GCC 4.8 To Improve Diagnostics Abilities

In a battle against LLVM/Clang, GCC 4.8 will improve the code diagnostics support to better assist developers in debugging code errors/warnings in a user-friendly manner.

One of the long-advertised features of LLVM's Clang C/Objective-C/C++ compiler has been that it offers more user-friendly diagnostics than the GNU Compiler Collection. Historically this has been true, especially against GCC 4.2 -- the last GPLv2 compiler release. However, GCC developers have been working to improve this situation. With GCC 4.8, it looks like more of this work will come to fruition.

On the LLVM web-site there's long been the Clang Expressive Diagnostics page to show off that Clang's error reporting/diagnostics are superior to GCC. "In addition to being fast and functional, we aim to make Clang extremely user friendly. As far as a command-line compiler goes, this basically boils down to making the diagnostics (error and warning messages) generated by the compiler be as useful as possible. There are several ways that we do this. This section talks about the experience provided by the command line compiler, contrasting Clang output to GCC 4.2's output in several examples."

Now on the GCC side they have been working on a Clang Diagnostics Comparison Wiki page. This comparison page was brought up yesterday at DebConf Managua when talking about building Debian packages with LLVM/Clang, but those details will be saved for another Phoronix article.

The GCC Clang Diagnostics Comparison is now about showing off where the latest GCC code is ahead of Clang. "It is often repeated that the Clang compiler produces far superior diagnostics to GCC. For example the Expressive Diagnostics page shows examples where Clang's diagnostics were indeed superior to GCC 4.2. However, that version of GCC is a few years old, and GCC has improved considerably since then. This page revisits the examples using recent versions of GCC and add further interesting examples."

Among the advertised features is GCC 4.8 introducing support for printed column numbers, caret diagnostics instead of pretty print expressions, typedef preservation, selective unwrapping, automatic macro expansion, quality of implementation and attention to detail, recursive template instantiations, and C++ template errors. There's also a Red Hat page promoting GCC diagnostics.

While the GCC improvements are nice, it will still be a number of months before GCC 4.8 is officially released. At that point, GCC 4.8 will be competing against LLVM/Clang 3.2 with LLVM/Clang 3.3 likely being mid-way in development.