time.add_days(1) jumps from 2013-05-01 to 1970-01-02

[gmlewis]

Describe the bug

Using V 0.3.2 9a86456, I wrote the following program:

module main

import time

fn main() {
	t := time.Time{
		year: 2013
		month: 5
		day: 1
	}
	println('BEFORE: ${t} is a ${t.long_weekday_str()}: ${t.debug()}')
	t2 := t.add_days(1)
	println('AFTER: ${t2} is a ${t2.long_weekday_str()}: ${t2.debug()}')
}

and ran it on my Linux Mint Cinnamon 20.3 box:

v version && v run bug.v
V 0.3.2 9a86456
BEFORE: 2013-05-01 00:00:00 is a Wednesday: Time{ year: 2013 month: 05 day: 01 hour: 00 minute: 00 second: 00 microsecond: 000000 unix: 0000000 }
AFTER: 1970-01-02 00:00:00 is a Friday: Time{ year: 1970 month: 01 day: 02 hour: 00 minute: 00 second: 00 microsecond: 000000 unix: 0086400 }

Expected Behavior

I expected to see 2013-05-02.

Current Behavior

I got: 1970-01-02.

Reproduction Steps

module main

import time

fn main() {
	t := time.Time{
		year: 2013
		month: 5
		day: 1
	}
	println('BEFORE: ${t} is a ${t.long_weekday_str()}: ${t.debug()}')
	t2 := t.add_days(1)
	println('AFTER: ${t2} is a ${t2.long_weekday_str()}: ${t2.debug()}')
}

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.3.2 9a86456

Environment details (OS name and version, etc.)

OS: linux, Linux Mint 20.3
Processor: 4 cpus, 64bit, little endian, Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
CC version: cc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0

getwd: /home/glenn/exercism/vlang/meetup
vmodules: /home/glenn/.vmodules
vroot: /home/glenn/src/github.com/vlang/v
vexe: /home/glenn/src/github.com/vlang/v/v
vexe mtime: 2023-01-29 02:00:22
is vroot writable: true
is vmodules writable: true
V full version: V 0.3.2 148d578.9a86456

Git version: git version 2.25.1
Git vroot status: weekly.2022.29-1224-g9a864563 (6 commit(s) behind V master)
.git/config present: true
thirdparty/tcc status: thirdparty-linux-amd64 12f392c3

[JalonSolov]

This is a case of V's default initialization combined with no constructors, is causing a problem.

The key is in the output: unix: 0000000 for your initial Time.

add_days adds values to the unix field, which in this case is 0, instead of a representation of the number of seconds from 1970-01-01. So when it adds a day, you get 1970-01-02, which is what you saw for the value in t2.

This one will be... interesting to fix.

[yuyi98]

module main

import time

fn main() {
	t := time.new_time(
		year: 2013
		month: 5
		day: 1
	)
	println('BEFORE: ${t} is a ${t.long_weekday_str()}: ${t.debug()}')
	t2 := t.add_days(1)
	println('AFTER: ${t2} is a ${t2.long_weekday_str()}: ${t2.debug()}')
}

PS D:\Test\v\tt1> v run .
BEFORE: 2013-05-01 00:00:00 is a Wednesday: Time{ year: 2013 month: 05 day: 01 hour: 00 minute: 00 second: 00 microsecond: 000000 unix: 1367366400 }    
AFTER: 2013-05-02 00:00:00 is a Thursday: Time{ year: 2013 month: 05 day: 02 hour: 00 minute: 00 second: 00 microsecond: 000000 unix: 1367452800 }  

We should disallow the direct use of structs to initialize values.