Express Logic has introduced a new development tool that helps developers avoid stack overflow problems in embedded systems.
The new tool, StackX, performs a comprehensive analysis of a complete application at the executable code level, computing the worst-case stack usage the application can experience.
In the C programming language, the stack – a region of memory on which local variables are created and function arguments are passed – is allocated memory by the programmer, with the amount based on factors such as machine architecture, OS, application design and amount of memory available. When the program requires more memory for its stack than has been allocated, the stack overflows – without warning in most cases – which can corrupt other memory areas and typically results in a program crash. Such crashes are very difficult to trace back to the stack overflow, causing programmers to expend considerable time and energy to find the overflow. As a result, they tend to over-allocate stack memory as a precaution.
Deciding how much memory to allocate for the stack has been a trial and error process. As widely respected industry commentator and consultant, Jack Ganssle, has observed: “With experience, one learns the standard, scientific way to compute the proper size for a stack: pick a size at random and hope.”
StackX computes the required stack size automatically for developers, enabling them to allocate just the amount of memory needed to be safe, and avoid wasting any additional, unnecessary memory. The tool analyses a program’s executable file (.elf), mapping all function calls, interrupt service routines, local variables and any other factors related to stack usage. This enables it to calculate each thread’s maximum stack memory requirements and produce a ‘call tree’ that shows the maximum stack usage for each thread. Developers can see their program flow and are better able to optimise their code.
StackX employs a proprietary, patent-pending algorithm that is accurate, efficient, and only requires an elf file. While it may be used with any elf file, StackX has particular visibility into ThreadX RTOS-based applications, with its thread-aware stack size calculation. It recognises recursion conditions, where infinite memory would be required to avoid potential overflow, so programmers can correct the code, rather than attempt to allocate more memory.
For more information visit www.rtos.com
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