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Diffstat (limited to 'src/env.rs')
-rw-r--r-- | src/env.rs | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/src/env.rs b/src/env.rs new file mode 100644 index 00000000..0d815be9 --- /dev/null +++ b/src/env.rs @@ -0,0 +1,52 @@ +use {Error, Result}; + +/// Clear the environment of all name-value pairs. +/// +/// On platforms where libc provides `clearenv()`, it will be used. libc's +/// `clearenv()` is documented to return an error code but not set errno; if the +/// return value indicates a failure, this function will return +/// `Error::UnsupportedOperation`. +/// +/// On platforms where libc does not provide `clearenv()`, a fallback +/// implementation will be used that iterates over all environment variables and +/// removes them one-by-one. +/// +/// # Safety +/// +/// This function is not threadsafe and can cause undefined behavior in +/// combination with `std::env` or other program components that access the +/// environment. See, for example, the discussion on `std::env::remove_var`; this +/// function is a case of an "inherently unsafe non-threadsafe API" dealing with +/// the environment. +/// +/// The caller must ensure no other threads access the process environment while +/// this function executes and that no raw pointers to an element of libc's +/// `environ` is currently held. The latter is not an issue if the only other +/// environment access in the program is via `std::env`, but the requirement on +/// thread safety must still be upheld. +pub unsafe fn clearenv() -> Result<()> { + let ret; + cfg_if! { + if #[cfg(any(target_os = "fuchsia", + target_os = "wasi", + target_env = "wasi", + target_env = "uclibc", + target_os = "linux", + target_os = "android", + target_os = "emscripten"))] { + ret = libc::clearenv(); + } else { + use std::env; + for (name, _) in env::vars_os() { + env::remove_var(name); + } + ret = 0; + } + } + + if ret == 0 { + Ok(()) + } else { + Err(Error::UnsupportedOperation) + } +} |