open another project using CP on Xcode 7b6.

[ghost]

I'm getting the same error in my project since Xcode 7b3, I'm not using CocoaPods.

[marcelofabri]

They closed my radar as a duplicate:

Duplicate of 22424448 (Open)

Let's hope tomorrow's GM fix this!

[gfontenot]

Looks like this is still happening in Xcode 7 GM.

I have no idea where to go from here.

[ghost]

Yep, still crashes.

[gfontenot]

In theory, if we can figure out what's going wrong (and how to fix it), we should be able to add a liftoff repair command. Unfortunately, I don't totally know what's wrong and don't really know where to start debugging. The crash log would imply that we (or more specifically, xcodeproj) are freezing some file refs that Xcode expects to be mutable, but I have no idea how that would be indicated in the XML or what we can do to fix it.

[gfontenot]

interestingly enough the crash does not happen in the 7.1 beta.

this is fun.

[ghost]

Good news, thanks.

[marcelofabri]

I'm seeing the same thing here, but I'm also clueless.

[mattrubin]

After experimenting with a new, empty liftoff-generated project:
It has something to do with Main.storyboard and the "Compile Sources" build phase. Remove the storyboard from the build phase and Xcode 7b6 has no trouble opening the project. Re-add the storyboard to the list of files to compile and Xcode crashes almost immediately.

It seems that Xcode is trying to pre-compile or somehow cache the storyboard, and Xcode 7b6 can't handle the storyboard for some reason.

[marcelofabri]

@mattrubin Nice discovery! I've tested this and also worked.

Luckily, there's a pending PR (#238) to fix this. It's probably not hard to create a liftoff repair command.

[gfontenot]

A clue!

So now the question is: is it worth it to create a repair command, especially since this seems to be fixed in 7.1 and we have a (trivial) reproducible workaround?

[jakecraige]

@mattrubin @marcelofabri @gfontenot That PR is now MERGED.

[priteshshah1983]

Are there instructions on how to do a local bleeding-edge build? I'd love to try this fix.

[gfontenot]

so this is already fixed in master, what isn't fixed is providing some kind of repair command to remove and re-add the storyboard (or I guess all storyboards?). I'm still not 100% sure this is something we want to do. Maybe we can write a standalone script to do this?

[priteshshah1983]

Pardon my ignorance, but I wanted to build the binary myself by cloning the master branch. I was hoping you could point me to that.

[gfontenot]

There's no binary, it's just a ruby script. If you pull down master, you can run it through the bin/liftoff script

[jakecraige]

I'm definitely learning more towards either a script to do it or simply writing down how to resolve this. It's a very one off thing so adding a whole new command to handle it for this one time seems a bit much.

[gfontenot]

Agreed. I'm changing the title of this issue to reflect the actionable item.