Dr. Dobb's Journal - March 2008 - (Page 26)

Core Technology DETECTING BUGS IN SAFETY-CRITICAL CODE Static Analysis and Systematic Testing Again, safety-critical developers are required to demonstrate coverage. There are of course different kinds of coverage, and the risk the code carries dictates which kind of coverage is required. In the DO-178B Standard for aviation, the riskiest code Coverage Statement (1 case) a 1 b — c — Decision (2 cases) 1 0 1 0 0 0 — 0 — 1 0 0 — 0 — — 1 0 Figure 3: Redundant condition warning from CodeSonar. MCDC (4 cases) Table 1: The number of test cases required for full coverage. requires 100-percent modified condition/ decision coverage (MCDC). The next two most risky classes require 100-percent decision coverage and statement coverage, respectively. The least risky code, such as the inflight entertainment system, has no coverage requirements at all. Most developers are familiar with statement coverage, and anyone who has tried to test with 100-percent statement coverage knows how difficult it is to achieve. Decision coverage is more stringent—it requires that all branches in the control flow are taken. You must make test cases that force all your conditional expressions to evaluate both true and false. MCDC coverage is stronger still, and means that all subexpressions in a conditional should be evaluated to both true and false. Consider what this means in terms of the number of test cases for this code snippet: if (a || b || c) foo(); Figure 4: Fragment of a report from CodeSonar illustrating a redundant condition. I/O Controls x x x x x High-Speed for Real-Time applications Built-In custom Property Editors Automatic and Custom Sizing. No Restrictive Bitmaps Look and Feel of Real Hardware Includes : Switches, Gauges, Sliders, Led’s, Led Bar, Led Spiral, Integer/Binary/Hexadecimal Displays, Tanks, Valves, Motors, LCD Matrix, Spectrum Display, Percent and Pie Graph, Odometers, Analog Clock, Image Display, Rotation Display, and Mode Combo Box. Plot Control x x x x x x x x High-Speed for Real-Time applications Unlimited Number of Channels & Axes Full Customizable External Toolbar Legends, Tables, Limits, Labels, Annotations, Cursors Gradient Backgrounds Log Files and Data Export and Import Save images to BMP, PNG, JPEG, TIF, GIF and EMF Many built in channel types : Tracy, Trace-XY, Bar, Bubble, Fill, Bi-Fill, Digital, Differential and Sweep Interval (EKG) Std Pack .Net x 28 Controls x Basic I/O Controls ActiveX & VCL Also Available Pro Pack .Net x 55 Controls x Basic & Advanced I/O Controls Single Developer : $1099 Additional Developer : $379 ActiveX & VCL Also Available Plot Pack .Net x Plotting : Scientific, Engineering, Strip-Chart, Digital, EKG, and more ActiveX & VCL Also Available Ultra Pack .Net x 56 Controls x Basic & Advanced I/O Controls plus Plotting Single Developer : $1699 Additional Developer : $579 ActiveX & VCL Also Available Single Developer : $559 Additional Developer : $189 Single Developer : $859 Additional Developer : $289 www.iocomp.com 888-599-2929 +1-407-226-3456 7081 Grand National Drive Suite 112, Orlando, FL 32819 26 Dr. Dobb’s Journal l www.ddj.com l March 2008 http://www.iocomp.com http://www.iocomp.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - March 2008

Dr. Dobb's Journal - March 2008 Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook Social Networks and Software Development Conversations Detecting Bugs in Safety-Critical Code Change Code Without Fear Continuous Integration and Performance Testing Wt: A Web Toolkit Automating Release Notifications The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - March 2008

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