whenever I get xcode crashing at launch when it first opens a project, i find the .xcodeproj for that project, but use a terminal.
.xcodeproj is actually a folder (directory) when viewed from the cmd line
then cd into the *.xcodeproj dir and find 2 files:
xcuserdata and project.xcworkspace
rename these to something else. i usually just add a .1 to the end of them
dont mess w/ project.pbxproj file, that is the Real project
then relaunch xcode and pick the project. all windows that you had open will be closed.
project will be in a 'fresh' state but all files will be there. some settings if you had set any of them may be reset also, such as in Schemes.
it seems to be mainly schemes and run-time /debug-time settings that get reset.
I dont know what else gets reset, but usually this gets me back to square 1 and then i can recover.
i found this a long time ago on some forum. it is a brutal problem. a lot of people were suggesting [make a new xcode project
and copy all your files into it, starting from fresh]. that is an even worse solution i think.
those xcuserdata and *.xcworkspace get regenerated when xcode launches and you open the project
the reason to rename instead of delete those files: in case anything you Really need is in them, you can poke in the files to see what's in them that you need.
this falls into the category of Xcode lore I think, not official apple policy, but it has done the trick for me dozens of times. probably >> 100.
i sometimes do this when xcode gets laggy also. it seems to clear a bunch of temp garbage and gets you a responsive dev environment again.