SDK13 nrf_drv_rtc_init bug!

[Nguyen Hoan Hoang]

Line 73 in function nrf_drv_rtc_init snippet bellow checks for UNINIT state. It accesses the m_cb array which is an uninitialized global. That condition would intermittently fail.

if (m_cb[p_instance->instance_id].state != NRF_DRV_STATE_UNINITIALIZED)
{
    err_code = NRF_ERROR_INVALID_STATE;
    NRF_LOG_WARNING("Function: %s, error code: %s.\r\n", (uint32_t)__func__, (uint32_t)ERR_TO_STR(err_code));
    return err_code;
}

[Ole Bauck]

All global and static variables will be initialized to zero. NRF_DRV_STATE_UNINITIALIZED is zero.

[Nguyen Hoan Hoang]

Could you tell me when would that happen ? Am I missing an init somewhere ?

This will not guaranty to be initialized to zero.

static nrf_drv_rtc_cb_t      m_cb[ENABLED_RTC_COUNT];

This will

static nrf_drv_rtc_cb_t      m_cb[ENABLED_RTC_COUNT] = {{0,},};

[Ole Bauck]

This is a C feature, all global and static variables will automatically be initialized to zero, just do a search on it and you will find a lot of answers on stack overflow ;) It is normal to check if the variable is 0 or NULL to see if it is initialized.

These variables will be a part of the Zero Initialized data in RAM as described in this blog: devzone.nordicsemi.com/.../

[Ole Bauck]

stackoverflow.com/.../are-global-variables-always-initalized-to-zero-in-c

[Nguyen Hoan Hoang]

It does not seems to be so when compiled with gcc. I get non zero value. This happens when I enable NRF_LOG. It is zero when NRF_LOG is disabled.