XCode 4 had a lot of changes over 3.x. Some seemed kinda okay, others seemed horrible. When it came out I did… absolutely nothing, for as long as possible and held on to the 3.x version as long as it was possible to do so.
Since I had to switch to the iTunes-ized Xcode 4, I’ve been using it only as a compiler/debugger, doing all my text editing in emacs on my linux box, using synergy to swap to my mac to compile. I want my editor to be on the same box as as the source code files in case something weird with the network or filesharing service happens. So the project I compile on my mac is served by smb on my linux box. This may sound needlessly complex, but I like having two boxes even after trying dual-screen mac. Also, I had already set up smb to my liking before trying it out, and I already was playing with this even while xcode 3 was current.
With XCode 4, I noticed something weird happening when I made multiple saves in a short duration, e.g. two quick saves in under a minute. The saved changes wouldn’t go into the build for whatever reason. I remember a similar bug with XCode 3, but if you just waited a second and recompiled, it would be okay. But with XCode 4, sometimes the new changes would never get propogated across the network and compiled even after waiting for a long time. I eventually realized if I saved the file on my linux box again by making a small edit, XCode would pick it up and compile it, but oddly enough, only if the save happened a minute or so after the first.
However, after inspecting the fileshared source code on my mac with other editors, it was clear that this wasn’t a filesharing issue, but simply XCode caching the file. The “Touch command” that existed in XCode 3 would presumably fix this (although I would be afraid to use it if caching is the suspect), but it was inexplicably removed with XCode 4.
When the caching is an issue, you get a warning that looks like ‘null character(s) ignored’ or an error that says ‘missing @end’ and sometimes the file will be cut in half in XCode.
After dealing with this for over a year I just found out you can prevent these by making sure you have no source files open in XCode. It seems the editor uses it’s own cache, and the compiler goes directly to compiling the cache instead of the disk. Note that if you click on an error in the left side panel, this opens up the editor. So now I just create a new tab with a .png file and close all other xcode tabs. When googling this issue over the last year I saw no mentions of this bug, so maybe no one else uses XCode networked. Noting here just in case.