Case Study – Compiler Optimization

They (compiler optimizations) do result in weird things sometimes and here is one such  found with FreeRTOS for ARM Cortex-M3 port. This is as result of “Tail Call Optimization” as I had mentioned it in detail in my last post here.

Such bugs can take a lot of time to debug and still keep you quite clueless because they manifest as if they are HeisenBug.

Nevertheless here is detailed summary of that bug,
http://sourceforge.net/projects/freertos/forums/forum/382005/topic/6928192

*** Update:
To be precise above issue is actually compiler optimization magic coupled with how PendSV is handled by ARM Cortex-M3 NVIC.

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