1 files changed, 192 insertions, 0 deletions
diff --git a/third_party/rust/wasm-smith/src/lib.rs b/third_party/rust/wasm-smith/src/lib.rs
new file mode 100644
index 0000000000..8d17290473
--- /dev/null
+++ b/third_party/rust/wasm-smith/src/lib.rs
@@ -0,0 +1,192 @@
+//! A WebAssembly test case generator.
+//!
+//! ## Usage
+//!
+//! First, use [`cargo fuzz`](https://github.com/rust-fuzz/cargo-fuzz) to define
+//! a new fuzz target:
+//!
+//! ```shell
+//! $ cargo fuzz add my_wasm_smith_fuzz_target
+//! ```
+//!
+//! Next, add `wasm-smith` to your dependencies:
+//!
+//! ```shell
+//! $ cargo add wasm-smith
+//! ```
+//!
+//! Then, define your fuzz target so that it takes arbitrary
+//! `wasm_smith::Module`s as an argument, convert the module into serialized
+//! Wasm bytes via the `to_bytes` method, and then feed it into your system:
+//!
+//! ```no_run
+//! // fuzz/fuzz_targets/my_wasm_smith_fuzz_target.rs
+//!
+//! #![no_main]
+//!
+//! use libfuzzer_sys::fuzz_target;
+//! use wasm_smith::Module;
+//!
+//! fuzz_target!(|module: Module| {
+//!     let wasm_bytes = module.to_bytes();
+//!
+//!     // Your code here...
+//! });
+//! ```
+//!
+//! Finally, start fuzzing:
+//!
+//! ```shell
+//! $ cargo fuzz run my_wasm_smith_fuzz_target
+//! ```
+//!
+//! > **Note:** For a real world example, also check out [the `validate` fuzz
+//! > target](https://github.com/fitzgen/wasm-smith/blob/main/fuzz/fuzz_targets/validate.rs)
+//! > defined in this repository. Using the `wasmparser` crate, it checks that
+//! > every module generated by `wasm-smith` validates successfully.
+//!
+//! ## Design
+//!
+//! The design and implementation strategy of wasm-smith is outlined in
+//! [this article](https://fitzgeraldnick.com/2020/08/24/writing-a-test-case-generator.html).
+
+#![deny(missing_docs, missing_debug_implementations)]
+// Needed for the `instructions!` macro in `src/code_builder.rs`.
+#![recursion_limit = "512"]
+
+mod component;
+mod config;
+mod core;
+
+pub use crate::core::{InstructionKind, InstructionKinds, MaybeInvalidModule, Module};
+use arbitrary::{Result, Unstructured};
+pub use component::Component;
+pub use config::{Config, MemoryOffsetChoices};
+use std::{collections::HashSet, fmt::Write, str};
+
+#[cfg(feature = "_internal_cli")]
+pub use config::InternalOptionalConfig;
+
+/// Do something an arbitrary number of times.
+///
+/// The callback can return `false` to exit the loop early.
+pub(crate) fn arbitrary_loop<'a>(
+    u: &mut Unstructured<'a>,
+    min: usize,
+    max: usize,
+    mut f: impl FnMut(&mut Unstructured<'a>) -> Result<bool>,
+) -> Result<()> {
+    assert!(max >= min);
+    for _ in 0..min {
+        if !f(u)? {
+            return Err(arbitrary::Error::IncorrectFormat);
+        }
+    }
+    for _ in 0..(max - min) {
+        let keep_going = u.arbitrary().unwrap_or(false);
+        if !keep_going {
+            break;
+        }
+
+        if !f(u)? {
+            break;
+        }
+    }
+
+    Ok(())
+}
+
+// Mirror what happens in `Arbitrary for String`, but do so with a clamped size.
+pub(crate) fn limited_str<'a>(max_size: usize, u: &mut Unstructured<'a>) -> Result<&'a str> {
+    let size = u.arbitrary_len::<u8>()?;
+    let size = std::cmp::min(size, max_size);
+    match str::from_utf8(u.peek_bytes(size).unwrap()) {
+        Ok(s) => {
+            u.bytes(size).unwrap();
+            Ok(s)
+        }
+        Err(e) => {
+            let i = e.valid_up_to();
+            let valid = u.bytes(i).unwrap();
+            let s = unsafe {
+                debug_assert!(str::from_utf8(valid).is_ok());
+                str::from_utf8_unchecked(valid)
+            };
+            Ok(s)
+        }
+    }
+}
+
+pub(crate) fn limited_string(max_size: usize, u: &mut Unstructured) -> Result<String> {
+    Ok(limited_str(max_size, u)?.into())
+}
+
+pub(crate) fn unique_string(
+    max_size: usize,
+    names: &mut HashSet<String>,
+    u: &mut Unstructured,
+) -> Result<String> {
+    let mut name = limited_string(max_size, u)?;
+    while names.contains(&name) {
+        write!(&mut name, "{}", names.len()).unwrap();
+    }
+    names.insert(name.clone());
+    Ok(name)
+}
+
+pub(crate) fn unique_kebab_string(
+    max_size: usize,
+    names: &mut HashSet<String>,
+    u: &mut Unstructured,
+) -> Result<String> {
+    let size = std::cmp::min(u.arbitrary_len::<u8>()?, max_size);
+    let mut name = String::with_capacity(size);
+    let mut require_alpha = true;
+    for _ in 0..size {
+        name.push(match u.int_in_range::<u8>(0..=36)? {
+            x if (0..26).contains(&x) => {
+                require_alpha = false;
+                (b'a' + x) as char
+            }
+            x if (26..36).contains(&x) => {
+                if require_alpha {
+                    require_alpha = false;
+                    (b'a' + (x - 26)) as char
+                } else {
+                    (b'0' + (x - 26)) as char
+                }
+            }
+            x if x == 36 => {
+                if require_alpha {
+                    require_alpha = false;
+                    'a'
+                } else {
+                    require_alpha = true;
+                    '-'
+                }
+            }
+            _ => unreachable!(),
+        });
+    }
+
+    if name.is_empty() || name.ends_with('-') {
+        name.push('a');
+    }
+
+    while names.contains(&name) {
+        write!(&mut name, "{}", names.len()).unwrap();
+    }
+
+    names.insert(name.clone());
+
+    Ok(name)
+}
+
+pub(crate) fn unique_url(
+    max_size: usize,
+    names: &mut HashSet<String>,
+    u: &mut Unstructured,
+) -> Result<String> {
+    let path = unique_kebab_string(max_size, names, u)?;
+    Ok(format!("https://example.com/{path}"))
+}