{"record":{"id":"ca75b6fdc2c06260","repo":"rust-lang/cargo","slug":"no-argv-0","errorCode":null,"errorMessage":"no argv[0]","messagePattern":"no argv\\[0\\]","errorType":"exception","errorClass":"anyhow::Error","httpStatus":null,"severity":"error","filePath":"src/context/mod.rs","lineNumber":583,"sourceCode":"                    // Try fetching the path to `cargo` using `env::current_exe()`.\n                    // The method varies per operating system and might fail; in particular,\n                    // it depends on `/proc` being mounted on Linux, and some environments\n                    // (like containers or chroots) may not have that available.\n                    let exe = env::current_exe()?;\n                    Ok(exe)\n                }\n\n                fn from_argv() -> CargoResult<PathBuf> {\n                    // Grab `argv[0]` and attempt to resolve it to an absolute path.\n                    // If `argv[0]` has one component, it must have come from a `PATH` lookup,\n                    // so probe `PATH` in that case.\n                    // Otherwise, it has multiple components and is either:\n                    // - a relative path (e.g., `./cargo`, `target/debug/cargo`), or\n                    // - an absolute path (e.g., `/usr/local/bin/cargo`).\n                    let argv0 = env::args_os()\n                        .map(PathBuf::from)\n                        .next()\n                        .ok_or_else(|| anyhow!(\"no argv[0]\"))?;\n                    paths::resolve_executable(&argv0)\n                }\n\n                // Determines whether `path` is a cargo binary.\n                // See: https://github.com/rust-lang/cargo/issues/15099#issuecomment-2666737150\n                fn is_cargo(path: &Path) -> bool {\n                    path.file_stem() == Some(OsStr::new(\"cargo\"))\n                }\n\n                let from_current_exe = from_current_exe();\n                if from_current_exe.as_deref().is_ok_and(is_cargo) {\n                    return from_current_exe;\n                }\n\n                let from_argv = from_argv();\n                if from_argv.as_deref().is_ok_and(is_cargo) {\n                    return from_argv;\n                }","sourceCodeStart":565,"sourceCodeEnd":601,"githubUrl":"https://github.com/rust-lang/cargo/blob/98a09e7e7d62850f14e5b6132101fc1edd19a16f/src/context/mod.rs#L565-L601","documentation":"Thrown by the from_argv() helper inside cargo_exe() when env::args_os() yields no elements at all — the process was started without even an argv[0]. This is the third and last-resort fallback in Cargo's binary-detection chain, reached only when both $CARGO and env::current_exe() did not yield a valid cargo path.","triggerScenarios":"Process launched with a completely empty argument vector (no argv[0]), which is theoretically possible via direct execve with a zero-length argv array but extremely rare in practice.","commonSituations":"Custom process spawners that call execve with an empty argv. Debugging tools or sandboxing layers that strip argv. Essentially never encountered in normal CLI usage.","solutions":["Ensure the process is launched with at least argv[0] set to the executable path or name","Set the CARGO environment variable so the from_env fallback succeeds before from_argv is reached","Ensure /proc is mounted so env::current_exe() resolves before from_argv is reached"],"exampleFix":null,"handlingStrategy":"validation","validationCode":"// Ensure argv[0] exists before relying on cargo_exe()\nfn ensure_argv0() -> Result<(), anyhow::Error> {\n    if std::env::args_os().next().is_none() {\n        anyhow::bail!(\"process started without argv[0]; cannot locate cargo\");\n    }\n    Ok(())\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Ensure the process is always launched with a valid argv[0] via standard exec","Set CARGO env var so from_env() succeeds before from_argv() is ever reached","This error is nearly impossible to trigger in normal CLI usage — investigate process spawning code if encountered"],"tags":["environment","cargo-binary","process"],"backgroundTag":null,"analyzedSha":"98a09e7e7d62850f14e5b6132101fc1edd19a16f","analyzedAt":"2026-08-11T17:42:36.556Z","contentChangedAt":"2026-08-11T17:42:36.556Z","schemaVersion":2},"datasetVersion":"2026-09-23T08:17:48.524Z"}