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solana-with-rpc-optimizations
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Add #[repr(C)] for more future-proof byte mangling (#33085) 

* Add #[repr(C)] for more future-proof byte manglng

* Improve comments after code-review
This commit is contained in:
Ryo Onodera 2023-08-31 22:48:24 +09:00 committed by GitHub
parent 025651e0d4
commit 92a0b310c1
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1 changed files with 17 additions and 10 deletions
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27
accounts-db/src/accounts_db.rs
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@ -12561,13 +12561,16 @@ pub mod tests {
#[test]
fn test_hash_stored_account() {
// This test uses some UNSAFE tricks to detect most of account's field
// addition and deletion without changing the hash code
// This test uses some UNSAFE tricks to detect most of hashing code changes, resulting from
// account's field additions and deletions of StoredAccountMeta and AccountSharedData and
// hashing-order changes.
const ACCOUNT_DATA_LEN: usize = 3;
// the type of InputTuple elements must not contain references;
// the type of InputFields elements must not contain references;
// they should be simple scalars or data blobs
type InputTuple = (
// repr(C) is needed for abi-stability in the dirtiest variant of std::mem::transmute().
#[repr(C)]
struct InputFields(
Slot,
StoredMeta,
AccountMeta,
@ -12575,19 +12578,23 @@ pub mod tests {
usize, // for StoredAccountMeta::offset
Hash,
);
const INPUT_LEN: usize = std::mem::size_of::<InputTuple>();
const INPUT_LEN: usize = std::mem::size_of::<InputFields>();
type InputBlob = [u8; INPUT_LEN];
let mut blob: InputBlob = [0u8; INPUT_LEN];
// spray memory with decreasing counts so that, data layout can be detected.
// spray memory with decreasing integers so that, data layout change and/or hashing
// reordering can be detected. note that just zeroed blob can't detect field reordering.
for (i, byte) in blob.iter_mut().enumerate() {
*byte = (INPUT_LEN - i) as u8;
}
//UNSAFE: forcibly cast the special byte pattern to actual account fields.
let (slot, meta, account_meta, data, offset, hash): InputTuple =
unsafe { std::mem::transmute::<InputBlob, InputTuple>(blob) };
let InputFields(slot, meta, account_meta, data, offset, hash) =
unsafe { std::mem::transmute::<InputBlob, InputFields>(blob) };
// When adding a field to the following constructor, make sure this is sourced from
// InputFields as well after adding new corresponding one to it. Needless to say, but note
// that the hashing code itself must be adjusted
let stored_account = StoredAccountMeta::AppendVec(AppendVecStoredAccountMeta {
meta: &meta,
account_meta: &account_meta,
@ -12599,9 +12606,9 @@ pub mod tests {
let account = stored_account.to_account_shared_data();
let expected_account_hash = if cfg!(debug_assertions) {
Hash::from_str("6qtBXmRrLdTdAV5bK6bZZJxQA4fPSUBxzQGq2BQSat25").unwrap()
Hash::from_str("8GiQSN2VvWASKPUuZgFkH4v66ihEanrDVXAkMFvLwEa8").unwrap()
} else {
Hash::from_str("5HL9MtsQmxZQ8XSgcAhSkqnrayQFXUY8FT1JsHjDNKbi").unwrap()
Hash::from_str("9MYASra3mm8oXzMapYUonB6TcRsKFPtjhNXVgY3MPPUX").unwrap()
};
assert_eq!(