{"id":"ca75b6fdc2c06260","repo":"rust-lang/cargo","slug":"no-argv-0","errorCode":null,"errorMessage":"no argv[0]","messagePattern":"no argv\\[0\\]","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/context/mod.rs","lineNumber":587,"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":569,"sourceCodeEnd":605,"githubUrl":"https://github.com/rust-lang/cargo/blob/0e07a155371a6ce88ae53a2c00df940280c09a67/src/context/mod.rs#L569-L605","documentation":"As the last resort in cargo_exe, from_argv (mod.rs:577-589) reads env::args_os().next() to get argv[0]. If that iterator yields no value at all (no program name), it bails 'no argv[0]'. This is extraordinarily rare since a process normally always has argv[0].","triggerScenarios":"The process was started with a zero-length argv (e.g. via execve with an empty argv array) AND current_exe() failed AND $CARGO is unset, so the argv[0] fallback is reached and finds nothing.","commonSituations":"Exotic launchers that exec with empty argv; corrupted/odd process spawning in sandbox or fuzz harness; OS where current_exe is unavailable (no /proc) combined with empty argv.","solutions":["Launch the process with a proper argv[0] (the program name).","Set `CARGO` env var so the argv fallback is never needed.","Ensure /proc is mounted so current_exe() succeeds first."],"exampleFix":"# before (execve with empty argv)\nexecve(\"/usr/bin/cargo\", [], envp)   # no argv[0]\n# after\nexecve(\"/usr/bin/cargo\", [\"cargo\", \"build\"], envp)","handlingStrategy":"validation","validationCode":"# Never exec a process with empty argv; always include argv[0]:\nexecve(\"/usr/bin/cargo\", [\"cargo\", \"build\"], envp)","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Always pass a real argv[0] when spawning processes.","Set CARGO so the argv[0] fallback path is never needed.","Mount /proc so current_exe() resolves first."],"tags":["environment","cargo-exe","argv","process"],"analyzedSha":"0e07a155371a6ce88ae53a2c00df940280c09a67","analyzedAt":"2026-08-06T01:46:58.334Z","schemaVersion":2}