Over the years of working on TheDarkMod game, we have amassed 1K lines of natvis code, 95 type definitions in total. Natvis has become an inherent part of good debugging experience, but it is available only on Windows. This story is about my attempt to extend this experience to the Linux side.

This multipart article explains how to reimplement most of the inherent natvis features on top of GDB pretty printers, provides a declarative approach to pretty printers similar to how natvis works, gives a solid deep-printing implementation similar to that of MSVC, and discusses the major issues of GDB value inspection system.

read more

It is well-known that Debug build in Visual C++ is very slow compared to Release build, with the typical ratio about 10-20 times. Various reasons behind it are often stated, and some people even believe that it is inevitable because it is caused by lack of compiler optimizations.

If some issue happens only on a large dataset or in a real-time application, and it cannot be extracted into a smaller test case, then developer is forced to debug Release build. Which is rather painful experience, because debugger has problems showing control flow, values of local variables, sometimes even currently executed function, since all these concepts are messed up by optimizations. Ironically, the more optimizer-friendly your code is, the worse would be your experience of debugging Release build =)

Luckily, Visual C++ provides a lot of settings for tuning speed-vs-comfort ratio. It is entirely possible to create a "Fast Debug" configuration which works only a few times slower than Release yet is pretty easy to debug due to lack of optimizations.

read more

Some time ago I wrote a surprising answer to stackoverflow question "Fastest way to get IPv4 address from string". At that very moment I discovered that _mm_shuffle_epi8 instruction combined with sufficiently large lookup-table can do wonders. Actually, this exact methodology was used to implement vectorized merging algorithm in one of my previous blog posts.

Inspired by the new discovery, I tried to apply this LUT + shuffle idea to some well-known and moderately generic problem. I tried to apply the idea to accelerate conversion from UTF-8 to UTF-16 and was successful. Initially, I had to postpone all efforts on the problem due to PhD-related activities. After that I thought that I would write a scientific article on the topic. When it became clear that I don't want to lose time on anything like that anymore, I decided to write about it in a blog. As a result, almost three years after the initial work (update: it is four years already), I finally managed to write this report, describing the algorithm and the utf8lut library.

read more