Category Archives: Programming

Xperf Basics: Recording a Trace (the ultimate easy way)

This post can be found through https://tinyurl.com/etwtracing, and an alternate version of these instructions can be found here. If your Windows computer is running slowly – if a program takes a long time to launch, if a game has a … Continue reading

Posted in Performance, Programming, uiforetw, xperf | Tagged , , | 35 Comments

Graph All the Things (Using WPT 10)

Event Tracing for Windows (ETW) has always recorded a rich set of data and allowed graphing it all on the same timeline. With the creation of UIforETW (which records more data) and the new* ETW trace viewer (which can graph … Continue reading

Posted in Performance, Programming, xperf | Tagged , , , , , , | 15 Comments

Programming is Puzzles

When I’m describing what I do for a living to non-programmers I sometimes say that I solve puzzles. I solve fascinating puzzles that are different every day, and there’s no answer key, and very often nobody else knows the solution. … Continue reading

Posted in Investigative Reporting, Performance, Programming, Visual Studio | Tagged , , , | 11 Comments

Profiling the profiler: working around a six minute xperf hang

Anytime my computer is a little bit slow I’m likely to record a trace and take a quick look. If I’m lucky I’ll find an easy workaround, in which case I’ve got a potential blog post and a smoother running … Continue reading

Posted in Investigative Reporting, Performance, Programming, xperf | Tagged , | 13 Comments

ETW Trace Compression (and xperf syntax refresher)

Despite extolling the virtues of wprui for recording ETW traces (here, and here) I’ve actually returned to using xperf.exe in batch files to do most of my trace recording. It gives me more precise control over what is recorded, and … Continue reading

Posted in Performance, Programming, xperf | Tagged , | 17 Comments

Intel Underestimates Error Bounds by 1.3 quintillion

Intel’s manuals for their x86/x64 processor clearly state that the fsin instruction (calculating the trigonometric sine) has a maximum error, in round-to-nearest mode, of one unit in the last place. This is not true. It’s not even close. The worst-case … Continue reading

Posted in Floating Point, Investigative Reporting, Programming | Tagged , , | 131 Comments

A Crash of Great Opportunity

It was a fairly straightforward bug. A wide-character string function was called with a byte count instead of a character count, leading to a buffer overrun. After finding the problem the fix was as simple as changing sizeof to _countof. … Continue reading

Posted in Code analysis, Code Reliability, Programming | Tagged | 11 Comments

Please Calculate This Circle’s Circumference

“Please write a C++ function that takes a circle’s diameter as a float and returns the circumference as a float.” It sounds like the sort of question you might get in the first week of a C++ programming class. And … Continue reading

Posted in Floating Point, Programming | Tagged , , , | 75 Comments

Undefined Behavior *Can* Format Your Drive

My last post mentioned the ‘standard’ risks of undefined behavior such as having your hard drive formatted or having nethack launched. I even added my own alliterative risk – singing sea shanties in Spanish. The list of consequences bothered some … Continue reading

Posted in Programming, Security | Tagged | 16 Comments

Buggy Security Guidance from Apple

In February 2014 Apple published their Secure Coding Guide. I glanced through it and noticed that their sample code for detecting integer overflow was buggy – it triggered undefined behavior, could be optimized away, and was thus unsafe to use. … Continue reading

Posted in Programming, Security | Tagged | 40 Comments