This should avoid the remaining non-determistic code coverage paths.
Without this patch, the tool would report a diff (only when running
without libFuzzer):
cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32
It should be sufficient to set it once. Especially, if the dynamic value
is only used by ResetAndInitialize.
This also avoids non-determistic code paths, when ResetAndInitialize may
re-initialize m_next_inv_to_inbounds.
Without this patch, the tool would report a diff:
cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32
...
- 1126| 3| m_next_inv_to_inbounds = now + m_rng.rand_exp_duration(average_interval);
- 1127| 3| }
+ 1126| 10| m_next_inv_to_inbounds = now + m_rng.rand_exp_duration(average_interval);
+ 1127| 10| }
1128| 491| return m_next_inv_to_inbounds;
...
This allows the clock to be mockable in tests. Also, replace cs_main
with GetMutex() while touching this function.
Also, use the ElapseSteady test helper in the p2p_headers_presync fuzz
target to make it more deterministic.
The m_last_presync_update variable is a global that is not reset in
ResetAndInitialize. However, it is only used for logging, so completely
disable it for now.
Without this patch, the tool would report a diff:
cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32
...
4468| 81| auto now = std::chrono::steady_clock::now();
4469| 81| if (now < m_last_presync_update + std::chrono::milliseconds{250}) return;
- ^80
+ ^79
...
The global m_headers_presync_stats is not reset in ResetAndInitialize.
This may lead to non-determinism.
Fix it by incrementing the global node id counter instead.
Without this patch, the tool would report a diff:
cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32
...
2587| 3.73k| if (best_it == m_headers_presync_stats.end()) {
------------------
- | Branch (2587:17): [True: 80, False: 3.65k]
+ | Branch (2587:17): [True: 73, False: 3.66k]
------------------
...
The hardcoded nBits range would occasionally produce values for
the difficulty target that were too low, causing the total work
of the test chain to exceed MinimumChainWork. This fix uses
ConsumeArithUInt256InRange to properly generate targets that
will produce header chains with less work than MinimumChainWork.
