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breadcrumb

A small marker in memory that survives a crash and says what the program was doing.

A breadcrumb is a stage marker kept in RTC no-init memory (RTC_NOINIT_ATTR) that survives a software reset but not a power cut, read at the next boot to locate a crash.

Examples

  • A fan controller writes stages like "joining Wi-Fi" or "flushing queue" into an RTC_NOINIT_ATTR variable, and after a panic the next boot reports the last one.

  • A breadcrumb survives a panic or watchdog reset but not a power cut, so it is only read when the reset reason says crash.

See also

crash report heartbeat rollback
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