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Enable memory sanitizer tests again #435

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Merged
fitzgen merged 1 commit into from
Jan 27, 2026
Merged

Enable memory sanitizer tests again #435

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156 changes: 77 additions & 79 deletions tests/tests/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -437,85 +437,83 @@ fn run_without_sanitizer_with_crash() {
.failure();
}

// TODO: these msan tests are crashing `rustc` in CI:
// https://github.com/rust-fuzz/cargo-fuzz/issues/323
//
// #[test]
// fn run_with_msan_no_crash() {
// let project = project("run_with_msan_no_crash")
// .with_fuzz()
// .fuzz_target(
// "msan_no_crash",
// r#"
// #![no_main]
// use libfuzzer_sys::fuzz_target;
//
// fuzz_target!(|data: &[u8]| {
// // get data from fuzzer and print it
// // to force a memory access that cannot be optimized out
// if let Some(x) = data.get(0) {
// dbg!(x);
// }
// });
// "#,
// )
// .build();
//
// project
// .cargo_fuzz()
// .arg("run")
// .arg("--sanitizer=memory")
// .arg("msan_no_crash")
// .arg("--")
// .arg("-runs=1000")
// .assert()
// .stderr(predicate::str::contains("Done 1000 runs"))
// .success();
// }
//
// #[test]
// fn run_with_msan_with_crash() {
// let project = project("run_with_msan_with_crash")
// .with_fuzz()
// .fuzz_target(
// "msan_with_crash",
// r#"
// #![no_main]
// use libfuzzer_sys::fuzz_target;
//
// fuzz_target!(|data: &[u8]| {
// let test_data: Vec<u8> = Vec::with_capacity(4);
// let uninitialized_value = unsafe {test_data.get_unchecked(0)};
// // prevent uninit read from being optimized out
// println!("{}", uninitialized_value);
// });
// "#,
// )
// .build();
//
// project
// .cargo_fuzz()
// .arg("run")
// .arg("--sanitizer=memory")
// .arg("msan_with_crash")
// .arg("--")
// .arg("-runs=1000")
// .assert()
// .stderr(
// predicate::str::contains("MemorySanitizer: use-of-uninitialized-value")
// .and(predicate::str::contains(
// "Reproduce with:\n\
// \n\
// \tcargo fuzz run --sanitizer=memory msan_with_crash fuzz/artifacts/msan_with_crash/crash-",
// ))
// .and(predicate::str::contains(
// "Minimize test case with:\n\
// \n\
// \tcargo fuzz tmin --sanitizer=memory msan_with_crash fuzz/artifacts/msan_with_crash/crash-",
// )),
// )
// .failure();
// }
#[test]
fn run_with_msan_no_crash() {
let project = project("run_with_msan_no_crash")
.with_fuzz()
.fuzz_target(
"msan_no_crash",
r#"
#![no_main]
use libfuzzer_sys::fuzz_target;
use std::hint::black_box;

fuzz_target!(|data: &[u8]| {
if let Some(x) = data.get(0) {
black_box(x);

@Marcono1234 Marcono1234 Jan 20, 2026

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Have replaced the dbg!(x) here with black_box(x).

Is not strictly needed to enable the tests, but I think black_box should achieve the same goal here and might introduce less overhead than dbg!?

@Marcono1234 Marcono1234 Jan 20, 2026

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Hmm, maybe using black_box is actually a bad idea? See #436

}
});
"#,
)
.build();

project
.cargo_fuzz()
.arg("run")
.arg("--sanitizer=memory")
.arg("msan_no_crash")
.arg("--")
.arg("-runs=1000")
.assert()
.stderr(predicate::str::contains("Done 1000 runs"))
.success();
}

#[test]
fn run_with_msan_with_crash() {
let project = project("run_with_msan_with_crash")
.with_fuzz()
.fuzz_target(
"msan_with_crash",
r#"
#![no_main]
use libfuzzer_sys::fuzz_target;
use std::mem::MaybeUninit;

fuzz_target!(|data: &[u8]| {
unsafe {
let a = MaybeUninit::<[usize; 4]>::uninit();
let a = a.assume_init();
println!("{}", a[2]);
}
});
"#,
)
.build();

project
.cargo_fuzz()
.arg("run")
.arg("--sanitizer=memory")
.arg("msan_with_crash")
.arg("--")
.arg("-runs=1000")
.assert()
.stderr(
predicate::str::contains("MemorySanitizer: use-of-uninitialized-value")
.and(predicate::str::contains(
"Reproduce with:\n\
\n\
\tcargo fuzz run --sanitizer=memory msan_with_crash fuzz/artifacts/msan_with_crash/crash-",
))
.and(predicate::str::contains(
"Minimize test case with:\n\
\n\
\tcargo fuzz tmin --sanitizer=memory msan_with_crash fuzz/artifacts/msan_with_crash/crash-",
)),
)
.failure();
}

#[test]
fn run_one_input() {
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