8000 utime: ticks_diff() raises an exception with large values returned by ticks_us() or ticks_ms() · Issue #113 · pycom/pycom-micropython-sigfox · GitHub
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utime: ticks_diff() raises an exception with large values returned by ticks_us() or ticks_ms() #113

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robert-hh opened this issue Dec 25, 2017 · 4 comments
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utime: ticks_diff() raises an exception with large values returned by ticks_us() or ticks_ms() #113

robert-hh opened this issue Dec 25, 2017 · 4 comments

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@robert-hh
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robert-hh commented Dec 25, 2017 •
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The functions utime.ticks_us() and utime.ticks_ms() may return values, which then cannot be used as input for utime.ticks_diff(). Example:

>>> time.ticks_us()
3636776263
>>> time.ticks_diff(time.ticks_us(), time.ticks_us()+1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: overflow converting long int to machine word
>>>

The reason is, that the return values are not stripped to values which can be representef by a MP_SMALL_INT, or at least 31 bit.
Edit: Funny enough, the utime module is mostly implemented twice, in esp32/mods/modutime.c and in py/extmod/mphal_utime.c, where the latter seems to have proper value/overflow handling.
@robert-hh robert-hh mentioned this issue Dec 25, 2017
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@robert-hh
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Made a PR attemting to fix that issue.

@robert-hh robert-hh changed the title utime: Inconsistency in value ranges utime: ticks_diff() raises an exception with large values returned by ticks_us() or ticks_ms() Jan 3, 2018
@robert-hh
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This simple script will trigger an exception latest after about 35 minutes.

import utime

new = utime.ticks_us()
while True:
    utime.sleep(1)
    old = new
    new = utime.ticks_us()
    print(new, utime.ticks_diff(old,new))

@robert-hh
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Actually the minimal change to fix that is to modify ticks_diff() as:

STATIC mp_obj_t time_ticks_diff(mp_obj_t start_in, mp_obj_t end_in) {
    int32_t start = mp_obj_get_int_truncated(start_in);
    int32_t end = mp_obj_get_int_truncated(end_in);
    return mp_obj_new_int((end - start));
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(time_ticks_diff_obj, time_ticks_diff);

This change will also return a reasonable behavior, if the arguments of the call are swapped - sign change. The only deviating result is achieved with ticks_diff(0x80000000, 0), and ticks_diff(0, 0x8000000), which return the same value -2147483648

@robert-hh
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Thanks for merging.

@martijnthe martijnthe mentioned this issue Dec 5, 2018
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peter-pycom pushed a commit that referenced this issue May 4, 2020
@Xykon
Merge pull request #113 from pycom/secure_boot_fix_sdkconfig_copy
20cc45c 
Update get_idf_libs.py
X-Ryl669 pushed a commit to X-Ryl669/pycom-micropython-sigfox that referenced this issue May 12, 2023
@robert-hh
esp32/mods/modutime.c: Ensure proper smallint values on overflow
8d573e5 
This fixes ensure, that the return values of ticks_ms(), ticks_us() and ticks_cpu() fit into a MP_SMALL_INT. That way, they can be fed into ticks_diff() without the risk of an OverflowError (see issue pycom#113). As a side effect, the result of ticks_diff(a, b) is always defined as a reasonable value even if a is a time after b (a > b). In that case, the value is negative. The implementation just copies the mechanism from py/extmod/mphal_utime.c.
Second change: Add the method ticks_add().
X-Ryl669 pushed a commit to X-Ryl669/pycom-micropython-sigfox that referenced this issue May 12, 2023
@Xykon
Merge pull request pycom#113 from pycom/secure_boot_fix_sdkconfig_copy
e041fda 
Update get_idf_libs.py
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