From 1d3b54c784da260f71d885f5f560d69c211a645e Mon Sep 17 00:00:00 2001 From: Flavio Toffalini Date: Mon, 26 Oct 2026 09:03:57 +0000 Subject: plist: fix the (sec, usec) date API round trip plist_set_date_val stores val = sec + usec / 1000000, but plist_get_date_val splits it with a truncating cast and fabs(): *sec = (int32_t)val; val = fabs((val - (int64_t)val) * 1000000); *usec = (int32_t)val; Two results are wrong. The product is truncated, so set(5, 6) reads back as (5, 5) - 29.3% of round trips over sec in [0, 3] come back a microsecond short. And for a negative value, truncation toward zero plus fabs() give a pair that does not denote the same instant: set(-3, 250000) stores -2.75 and reads back as (-2, 750000), which the setter would store as -1.25. Every round trip with sec < 0 and usec != 0 is wrong. (int32_t)val is also undefined when the stored value is outside the int32_t range. Round the seconds down, round the fraction to microseconds carrying 1000000 into the seconds, and clamp the seconds before converting, so sec + usec / 1000000 == val to the microsecond with 0 <= usec < 1000000 - the convention the setter uses. Add test/date_val.c covering fixed cases and a sweep over sec in [-2, 2]. It fails on an unmodified tree - set(5, 6), set(-3, 250000) and set(-1, 1) all come back as different instants - and passes with this change, with make check at 44/44. Co-Authored-By: Claude Opus 5 Claude-Session: https://claude.ai/code/session_01Arn4YaWtcQBDsQuJtyBmFP --- test/date_val.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 test/date_val.c (limited to 'test/date_val.c') diff --git a/test/date_val.c b/test/date_val.c new file mode 100644 index 0000000..127e194 --- /dev/null +++ b/test/date_val.c @@ -0,0 +1,42 @@ +#include +#include +#include + +/* plist_get_date_val must return exactly what plist_set_date_val stored, + * including dates before the epoch (negative seconds). */ + +#if defined(__GNUC__) || defined(__clang__) +#pragma GCC diagnostic ignored "-Wdeprecated-declarations" +#endif + +static int check(int32_t sec, int32_t usec) +{ + int32_t s = 0, u = 0; + plist_t d = plist_new_date(0, 0); + plist_set_date_val(d, sec, usec); + plist_get_date_val(d, &s, &u); + plist_free(d); + if (s != sec || u != usec) { + printf("set(%d, %d) -> get(%d, %d)\n", sec, usec, s, u); + return 1; + } + return 0; +} + +int main(int argc, char** argv) +{ + int err = 0; + int32_t sec, usec; + + err |= check(5, 6); + err |= check(0, 999999); + err |= check(-3, 250000); + err |= check(-1, 1); + err |= check(1000000000, 123456); + for (sec = -2; sec <= 2 && !err; sec++) { + for (usec = 0; usec < 1000000 && !err; usec += 7) { + err |= check(sec, usec); + } + } + return err; +} -- cgit v1.1-32-gdbae