[INFO] cloning repository https://github.com/vi/duplo [INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/vi/duplo" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo", kill_on_drop: false }` [INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo'... [INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }` [INFO] [stdout] 1ad5e27a027a58c572c7c4bdabebfcb527879f46 [INFO] testing vi/duplo against master#1871252fc8bb672d40787e67404e6eaae7059369 for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc1/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc1/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain 1871252fc8bb672d40787e67404e6eaae7059369 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1871252fc8bb672d40787e67404e6eaae7059369" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc1/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+1871252fc8bb672d40787e67404e6eaae7059369" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] [stderr] Updating crates.io index [INFO] [stderr] Downloading crates ... [INFO] [stderr] Downloaded renamore v0.3.2 [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+1871252fc8bb672d40787e67404e6eaae7059369" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 04d51583f3a74c1fc97993fba420db5b2c702ab18f67e11c819e17bf3a44f0c4 [INFO] running `Command { std: "docker" "start" "-a" "04d51583f3a74c1fc97993fba420db5b2c702ab18f67e11c819e17bf3a44f0c4", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "04d51583f3a74c1fc97993fba420db5b2c702ab18f67e11c819e17bf3a44f0c4", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "04d51583f3a74c1fc97993fba420db5b2c702ab18f67e11c819e17bf3a44f0c4", kill_on_drop: false }` [INFO] [stdout] 04d51583f3a74c1fc97993fba420db5b2c702ab18f67e11c819e17bf3a44f0c4 [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+1871252fc8bb672d40787e67404e6eaae7059369" "build" "--frozen" "--message-format=json", kill_on_drop: false }` [INFO] [stdout] cad5a11fe824e89ce753033a7d450c716145c4f33426865c44f28c691ba09316 [INFO] running `Command { std: "docker" "start" "-a" "cad5a11fe824e89ce753033a7d450c716145c4f33426865c44f28c691ba09316", kill_on_drop: false }` [INFO] [stderr] error: failed to create directory `/opt/rustwide/target/debug/.fingerprint/axum-macros-f2f6bd380059e7cc` [INFO] [stderr] [INFO] [stderr] Caused by: [INFO] [stderr] No space left on device (os error 28) [INFO] running `Command { std: "docker" "inspect" "cad5a11fe824e89ce753033a7d450c716145c4f33426865c44f28c691ba09316", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "cad5a11fe824e89ce753033a7d450c716145c4f33426865c44f28c691ba09316", kill_on_drop: false }` [INFO] [stdout] cad5a11fe824e89ce753033a7d450c716145c4f33426865c44f28c691ba09316 [INFO] testing vi/duplo against try#b642703cf9526da1e72c0b6755753b939a9c6b6d for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain b642703cf9526da1e72c0b6755753b939a9c6b6d [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] a4d2bb04408f9488d672ecf1d54b2c2e0abe4f95243dfeb3060b9f673180ca10 [INFO] running `Command { std: "docker" "start" "-a" "a4d2bb04408f9488d672ecf1d54b2c2e0abe4f95243dfeb3060b9f673180ca10", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "a4d2bb04408f9488d672ecf1d54b2c2e0abe4f95243dfeb3060b9f673180ca10", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "a4d2bb04408f9488d672ecf1d54b2c2e0abe4f95243dfeb3060b9f673180ca10", kill_on_drop: false }` [INFO] [stdout] a4d2bb04408f9488d672ecf1d54b2c2e0abe4f95243dfeb3060b9f673180ca10 [INFO] testing vi/duplo against try#b642703cf9526da1e72c0b6755753b939a9c6b6d for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain b642703cf9526da1e72c0b6755753b939a9c6b6d [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 022d99747c382e16c8a41b10ce74ef795503f00dd2937398432fa29cc0d59f2a [INFO] running `Command { std: "docker" "start" "-a" "022d99747c382e16c8a41b10ce74ef795503f00dd2937398432fa29cc0d59f2a", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "022d99747c382e16c8a41b10ce74ef795503f00dd2937398432fa29cc0d59f2a", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "022d99747c382e16c8a41b10ce74ef795503f00dd2937398432fa29cc0d59f2a", kill_on_drop: false }` [INFO] [stdout] 022d99747c382e16c8a41b10ce74ef795503f00dd2937398432fa29cc0d59f2a [INFO] testing vi/duplo against try#b642703cf9526da1e72c0b6755753b939a9c6b6d for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain b642703cf9526da1e72c0b6755753b939a9c6b6d [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 34c5680a558a9200d86f119d3e78f313e01dc82c7375370385e5b77ff5f4f68f [INFO] running `Command { std: "docker" "start" "-a" "34c5680a558a9200d86f119d3e78f313e01dc82c7375370385e5b77ff5f4f68f", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "34c5680a558a9200d86f119d3e78f313e01dc82c7375370385e5b77ff5f4f68f", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "34c5680a558a9200d86f119d3e78f313e01dc82c7375370385e5b77ff5f4f68f", kill_on_drop: false }` [INFO] [stdout] 34c5680a558a9200d86f119d3e78f313e01dc82c7375370385e5b77ff5f4f68f [INFO] testing vi/duplo against try#b642703cf9526da1e72c0b6755753b939a9c6b6d for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain b642703cf9526da1e72c0b6755753b939a9c6b6d [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stderr] Error response from daemon: mkdir /var/lib/docker/overlay2/e733e010957b5371ee3729d61449bbd8e805662af3099a4699d43e7a5132e456/merged/opt/rustwide/workdir: no space left on device [INFO] testing vi/duplo against try#b642703cf9526da1e72c0b6755753b939a9c6b6d for pr-125151 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fvi%2Fduplo" "/workspace/builds/worker-4-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/vi/duplo on toolchain b642703cf9526da1e72c0b6755753b939a9c6b6d [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/vi/duplo [INFO] finished tweaking git repo https://github.com/vi/duplo [INFO] tweaked toml for git repo https://github.com/vi/duplo written to /workspace/builds/worker-4-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/vi/duplo 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" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:59a85a07ab18ca8720692f8e61effa1c651d9e2ca591e072c2b212bb91a6b8b5" "/opt/rustwide/cargo-home/bin/cargo" "+b642703cf9526da1e72c0b6755753b939a9c6b6d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stderr] Error response from daemon: mkdir /var/lib/docker/overlay2/a3dd04c7f08f5ec6b427fe1822df034284602d910fae55e476c480aad85190ab/merged/opt/rustwide: no space left on device [ERROR] this task or one of its parent failed! [ERROR] command failed: exit status: 1 [ERROR] note: run with `RUST_BACKTRACE=1` to display a backtrace.