[INFO] cloning repository https://github.com/mnwww/rustdesk [INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/mnwww/rustdesk" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmnwww%2Frustdesk", kill_on_drop: false }` [INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmnwww%2Frustdesk'... [INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }` [INFO] [stdout] 7df1a40895ee2008ed529b97d4d69ad226fd4f5b [INFO] checking mnwww/rustdesk against master#5257aee7dd163d21d32fa904578d4fb0f4c91b79 for pr-116494-2 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmnwww%2Frustdesk" "/workspace/builds/worker-6-tc1/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-6-tc1/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/mnwww/rustdesk on toolchain 5257aee7dd163d21d32fa904578d4fb0f4c91b79 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+5257aee7dd163d21d32fa904578d4fb0f4c91b79" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] removed /workspace/builds/worker-6-tc1/source/.cargo/config.toml [INFO] started tweaking git repo https://github.com/mnwww/rustdesk [INFO] finished tweaking git repo https://github.com/mnwww/rustdesk [INFO] tweaked toml for git repo https://github.com/mnwww/rustdesk written to /workspace/builds/worker-6-tc1/source/Cargo.toml [INFO] crate git repo https://github.com/mnwww/rustdesk already has a lockfile, it will not be regenerated [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+5257aee7dd163d21d32fa904578d4fb0f4c91b79" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] [stderr] Blocking waiting for file lock on package cache [ERROR] error running command: no output for 300 seconds [ERROR] this task or one of its parent failed! [ERROR] no output for 300 seconds [ERROR] note: run with `RUST_BACKTRACE=1` to display a backtrace. [INFO] checking mnwww/rustdesk against try#d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8 for pr-116494-2 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmnwww%2Frustdesk" "/workspace/builds/worker-6-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-6-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/mnwww/rustdesk on toolchain d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] removed /workspace/builds/worker-6-tc2/source/.cargo/config.toml [INFO] started tweaking git repo https://github.com/mnwww/rustdesk [INFO] finished tweaking git repo https://github.com/mnwww/rustdesk [INFO] tweaked toml for git repo https://github.com/mnwww/rustdesk written to /workspace/builds/worker-6-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/mnwww/rustdesk already has a lockfile, it will not be regenerated [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] [stderr] Blocking waiting for file lock on package cache [INFO] [stderr] Updating crates.io index [INFO] [stderr] Updating git repository `https://github.com/21pages/hwcodec` [INFO] [stderr] Updating git repository `https://github.com/open-trade/confy` [INFO] [stderr] Updating git repository `https://github.com/open-trade/tokio-socks` [INFO] [stderr] Updating git repository `https://github.com/21pages/machine-uid` [INFO] [stderr] Updating git repository `https://github.com/fufesou/rdev` [INFO] [stderr] Updating git repository `https://github.com/fufesou/The-Fat-Controller` [INFO] [stderr] Updating git repository `https://github.com/rustdesk/magnum-opus` [INFO] [stderr] Updating git repository `https://github.com/open-trade/parity-tokio-ipc` [INFO] [stderr] Updating git repository `https://github.com/rustdesk-org/reqwest` [INFO] [stderr] Updating git repository `https://github.com/rustdesk-org/keepawake-rs` [INFO] [stderr] Updating git repository `https://github.com/rustdesk-org/tao` [INFO] [stderr] Updating git repository `https://github.com/open-trade/rust-sciter` [INFO] [stderr] Updating git repository `https://github.com/fufesou/evdev` [INFO] [stderr] Updating git repository `https://github.com/fufesou/mouce.git` [INFO] [stderr] Updating git repository `https://github.com/fufesou/pam` [INFO] [stderr] Updating git repository `https://github.com/open-trade/pulsectl` [INFO] [stderr] Updating git repository `https://github.com/21pages/impersonate-system` [INFO] [stderr] Updating git repository `https://github.com/bjornsnoen/x11-rs` [INFO] [stderr] Blocking waiting for file lock on package cache [INFO] [stderr] Downloading crates ... [INFO] [stderr] Downloaded wol-rs v1.0.0 [INFO] [stderr] Downloaded osascript v0.3.0 [INFO] [stderr] Downloaded tray-icon v0.11.3 [INFO] [stderr] Downloaded netlink-packet-core v0.5.0 [INFO] [stderr] Downloaded apple-bindgen v0.2.0 [INFO] [stderr] Downloaded build-target v0.4.0 [INFO] [stderr] Downloaded dlopen2_derive v0.2.0 [INFO] [stderr] Downloaded cidr-utils v0.5.10 [INFO] [stderr] Downloaded dbus-crossroads v0.5.2 [INFO] [stderr] Downloaded tzdb v0.5.7 [INFO] [stderr] Downloaded netlink-packet-route v0.15.0 [INFO] [stderr] Downloaded dart-sys v4.0.2 [INFO] [stderr] Downloaded flutter_rust_bridge v1.75.3 [INFO] [stderr] Downloaded flutter_rust_bridge_codegen v1.75.3 [INFO] [stderr] Downloaded toml v0.6.0 [INFO] [stderr] Downloaded apple-sdk v0.4.0 [INFO] [stderr] Downloaded rubato v0.12.0 [INFO] [stderr] Downloaded gstreamer-app-sys v0.9.1 [INFO] [stderr] Downloaded gstreamer v0.16.7 [INFO] [stderr] Downloaded gstreamer-base v0.16.5 [INFO] [stderr] Downloaded gstreamer-base-sys v0.9.1 [INFO] [stderr] Downloaded gstreamer-video v0.16.7 [INFO] [stderr] Downloaded webm-sys v1.0.3 [INFO] [stderr] Downloaded system_shutdown v4.0.1 [INFO] [stderr] Downloaded flexi_logger v0.25.4 [INFO] [stderr] Downloaded sysinfo v0.29.6 [INFO] [stderr] Downloaded default-net v0.14.1 [INFO] [stderr] Downloaded allo-isolate v0.1.14 [INFO] [stderr] Downloaded flutter_rust_bridge_macros v1.75.3 [INFO] [stderr] Downloaded fruitbasket v0.10.0 [INFO] [stderr] Downloaded libsamplerate-sys v0.1.12 [INFO] [stderr] Downloaded os-version v0.2.0 [INFO] [stderr] Downloaded pam-sys v1.0.0-alpha4 [INFO] [stderr] Downloaded miow v0.5.0 [INFO] [stderr] Downloaded realfft v3.2.0 [INFO] [stderr] Downloaded gstreamer-app v0.16.5 [INFO] [stderr] Downloaded pretty-hex v0.2.1 [INFO] [stderr] Downloaded gstreamer-sys v0.9.1 [INFO] [stderr] Downloaded rpassword v2.1.0 [INFO] [stderr] Downloaded windows-interface v0.52.0 [INFO] [stderr] Downloaded libappindicator v0.9.0 [INFO] [stderr] Downloaded dlopen2 v0.4.1 [INFO] [stderr] Downloaded delegate v0.8.0 [INFO] [stderr] Downloaded shared_memory v0.12.4 [INFO] [stderr] Downloaded keyboard-types v0.7.0 [INFO] [stderr] Downloaded runas v1.0.0 [INFO] [stderr] Downloaded quest v0.3.0 [INFO] [stderr] Downloaded repng v0.2.2 [INFO] [stderr] Downloaded webm v1.0.2 [INFO] [stderr] Downloaded win-sys v0.3.1 [INFO] [stderr] Downloaded gdkwayland-sys v0.18.0 [INFO] [stderr] Downloaded apple-sys v0.2.0 [INFO] [stderr] Downloaded shadow-rs v0.21.0 [INFO] [stderr] Downloaded pam-macros v0.0.3 [INFO] [stderr] Downloaded enum-map v2.5.0 [INFO] [stderr] Downloaded epoll v4.3.1 [INFO] [stderr] Downloaded samplerate v0.2.4 [INFO] [stderr] Downloaded android_logger v0.13.1 [INFO] [stderr] Downloaded muldiv v0.2.1 [INFO] [stderr] Downloaded gstreamer-video-sys v0.9.1 [INFO] [stderr] Downloaded sys-locale v0.3.0 [INFO] [stderr] Downloaded gdkx11-sys v0.18.0 [INFO] [stderr] Downloaded windows-implement v0.52.0 [INFO] [stderr] Downloaded libappindicator-sys v0.9.0 [INFO] [stderr] Downloaded muda v0.11.4 [INFO] [stderr] Downloaded protobuf-codegen v3.2.0 [INFO] [stderr] Downloaded windows-service v0.6.0 [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 688b6fb25275029305fe64af15565e3aa2bcf4e4b1d8234700e35de13104e3f8 [INFO] running `Command { std: "docker" "start" "-a" "688b6fb25275029305fe64af15565e3aa2bcf4e4b1d8234700e35de13104e3f8", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "688b6fb25275029305fe64af15565e3aa2bcf4e4b1d8234700e35de13104e3f8", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "688b6fb25275029305fe64af15565e3aa2bcf4e4b1d8234700e35de13104e3f8", kill_on_drop: false }` [INFO] [stdout] 688b6fb25275029305fe64af15565e3aa2bcf4e4b1d8234700e35de13104e3f8 [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=forbid" "-e" "RUSTDOCFLAGS=--cap-lints=forbid" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }` [INFO] [stdout] 4445f0defc1fa97159ebe85f4ef170034c5e9435cc552c304b51513c53706fbb [INFO] running `Command { std: "docker" "start" "-a" "4445f0defc1fa97159ebe85f4ef170034c5e9435cc552c304b51513c53706fbb", kill_on_drop: false }` [INFO] [stderr] Compiling libc v0.2.144 [INFO] [stderr] Compiling proc-macro2 v1.0.63 [INFO] [stderr] Compiling unicode-ident v1.0.8 [INFO] [stderr] Compiling quote v1.0.27 [INFO] [stderr] Compiling serde v1.0.163 [INFO] [stderr] Compiling pkg-config v0.3.27 [INFO] [stderr] Compiling syn v1.0.109 [INFO] [stderr] Compiling memchr v2.5.0 [INFO] [stderr] Compiling hashbrown v0.12.3 [INFO] [stderr] Compiling log v0.4.17 [INFO] [stderr] Compiling thiserror v1.0.40 [INFO] [stderr] Compiling cfg-if v1.0.0 [INFO] [stderr] Compiling futures-core v0.3.28 [INFO] [stderr] Checking pin-project-lite v0.2.9 [INFO] [stderr] Compiling indexmap v1.9.3 [INFO] [stderr] Compiling slab v0.4.8 [INFO] [stderr] Compiling crossbeam-utils v0.8.15 [INFO] [stderr] Compiling futures-util v0.3.28 [INFO] [stderr] Checking once_cell v1.17.1 [INFO] [stderr] Compiling winnow v0.4.6 [INFO] [stderr] Compiling bitflags v1.3.2 [INFO] [stderr] Checking futures-io v0.3.28 [INFO] [stderr] Compiling io-lifetimes v1.0.10 [INFO] [stderr] Checking futures-sink v0.3.28 [INFO] [stderr] Compiling heck v0.4.1 [INFO] [stderr] Compiling rustix v0.37.19 [INFO] [stderr] Compiling futures-channel v0.3.28 [INFO] [stderr] Compiling futures-task v0.3.28 [INFO] [stderr] Compiling either v1.8.1 [INFO] [stderr] Compiling smallvec v1.10.0 [INFO] [stderr] Compiling aho-corasick v1.0.1 [INFO] [stderr] Compiling memoffset v0.8.0 [INFO] [stderr] Compiling regex-syntax v0.7.1 [INFO] [stderr] Compiling lock_api v0.4.9 [INFO] [stderr] Checking scopeguard v1.2.0 [INFO] [stderr] Compiling version_check v0.9.4 [INFO] [stderr] Compiling target-lexicon v0.12.7 [INFO] [stderr] Compiling parking_lot_core v0.9.7 [INFO] [stderr] Compiling num-traits v0.2.15 [INFO] [stderr] Compiling glob v0.3.1 [INFO] [stderr] Compiling anyhow v1.0.71 [INFO] [stderr] Compiling syn v2.0.15 [INFO] [stderr] Compiling crossbeam-epoch v0.9.14 [INFO] [stderr] Compiling lazy_static v1.4.0 [INFO] [stderr] Compiling version-compare v0.1.1 [INFO] [stderr] Compiling jobserver v0.1.26 [INFO] [stderr] Compiling which v4.4.0 [INFO] [stderr] Compiling atty v0.2.14 [INFO] [stderr] Compiling cc v1.0.79 [INFO] [stderr] Compiling clang-sys v1.6.1 [INFO] [stderr] Compiling linux-raw-sys v0.3.7 [INFO] [stderr] Compiling tokio v1.28.1 [INFO] [stderr] Compiling termcolor v1.2.0 [INFO] [stderr] Checking getrandom v0.2.9 [INFO] [stderr] Checking num_cpus v1.15.0 [INFO] [stderr] Compiling minimal-lexical v0.2.1 [INFO] [stderr] Compiling cfg-expr v0.15.1 [INFO] [stderr] Checking socket2 v0.4.9 [INFO] [stderr] Compiling nom v7.1.3 [INFO] [stderr] Compiling libloading v0.7.4 [INFO] [stderr] Compiling memoffset v0.6.5 [INFO] [stderr] Compiling rayon-core v1.11.0 [INFO] [stderr] Compiling num-integer v0.1.45 [INFO] [stderr] Compiling rustc-hash v1.1.0 [INFO] [stderr] Compiling peeking_take_while v0.1.2 [INFO] [stderr] Compiling shlex v1.1.0 [INFO] [stderr] Compiling lazycell v1.3.0 [INFO] [stderr] Compiling humantime v2.1.0 [INFO] [stderr] Checking adler v1.0.2 [INFO] [stderr] Compiling unicode-width v0.1.10 [INFO] [stderr] Checking crossbeam-channel v0.5.8 [INFO] [stderr] Compiling textwrap v0.11.0 [INFO] [stderr] Compiling strsim v0.8.0 [INFO] [stderr] Compiling bindgen v0.59.2 [INFO] [stderr] Compiling ansi_term v0.12.1 [INFO] [stderr] Compiling unicode-segmentation v1.10.1 [INFO] [stderr] Compiling vec_map v0.8.2 [INFO] [stderr] Checking parking_lot v0.12.1 [INFO] [stderr] Checking signal-hook-registry v1.4.1 [INFO] [stderr] Compiling regex v1.8.1 [INFO] [stderr] Compiling zstd-sys v2.0.8+zstd.1.5.5 [INFO] [stderr] Checking tracing-core v0.1.30 [INFO] [stderr] Checking rand_core v0.6.4 [INFO] [stderr] Checking mio v0.8.6 [INFO] [stderr] Compiling fastrand v1.9.0 [INFO] [stderr] Compiling clap v2.34.0 [INFO] [stderr] Compiling proc-macro2 v0.4.30 [INFO] [stderr] Compiling protobuf v3.2.0 [INFO] [stderr] Compiling heck v0.3.3 [INFO] [stderr] Compiling same-file v1.0.6 [INFO] [stderr] Compiling strum v0.18.0 [INFO] [stderr] Compiling walkdir v2.3.3 [INFO] [stderr] Compiling unicode-xid v0.1.0 [INFO] [stderr] Compiling version-compare v0.0.10 [INFO] [stderr] Checking crossbeam-deque v0.8.3 [INFO] [stderr] Compiling crossbeam-queue v0.3.8 [INFO] [stderr] Checking itoa v1.0.6 [INFO] [stderr] Compiling syn v0.15.44 [INFO] [stderr] Compiling cexpr v0.6.0 [INFO] [stderr] Compiling zstd-safe v6.0.5+zstd.1.5.4 [INFO] [stderr] Compiling libsodium-sys v0.2.7 [INFO] [stderr] Compiling env_logger v0.9.3 [INFO] [stderr] Compiling quote v0.6.13 [INFO] [stderr] Checking ppv-lite86 v0.2.17 [INFO] [stderr] Compiling backtrace v0.3.67 [INFO] [stderr] Checking rayon v1.7.0 [INFO] [stderr] Checking rand_chacha v0.3.1 [INFO] [stderr] Compiling tempfile v3.5.0 [INFO] [stderr] Checking rand v0.8.5 [INFO] [stderr] Checking miniz_oxide v0.6.2 [INFO] [stderr] Checking is-terminal v0.4.7 [INFO] [stderr] Checking dirs-sys-next v0.1.2 [INFO] [stderr] Compiling proc-macro-error-attr v1.0.4 [INFO] [stderr] Compiling proc-macro-error v1.0.4 [INFO] [stderr] Compiling serde_json v1.0.96 [INFO] [stderr] Checking ryu v1.0.13 [INFO] [stderr] Checking nix v0.23.2 [INFO] [stderr] Checking time v0.1.45 [INFO] [stderr] Checking overload v0.1.1 [INFO] [stderr] Checking iana-time-zone v0.1.56 [INFO] [stderr] Checking signature v1.6.4 [INFO] [stderr] Checking gimli v0.27.2 [INFO] [stderr] Checking chrono v0.4.24 [INFO] [stderr] Checking ed25519 v1.5.3 [INFO] [stderr] Checking nu-ansi-term v0.46.0 [INFO] [stderr] Checking dirs-next v2.0.0 [INFO] [stderr] error: could not compile `syn` (lib) [INFO] [stderr] [INFO] [stderr] Caused by: [INFO] [stderr] process didn't exit successfully: `/opt/rustwide/rustup-home/toolchains/d614ed876e31a5f3ad1d0fbf848fcdab3a29d1d8/bin/rustc --crate-name syn --edition=2018 /opt/rustwide/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/syn-1.0.109/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no --cfg 'feature="clone-impls"' --cfg 'feature="default"' --cfg 'feature="derive"' --cfg 'feature="extra-traits"' --cfg 'feature="fold"' --cfg 'feature="full"' --cfg 'feature="parsing"' --cfg 'feature="printing"' --cfg 'feature="proc-macro"' --cfg 'feature="quote"' --cfg 'feature="visit"' --cfg 'feature="visit-mut"' -C metadata=657ee4e70bbd71a6 -C extra-filename=-657ee4e70bbd71a6 --out-dir /opt/rustwide/target/debug/deps -L dependency=/opt/rustwide/target/debug/deps --extern proc_macro2=/opt/rustwide/target/debug/deps/libproc_macro2-903f180e75a7b179.rmeta --extern quote=/opt/rustwide/target/debug/deps/libquote-7a02cec12c898183.rmeta --extern unicode_ident=/opt/rustwide/target/debug/deps/libunicode_ident-25d7c174b9af81f4.rmeta --cap-lints allow --cap-lints=forbid` (signal: 9, SIGKILL: kill) [INFO] [stderr] warning: build failed, waiting for other jobs to finish... [INFO] running `Command { std: "docker" "inspect" "4445f0defc1fa97159ebe85f4ef170034c5e9435cc552c304b51513c53706fbb", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "4445f0defc1fa97159ebe85f4ef170034c5e9435cc552c304b51513c53706fbb", kill_on_drop: false }` [INFO] [stdout] 4445f0defc1fa97159ebe85f4ef170034c5e9435cc552c304b51513c53706fbb