Imagecraft c compiler and development environment for the atmel avr

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ICCV8 for AVR – C Compiler for Atmel AVRStack Checking FunctionsSeveral library functions are provided for checking stack overflows. Consider thefollowing memory map; if the hardware stack grows into the software stack, thecontent of the software stack changes. This alters the value of local variables andother stacked items. Since the hardware stack is used for function return addresses,this may happen if your function call tree nests too deeply.Likewise, a software stack overflow into the data areas would modify global variablesor other statically allocated items (or Heap items if you use dynamically allocatedmemory). This may happen if you declare too many local variables or if a localaggregate variable is too large.If you use the function printf a lot, the format strings can take up a lot of space inthe data area. This could also contribute to stack overflow. See Strings.high addressHW StacksentinelSW StacksentinelData Areaslow addressSummaryTo use the stack checking functions:1. #include 106
ICCV8 for AVR – C Compiler for Atmel AVR2. Insert _StackCheck(); in your code where you want to check the stacks foroverflow. This may be anywhere in your code, e.g. inside your Watchdog Timerfunction.3. When _StackCheck() detects a stack overflow, it calls the function_StackOverflowed() with an integer argument with a value of 1 to indicatethat the hardware stack has overflowed, and a value of 0 to indicate that thesoftware stack has overflowed.4. The default _StackOverflowed() library function jumps to location 0 andresets the program. To change this default behavior, write your own_StackOverflowed function in your source code. This will override the defaultone. For program debugging, your _StackOverflowed function should dosomething to indicate a catastrophic condition, perhaps by blinking a LED. If youare using a debugger, you can set a breakpoint at the _StackOverflowedfunction to see if it gets called.The prototypes for these two functions are listed in the header file AVRdef.h.SentinelsThe startup code writes a sentinel byte at the address just above the data area and asimilar byte at the address just above the software stack. If the sentinel bytes getchanged, then a stack overflow has occurred.Note that if you are using dynamic memory allocation, you must skip the sentinel byteat _bss_end for your heap allocation. See Standard Library And Memory AllocationFunctions.107
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TOOL REFERENCESMISRA / Lint Code Ch
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