unable to execute command: Segmentation fault: 11 swift frontend command failed due to signal (use -v to see invocation)

Here's how I was able to find out what the problem was:

1. Click on the issue in the issue navigator (⌘ + 4, then click on the line with the red ! at the start)
2. At the bottom of the file that appears, there should be a line that says something like:

1. While emitting IR SIL function @_TToZFC4Down8Resource12getInstancesfMS0_U__FTSS6paramsGVSs10DictionarySSPSs9AnyObject__9onSuccessGSqFGSaQ__T__7onErrorGSqFT5errorCSo7NSError8responseGSqCSo17NSHTTPURLResponse__T___T_ for 'getInstances' at /path/to/file.swift:112:5

3. The location where your error occurred is at the end of that line. (In this case, on line 112 of file.swift in getInstances).

I was trying to add the PayPal framework to my iOS Project (Xcode 7.2 and Objective C language). When building it did not throw any error, but when I tried to archive the Project and make the IPA, I was getting that error

unable to execute command: Segmentation fault: 11

Screenshot:

After struggling for a long time, I disabled the Bitcode in Project's Target > Build Settings > Enable Bitcode. Now the project can be archived. Please check the following screenshot.

Can't really give a straight solution on this (although I'm sure it's an Apple bug), but I just came across the exact same error message and happen to solve it. Here's what I did:

In General

1. Comment out recently changed Swift code (check commits) until the app compiles again
2. Command-click each called method in the failing line and check if there could be an ambiguity

My Example

In my case (I was using the XMPPFramework written in Objective-C) the failing code looked like this:

for roomMessage: XMPPRoomMessage in self.messages {    let slices = split(roomMessage.nickname(), { $0 == "_" }, allowEmptySlices: false)}

Once I replaced roomMessage.nickname() with "0_test" the code didn't fail any more. So I command-clicked the method nickname() (twice) and here's what I saw:

My guess was that the Swift 1.1 compiler has problems with figuring out which method to call if the exact type of an object is not clear. So I made the type of roomMessage explicit and got another error which I fixed by removing the braces behind the nickname() method call. This made my app build again. Here's the working code:

for roomMessage: XMPPRoomMessageCoreDataStorageObject in self.messages {    let slices = split(roomMessage.nickname, { $0 == "_" }, allowEmptySlices: false)}

I hope this helps someone out there to investigate the issue more quickly than I did.