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8.2.2.2. Running in a Restricted Environment
For more information about identifying these API functions that are not available to ISRs, refer to the HAL API Reference chapter.
Be careful when calling ANSI C standard library functions inside of an ISR. Avoid using the C standard library I/O API, because calling these functions can result in deadlock within the system, that is, the system can become permanently blocked in the ISR.
In particular, do not call printf() from within an ISR unless you are certain that stdout is mapped to a non-interrupt-based device driver. Otherwise, printf() can deadlock the system, waiting for a hardware interrupt that never occurs because interrupts are disabled.