{"action":"created","issue":{"url":"https://api.github.com/repos/rust-lang/cargo/issues/2874","repository_url":"https://api.github.com/repos/rust-lang/cargo","labels_url":"https://api.github.com/repos/rust-lang/cargo/issues/2874/labels{/name}","comments_url":"https://api.github.com/repos/rust-lang/cargo/issues/2874/comments","events_url":"https://api.github.com/repos/rust-lang/cargo/issues/2874/events","html_url":"https://github.com/rust-lang/cargo/issues/2874","id":165556505,"number":2874,"title":"Nanosecond-granularity modification times cause spurious rebuilds","user":{"login":"shepmaster","id":174509,"avatar_url":"https://avatars.githubusercontent.com/u/174509?v=3","gravatar_id":"","url":"https://api.github.com/users/shepmaster","html_url":"https://github.com/shepmaster","followers_url":"https://api.github.com/users/shepmaster/followers","following_url":"https://api.github.com/users/shepmaster/following{/other_user}","gists_url":"https://api.github.com/users/shepmaster/gists{/gist_id}","starred_url":"https://api.github.com/users/shepmaster/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/shepmaster/subscriptions","organizations_url":"https://api.github.com/users/shepmaster/orgs","repos_url":"https://api.github.com/users/shepmaster/repos","events_url":"https://api.github.com/users/shepmaster/events{/privacy}","received_events_url":"https://api.github.com/users/shepmaster/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":1,"created_at":"2016-07-14T13:00:56Z","updated_at":"2016-07-14T13:28:53Z","closed_at":null,"body":"I have a large `Cargo.toml` that I'm placing in a Docker container and prebuilding all the dependencies. However, at runtime there's still one crate that is rebuilt: `tempfile v2.1.4`. Turning on logging shows: \r\n\r\n> INFO:cargo::ops::cargo_rustc::fingerprint: fingerprint error for tempfile v2.1.4: mtime based comopnents have changed: Some(FileTime { seconds: 1468471990, nanos: 0 }) != Some(FileTime { seconds: 1468471990, nanos: 914840077 }), paths are \"/playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\" and \"/playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\"\r\n\r\nMore specifically:\r\n\r\n```rust\r\nSome(FileTime { seconds: 1468471990, nanos: 0 })\r\nSome(FileTime { seconds: 1468471990, nanos: 914840077 })\r\n```\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/rust-lang/cargo/issues/comments/232665175","html_url":"https://github.com/rust-lang/cargo/issues/2874#issuecomment-232665175","issue_url":"https://api.github.com/repos/rust-lang/cargo/issues/2874","id":232665175,"user":{"login":"shepmaster","id":174509,"avatar_url":"https://avatars.githubusercontent.com/u/174509?v=3","gravatar_id":"","url":"https://api.github.com/users/shepmaster","html_url":"https://github.com/shepmaster","followers_url":"https://api.github.com/users/shepmaster/followers","following_url":"https://api.github.com/users/shepmaster/following{/other_user}","gists_url":"https://api.github.com/users/shepmaster/gists{/gist_id}","starred_url":"https://api.github.com/users/shepmaster/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/shepmaster/subscriptions","organizations_url":"https://api.github.com/users/shepmaster/orgs","repos_url":"https://api.github.com/users/shepmaster/repos","events_url":"https://api.github.com/users/shepmaster/events{/privacy}","received_events_url":"https://api.github.com/users/shepmaster/received_events","type":"User","site_admin":false},"created_at":"2016-07-14T13:28:53Z","updated_at":"2016-07-14T13:28:53Z","body":"This may be a Docker-specific issue, but I'm unclear as to why it would only happen with the one crate. If I watch the modification times, it appears that the filesystem truncates the modification time between images:\r\n\r\n\r\n```dockerfile\r\nRUN cargo build && ls --full-time /playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\r\n\r\nRUN ls --full-time /playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\r\n```\r\n\r\n```\r\n-rw-r--r-- 1 root root 60 2016-07-14 13:26:37.779155991 +0000 /playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\r\n\r\n-rw-r--r-- 1 root root 60 2016-07-14 13:26:37.000000000 +0000 /playground/target/debug/build/tempfile-1b82f6307d61d5f0/output\r\n```"}}
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