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time: fix quickcheck test to avoid wraparounds

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When we call time.Unix(s, ns), the internal representation is
s + 62135596800,  where 62135596800 is the number of
seconds from Jan 1 1 to Jan 1 1970.

If quickcheck generates numbers too close to 2^63,
the addition can wraparound to make a very negative
internal 64-bit value. Wraparounds are not guarded
against, since they would not arise in any reasonable program,
so just avoid testing near them.

Fixes #52409.

Change-Id: Id466c8a34a49055ab26f2687a6b2b657cb64bed6
Reviewed-on: https://go-review.googlesource.com/c/go/+/402177
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Russ Cox 2022-04-25 14:06:10 -04:00 committed by Gopher Robot
parent 09ada1af8f
commit 17d7983b29
1 changed files with 11 additions and 0 deletions
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11
src/time/time_test.go
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@ -281,6 +281,8 @@ func TestTruncateRound(t *testing.T) {
b1e9.SetInt64(1e9)
testOne := func(ti, tns, di int64) bool {
t.Helper()
t0 := Unix(ti, int64(tns)).UTC()
d := Duration(di)
if d < 0 {
@ -367,6 +369,13 @@ func TestTruncateRound(t *testing.T) {
for i := 0; i < int(b); i++ {
d *= 5
}
// Make room for unix ↔ internal conversion.
// We don't care about behavior too close to ± 2^63 Unix seconds.
// It is full of wraparounds but will never happen in a reasonable program.
// (Or maybe not? See go.dev/issue/20678. In any event, they're not handled today.)
ti >>= 1
return testOne(ti, int64(tns), int64(d))
}
quick.Check(f1, cfg)
@ -377,6 +386,7 @@ func TestTruncateRound(t *testing.T) {
if d < 0 {
d = -d
}
ti >>= 1 // see comment in f1
return testOne(ti, int64(tns), int64(d))
}
quick.Check(f2, cfg)
@ -399,6 +409,7 @@ func TestTruncateRound(t *testing.T) {
// full generality
f4 := func(ti int64, tns int32, di int64) bool {
ti >>= 1 // see comment in f1
return testOne(ti, int64(tns), di)
}
quick.Check(f4, cfg)