Where is Xcode's build folder?

Before Xcode 4 the build used to be created in the root folder of my project. I can no longer find it.

Where can i find the build folder?

Where is derived data located?

DerivedData is a folder located in ~/Library/Developer/Xcode/DerivedData by default. It's the location where Xcode stores all kinds of intermediate build results, generated indexes, etc. DerivedData location can be configured in Xcode preferences (Locations tab). So now and then you run into odd build problems.

What is Project_dir?

PROJECT_DIR. Identifies the directory containing the project ( .xcodeproj ) $(PROJECT_DIR)/build is used as the create the default value for: Intermediate Build Files Path OBJROOT.

~/Library/Developer/Xcode/DerivedData is now the default.
You can set the prefs in Xcode to allow projects to specify their build directories.