[swift-dev] Reduce app startup time by combining swift-libs

[Alex Blewitt]

> On 17 Feb 2017, at 21:58, Michel Loenngren via swift-dev <swift-dev at swift.org> wrote:
> 
> All,
> 
> When starting an app that includes swift these libs are being loaded:
> 
> libswiftCoreGraphics.dylib 
> libswiftDispatch.dylib     
> libswiftObjectiveC.dylib
> libswiftCore.dylib
> libswiftDarwin.dylib
> libswiftFoundation.dylib
> 
> which adds considerable delay to our app startup time (compared to running a pure objective-c codebase). Is anybody aware of a way to reduce startup by combining these libs into a single lib for faster load time?

At the moment, these are provided as individual libraries because they are built as separate libraries on the command line. It's possible to build a static version of the core library with swiftc -static-stdlib on Darwin (there are still work in progress items for Linux and Foundation).

https://bugs.swift.org/browse/SR-730 <https://bugs.swift.org/browse/SR-730>

However, note that the majority of the libraries that you list are also used in a pure objective-c codebase; for example, running otool -L on Mail.app gives:

	/System/Library/Frameworks/CoreGraphics.framework/Versions/A/CoreGraphics
	/usr/lib/libobjc.A.dylib
	/usr/lib/libSystem.B.dylib
	/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation
	/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation

(Dispatch is embedded in libSystem on Darwin)

So the libraries you load are the same ones (in effect) to the ones used by your Objective-C application, in all likelihood. The difference is probably in the way that the libraries are set up and the dispatch once code is executed - which are necessary steps in bringing the Swift runtime up for your application.

Alex

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