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AK+Kernel: Eliminate UB (signed overflow) from days_since_epoch

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This commit is contained in:
Ben Wiederhake 2023-01-01 20:07:27 +01:00 • committed by Tim Flynn
parent 7a69219a35
commit 3334cf675a
3 changed files with 20 additions and 16 deletions
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17
Tests/AK/TestTime.cpp
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@ -277,12 +277,12 @@ TEST_CASE(is_negative)
struct YearAndDays {
int year;
int days;
i64 days;
};
TEST_CASE(years_to_days_since_epoch_points)
{
Array<YearAndDays, 22> test_data = { {
Array<YearAndDays, 24> test_data = { {
{ 1969, -365 },
{ 1970, 0 },
{ 1971, 365 },
@ -306,11 +306,14 @@ TEST_CASE(years_to_days_since_epoch_points)
{ 5881474, 2147444740 },
// Very important year: https://github.com/SerenityOS/serenity/pull/16760#issuecomment-1369054745
{ -999999, -365961662 },
// The following two values haven't been verified by any other algorithm, but are very close to "year * 365.2425", and prove that there is no UB due to signed overflow:
{ 2147483647, 784351576412 },
{ -2147483648, -784353015833 },
} };
for (auto entry : test_data) {
int year = entry.year;
int expected_days = entry.days;
int actual_days = years_to_days_since_epoch(year);
i64 expected_days = entry.days;
i64 actual_days = years_to_days_since_epoch(year);
EXPECT_EQ(actual_days, expected_days);
}
}
@ -319,7 +322,7 @@ BENCHMARK_CASE(years_to_days_since_epoch_benchmark)
{
// This benchmark takes consistently "0ms" on Linux, and "0ms" on Serenity.
for (size_t i = 0; i < 100; ++i) {
int actual_days = years_to_days_since_epoch(-5877640);
i64 actual_days = years_to_days_since_epoch(-5877640);
(void)actual_days;
EXPECT_EQ(actual_days, -2147483456);
}
@ -467,8 +470,8 @@ TEST_CASE(years_to_days_since_epoch_span)
// clang-format on
for (size_t offset = 0; offset < test_data.size(); ++offset) {
int year = offset + test_data_start_year;
int expected_days = test_data[offset];
int actual_days = years_to_days_since_epoch(year);
i64 expected_days = test_data[offset];
i64 actual_days = years_to_days_since_epoch(year);
EXPECT_EQ(actual_days, expected_days);
}
}