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commit 618d64c2e0c3faa1acc5bf2cd2c7b7fa73b479e9
Author: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri Jan 26 10:49:17 2024 +1100
Fix `proc macro panicked` with `Invalid type` in `const_random!` in Rust 1.77.
With Rust nightly 1.77, any invocation of `const_random!` with a `u8`
array causes a compile-time panic. This can be seen when running `cargo
test`:
```
error: proc macro panicked
--> tests/tests.rs:52:28
|
52 | const VALUE1: &[u8] = &const_random!([u8; 30]);
| ^^^^^^^^^^^^^^^^^^^^^^^
|
= help: message: Invalid type
```
This is because the proc macro starts by calling `to_string` on the
input token stream, and then uses substring matching to "parse" it. In
Rust 1.77 the `Display` impl for `TokenStream` has changed, and what
used to be converted to the string `"[u8 ; 30]"` is now `"[u8; 30]"`. As
a result, the `byte_array.starts_with("[u8 ; ")` call fails.
Note that substring matching is inherently flawed because the whitespace
in the output of `to_string` is not guaranteed.
This commit rewrites the proc macro to be robust in the face of
`to_string` whitespace changes, by iterating over the individual
`TokenTrees`s.
The commit also adds a comment explaining why `usize` and `isize` are
handled differently, because it's subtle.
Note: I ran `cargo fmt` within `macro/` to format the changes to
`macro/src/lib.rs` and it made some minor changes to `macro/src/span.rs`
as well.
diff --git macro/src/lib.rs macro/src/lib.rs
index f65695631..732028394 100644
--- macro/src/lib.rs
+++ macro/src/lib.rs
@@ -1,11 +1,9 @@
-#[allow(unused_extern_crates)]
extern crate proc_macro;
use proc_macro::*;
use std::iter::once;
mod span;
-use crate::span::{gen_random_bytes, gen_random};
-
+use crate::span::{gen_random, gen_random_bytes};
/// Create a TokenStream of an identifier out of a string
fn ident(ident: &str) -> TokenStream {
@@ -14,44 +12,89 @@ fn ident(ident: &str) -> TokenStream {
#[proc_macro]
pub fn const_random(input: TokenStream) -> TokenStream {
- match &input.to_string()[..] {
- "u8" => TokenTree::from(Literal::u8_suffixed(gen_random())).into(),
- "u16" => TokenTree::from(Literal::u16_suffixed(gen_random())).into(),
- "u32" => TokenTree::from(Literal::u32_suffixed(gen_random())).into(),
- "u64" => TokenTree::from(Literal::u64_suffixed(gen_random())).into(),
- "u128" => TokenTree::from(Literal::u128_suffixed(gen_random())).into(),
- "i8" => TokenTree::from(Literal::i8_suffixed(gen_random())).into(),
- "i16" => TokenTree::from(Literal::i16_suffixed(gen_random())).into(),
- "i32" => TokenTree::from(Literal::i32_suffixed(gen_random())).into(),
- "i64" => TokenTree::from(Literal::i64_suffixed(gen_random())).into(),
- "i128" => TokenTree::from(Literal::i128_suffixed(gen_random())).into(),
- "usize" => {
- let value: TokenStream = TokenTree::from(Literal::u128_suffixed(gen_random())).into();
- let type_cast: TokenStream = [value, ident("as"), ident("usize")]
- .iter()
- .cloned()
- .collect();
- TokenTree::from(Group::new(Delimiter::Parenthesis, type_cast)).into()
+ let mut iter = input.into_iter();
+ let Some(tt) = iter.next() else {
+ panic!("missing type arg");
+ };
+
+ let result = match &tt {
+ TokenTree::Ident(id) => {
+ let s = id.to_string();
+ match s.as_str() {
+ "u8" => TokenTree::from(Literal::u8_suffixed(gen_random())).into(),
+ "u16" => TokenTree::from(Literal::u16_suffixed(gen_random())).into(),
+ "u32" => TokenTree::from(Literal::u32_suffixed(gen_random())).into(),
+ "u64" => TokenTree::from(Literal::u64_suffixed(gen_random())).into(),
+ "u128" => TokenTree::from(Literal::u128_suffixed(gen_random())).into(),
+ "i8" => TokenTree::from(Literal::i8_suffixed(gen_random())).into(),
+ "i16" => TokenTree::from(Literal::i16_suffixed(gen_random())).into(),
+ "i32" => TokenTree::from(Literal::i32_suffixed(gen_random())).into(),
+ "i64" => TokenTree::from(Literal::i64_suffixed(gen_random())).into(),
+ "i128" => TokenTree::from(Literal::i128_suffixed(gen_random())).into(),
+ "usize" => {
+ // Note: usize does not implement `Random` and follow the pattern above. If it
+ // did, when cross-compiling from a 32-bit host to a 64-bit target,
+ // `usize::random()` would produce a 32-bit random usize which would then be
+ // turned into a suffixed literal (e.g. `0x1234_5678usize`). On the 64-bit
+ // target that literal would always have the upper 32 bits as zero, which would
+ // be bad. Instead we produce code that will generate a 128-bit integer literal
+ // (on the host) and then truncate it to usize (on the target).
+ let value: TokenStream =
+ TokenTree::from(Literal::u128_suffixed(gen_random())).into();
+ let type_cast: TokenStream = [value, ident("as"), ident("usize")]
+ .iter()
+ .cloned()
+ .collect();
+ TokenTree::from(Group::new(Delimiter::Parenthesis, type_cast)).into()
+ }
+ "isize" => {
+ // The same reasoning as `usize` applies for `isize`.
+ let value: TokenStream =
+ TokenTree::from(Literal::i128_suffixed(gen_random())).into();
+ let type_cast: TokenStream = [value, ident("as"), ident("isize")]
+ .iter()
+ .cloned()
+ .collect();
+ TokenTree::from(Group::new(Delimiter::Parenthesis, type_cast)).into()
+ }
+ _ => panic!("invalid integer type arg: `{}`", s),
+ }
}
- "isize" => {
- let value: TokenStream = TokenTree::from(Literal::i128_suffixed(gen_random())).into();
- let type_cast: TokenStream = [value, ident("as"), ident("isize")]
- .iter()
- .cloned()
- .collect();
- TokenTree::from(Group::new(Delimiter::Parenthesis, type_cast)).into()
+ TokenTree::Group(group) if group.delimiter() == Delimiter::Bracket => {
+ let mut iter = group.stream().into_iter();
+ match (&iter.next(), &iter.next(), &iter.next(), &iter.next()) {
+ (
+ Some(TokenTree::Ident(ident)),
+ Some(TokenTree::Punct(punct)),
+ Some(TokenTree::Literal(literal)),
+ None,
+ ) if ident.to_string().as_str() == "u8" && punct.as_char() == ';' => {
+ let Ok(len) = literal.to_string().parse() else {
+ panic!("invalid array length: `{}`", literal);
+ };
+ let mut random_bytes = vec![0; len];
+ gen_random_bytes(&mut random_bytes);
+ let array_parts: TokenStream = random_bytes
+ .into_iter()
+ .flat_map(|byte| {
+ let val = TokenTree::from(Literal::u8_suffixed(byte));
+ let comma = TokenTree::from(Punct::new(',', Spacing::Alone));
+ once(val).chain(once(comma))
+ })
+ .collect();
+ TokenTree::from(Group::new(Delimiter::Bracket, array_parts)).into()
+ }
+ _ => panic!("invalid array type arg: `{}`", tt),
+ }
}
- byte_array if byte_array.starts_with("[u8 ; ") && byte_array.ends_with(']')=> {
- let len = byte_array[6..byte_array.len()-1].parse().unwrap();
- let mut random_bytes = vec![0; len];
- gen_random_bytes(&mut random_bytes);
- let array_parts: TokenStream = random_bytes.into_iter().flat_map(|byte| {
- let val = TokenTree::from(Literal::u8_suffixed(byte));
- let comma = TokenTree::from(Punct::new(',', Spacing::Alone));
- once(val).chain(once(comma))
- }).collect();
- TokenTree::from(Group::new(Delimiter::Bracket, array_parts)).into()
+ _ => {
+ panic!("invalid type arg: `{}`", tt);
}
- _ => panic!("Invalid type"),
- }
+ };
+
+ if let Some(tt) = iter.next() {
+ panic!("invalid trailing token tree: `{}`", tt);
+ };
+
+ result
}
diff --git macro/src/span.rs macro/src/span.rs
index ab72bb08e..e9bda8d69 100644
--- macro/src/span.rs
+++ macro/src/span.rs
@@ -2,16 +2,15 @@ use proc_macro::Span;
use std::option_env;
use once_cell::race::OnceBox;
-use tiny_keccak::{Xof, Hasher, Shake};
-
+use tiny_keccak::{Hasher, Shake, Xof};
static SEED: OnceBox<Vec<u8>> = OnceBox::new();
fn get_seed() -> &'static [u8] {
&SEED.get_or_init(|| {
if let Some(value) = option_env!("CONST_RANDOM_SEED") {
- Box::new(value.as_bytes().to_vec())
- } else {
+ Box::new(value.as_bytes().to_vec())
+ } else {
let mut value = [0u8; 32];
getrandom::getrandom(&mut value).unwrap();
Box::new(value.to_vec())
|
