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pico_time comment changes: remove stale comment, include warning about integer overflow

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graham sanderson 2021-01-28 08:06:27 -06:00 committed by Graham Sanderson
parent 5bd926ff5e
commit f8cef7a9b5
2 changed files with 5 additions and 2 deletions
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6
src/common/pico_time/include/pico/time.h
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@ -143,9 +143,13 @@ static inline absolute_time_t make_timeout_time_ms(uint32_t ms) {
/*! \brief Return the difference in microseconds between two timestamps /*! \brief Return the difference in microseconds between two timestamps
* \ingroup timestamp * \ingroup timestamp
* *
* \note be careful when diffing against large timestamps (e.g. \ref at_the_end_of_time)
* as the signed integer may overflow.
*
* \param from the first timestamp * \param from the first timestamp
* \param to the second timestamp * \param to the second timestamp
* \return the number of microseconds between the two timestamps (positive if `to` is after `from`) * \return the number of microseconds between the two timestamps (positive if `to` is after `from` except
* in case of overflow)
*/ */
static inline int64_t absolute_time_diff_us(absolute_time_t from, absolute_time_t to) { static inline int64_t absolute_time_diff_us(absolute_time_t from, absolute_time_t to) {
return to_us_since_boot(to) - to_us_since_boot(from); return to_us_since_boot(to) - to_us_since_boot(from);

1
src/common/pico_time/time.c
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@ -14,7 +14,6 @@
#include "hardware/gpio.h" #include "hardware/gpio.h"
const absolute_time_t ABSOLUTE_TIME_INITIALIZED_VAR(nil_time, 0); const absolute_time_t ABSOLUTE_TIME_INITIALIZED_VAR(nil_time, 0);
// use LONG_MAX not ULONG_MAX so we don't have sign overflow in time diffs
const absolute_time_t ABSOLUTE_TIME_INITIALIZED_VAR(at_the_end_of_time, ULONG_MAX); const absolute_time_t ABSOLUTE_TIME_INITIALIZED_VAR(at_the_end_of_time, ULONG_MAX);
typedef struct alarm_pool_entry { typedef struct alarm_pool_entry {