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std.cache_hash: temporary workaround for mtime precision on linux

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See #6082
This commit is contained in:
Andrew Kelley 2020-08-18 01:30:03 -07:00
parent 56c81c713f
commit c0517bf1f6
1 changed files with 9 additions and 11 deletions
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20
lib/std/cache_hash.zig
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@ -451,10 +451,17 @@ fn isProblematicTimestamp(fs_clock: i128) bool {
// to detect precision of seconds, because looking at the zero bits in base
// 2 would not detect precision of the seconds value.
const fs_sec = @intCast(i64, @divFloor(fs_clock, std.time.ns_per_s));
const fs_nsec = @intCast(i64, @mod(fs_clock, std.time.ns_per_s));
var fs_nsec = @intCast(i64, @mod(fs_clock, std.time.ns_per_s));
var wall_sec = @intCast(i64, @divFloor(wall_clock, std.time.ns_per_s));
var wall_nsec = @intCast(i64, @mod(wall_clock, std.time.ns_per_s));
if (std.Target.current.os.tag == .linux) {
// TODO As a temporary measure while we figure out how to solve
// https://github.com/ziglang/zig/issues/6082, we cut the granularity of nanoseconds
// by a large amount.
fs_nsec &= @as(i64, -1) << 23;
}
// First make all the least significant zero bits in the fs_clock, also zero bits in the wall clock.
if (fs_nsec == 0) {
wall_nsec = 0;
@ -466,16 +473,7 @@ fn isProblematicTimestamp(fs_clock: i128) bool {
} else {
wall_nsec &= @as(i64, -1) << @intCast(u6, @ctz(i64, fs_nsec));
}
if (wall_nsec == fs_nsec and wall_sec == fs_sec)
return true;
// I have also observed precision problems at a millisecond granularity.
const fs_msec = @intCast(i64, @divFloor(fs_clock, std.time.ns_per_ms * 2));
const wall_msec = @intCast(i64, @divFloor(wall_clock, std.time.ns_per_ms * 2));
if (fs_msec == wall_msec)
return true;
return false;
return wall_nsec == fs_nsec and wall_sec == fs_sec;
}
test "cache file and then recall it" {