2cde8d967a
When PR #147572 switched WASI to use Unix-style filesystem APIs, the open_to_and_set_permissions function for WASI was implemented to call OpenOptions::new().open() without setting any access mode flags. This causes std::fs::copy to fail with the error: "must specify at least one of read, write, or append access" The fix is to explicitly set .write(true), .create(true), and .truncate(true) on the OpenOptions, matching the behavior of the non-WASI Unix implementation but without the permission handling that WASI doesn't support. Minimal reproduction: fn main() { std::fs::write("/src.txt", b"test").unwrap(); match std::fs::copy("/src.txt", "/dst.txt") { Ok(_) => println!("PASS: fs::copy works!"), Err(e) => println!("FAIL: {}", e), } } # Compile and run: rustc +nightly --target wasm32-wasip2 test.rs -o test.wasm wasmtime -S cli --dir . test.wasm # Before fix: FAIL: must specify at least one of read, write, or append access # After fix: PASS: fs::copy works! Note: The existing test library/std/src/fs/tests.rs::copy_file_ok would have caught this regression if the std test suite ran on WASI targets. Currently std tests don't compile for wasm32-wasip2 due to Unix-specific test code in library/std/src/sys/fd/unix/tests.rs. Fixes the regression introduced in nightly-2025-12-10. |
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This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Why Rust?
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