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Inside Apple's new Xcode 4 development tool

The Fixit feature

Developers report Apple has also introduced a new Fixit feature that provides advanced code completion and flags common bugs or typos using the same red underlining that Mac OS X uses system wide to indicate spelling errors.

The Fixit feature can suggest appropriate symbol spellings and supply correct punctuation, assisting developers to write code faster while making fewer mistakes. A static analysis can find and flag common bugs and errors such as a failure to properly release memory that is no longer needed.

Xcode 4 is also reported to support new version control features for collaborative development, enabling coders to checkout, commit changes and update content in projects stored on Subversion and Git version control systems (which work with multiple versions of files over time, like Time Machine).

New tools also allow users to compare different files for changes over time that have been checked into a version control system and revert or merge code into the latest version.

Xcode 4

Apple shares new LLDB debugger as open source with LLVM

Xcode 4 is also reported to include a significant new version of the modern Low Level Virtual Machine (LLVM) Compiler, which Apple has been supporting as an open source project to eventually replace GNU Compiler Collection (GCC), the tool most Unix-based development systems use to convert source code to executable object code targeted to a specific processor.

LLVM is a modular compiler system designed to create faster, more optimized code. The new LLVM Compiler 2 now supports C++ in addition to the C and Objective C languages, and compiles code up to twice as fast as GCC. The code it creates also runs faster than code compiled with GCC, with Mac OS X code reportedly running up to 25% faster and iOS code running as much as 60% faster, just through improvements made in optimizing the compilation of the same source code.

Also within Xcode 4 is an entirely new debugger system Apple designed for performance and efficiency, resulting in faster finding and fixing of bugs. The new debugger is modeled after LLVM's modular architecture, and is therefore named LLDB. Apple is also said to be releasing its internal LLDB project as open source, and will make it available to third parties alongside the open source LLVM compiler.

Playing new Instruments

Another major feature delivered alongside Xcode 4 will be a new version of Instruments (originally code named Xray), Apple's graphical tool for code performance profiling based on Sun's DTrace technology.

The new Instruments adds new time profiler support for iOS development, and includes new features that help developers examine how their application code interacts with other apps and the system's kernel, in order to find where apps are spending their processing time and allocating their resources in a very complex computing environment.

Instruments is also said to include support for identifying abandoned memory that has been referenced but not actually needed, enabling developers to reduce the memory footprint their apps demand. The tool will also add profiling analysis support for OpenGL ES, an important tool for iOS developers building high performance games and other apps that make use of sophisticated graphics.