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v0.16.0 — Fuzz-Driven Stability Release

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@github-actions github-actions released this 19 Apr 12:55
v0.16.0
e0e7653

neo-solidity v0.16.0 + devpack v1.1.0 — Fuzz-Driven Stability Release

Release date: 2026-04-19
Compiler / CLI / workspace: v0.16.0
devpack (@r3e-network/neo-solidity-devpack): v1.1.0

TL;DR

  • ~90 distinct fixes landed through continuous fuzz-harness review
    (Tasks #94–#183), covering arithmetic, ABI encoding, events,
    modifiers, try/catch, yul, storage, and runtime bridging.
  • 409 fuzz harnesses passing (0 failed, 1 ignored) — up from 52 at
    the start of the review cycle.
  • Narrow Yul support lands: mstore/mload/return, let/:=,
    basic arithmetic, and EIP-1153 transient storage (tstore / tload).
  • Checked arithmetic is now canonical: uint256 and int256
    Add/Sub/Mul — plus narrow signed int types — route through BigInt
    with post-op range guards and emit the EVM-canonical
    Panic(uint256) envelope.
  • EVM envelope parity: abi.encode* / abi.decode, event
    topic0 = keccak256(signature), Error(string) for require/
    revert, and Panic(0xNN) for every panic site now match the EVM
    wire shape, so catch Error(string) / catch Panic(uint) clauses
    match against the canonical data.

By the numbers

Metric v0.15.0 v0.16.0 Delta
Fuzz harnesses passing ~52 409 +357
Tasks resolved this release — ~90 (#94–#183) —
Ignored (known-gap) harnesses 0 1 (#182) +1
Workspace source lines changed — +2,341 / −1,293 56 files
IR variants added — 5 Substr, NewMap, HasKey, StoreParameter, LoadParameter
Fuzz submodules 1 monolith 10 +9 
$ cargo test --test fuzz_tests --release
test result: ok. 409 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out

Highlights

Canonical EVM envelopes everywhere

Every panic site — division by zero, modulus by zero, INT256_MIN / -1,
integer overflow, unary -intN.min, array OOB, pop() on empty, abi.decode
short-buffer — now routes through ir/build/panic.rs::emit_panic, which
emits the 4-byte selector 0x4e487b71 followed by a BE-32 panic code.
Solidity revert("reason") and require(cond, "msg") both emit the
Error(string) envelope. This closes Tasks #103, #107, #108, #131.

Before:

throw "Panic: 0x11"

After:

0x4e487b71 ‖ abi.encode(uint256(0x11))

Narrow Yul + EIP-1153

assembly { ... } blocks now lower mstore/mload/return, let x := ...,
basic arithmetic, and tstore/tload. Transient storage uses a
per-function NEWMAP local with a HasKey guard — unset slots return 0,
matching EIP-1153 semantics. Yul identifiers also resolve to outer
Solidity function parameters via the new StoreParameter / LoadParameter
IR variants (Task #99, #100, #183).

msg.value / msg.data EVM surface

Neo N3 has no intrinsic msg.value. v0.16.0 threads a per-call
pending_value override through NeoRuntime::override_value /
override_sender_and_value, with a dedicated syscall slot returning the
active value. msg.data is synthesised as selector || abi.encode(args)
at the start of each public-method execution (Task #112, #113).

Fuzz suite split

The 24k-line tests/fuzz_tests.rs has been reorganised into 10
submodules under tests/fuzz_tests/:

  • baseline_tests.rs (52 original harnesses)
  • batches_18_30.rs, batches_31_45.rs, batches_46_64.rs, batches_66_80.rs
  • arithmetic_props.rs, compiler_props.rs, optimizer_props.rs, storage_props.rs
  • task107_catch_panic_tests.rs
  • common.rs (shared helpers)

Compatibility notes

The following changes alter observable behaviour for existing contracts.
Review these if you are upgrading a deployed contract:

  1. Integer overflow now reverts. unchecked { ... } blocks remain
    the escape hatch. Contracts that previously relied on silent wrap at
    64-bit on uint256 operands will now observe Panic(0x11).
  2. ~uint256(x) / wide bitwise ops no longer wrap at 64-bit. Results
    match EVM (i.e., ~x == u256::MAX - x). Any contract that relied on
    the broken behaviour will produce different values.
  3. delegatecall is hard-rejected at compile time, not silently
    routed to System.Contract.Call. Migrate to a proxy contract or
    inherit the target. (Task #101.)
  4. Event topic0 is now keccak256(signature) instead of a
    pre-existing Neo-specific placeholder. Off-chain indexers that
    decoded topic0 as a raw opaque value must switch to the EVM
    convention.
  5. catch Panic(uint256) / catch Error(string) now match correctly.
    If your catch blocks depended on the legacy "Panic: 0xNN"
    ByteString shape, they will no longer match — update them to the
    EVM-canonical 4-byte-selector+abi-payload shape.
  6. uint256(bytes32) is a bit-identity reinterpret, not a decode.
    Contracts that implicitly relied on the old behaviour will observe
    different numeric results.
  7. payable(x) is a type-only cast, not a no-op wrap. Manifest
    output is unchanged; source-level analysis may flag different
    warnings.
  8. block.coinbase returns address(0) (already in v0.15.0; stable in
    v0.16.0). It does NOT return getNextBlockValidators().
  9. msg.data outside onNEP17Payment/onNEP11Payment callbacks
    produces selector || abi.encode(args)     (v0.15.0 change, stable in
    v0.16.0).

Known limitations

  • Task #182 — struct { T[] dyn; ... } s; return s.dyn.length; still
    leaks the internal JSON Array shape instead of an EVM-canonical 32-byte BE
    length. Workaround: store the length in a separate uint256 field
    or return it as a top-level expression. The corresponding fuzz
    harness is marked #[ignore].

Oracle integration remains a stub (requires external oracle service) —
unchanged from v0.15.0.

Upgrade guide (v0.15.0 → v0.16.0)

Most contracts need no source changes. The main things to check:

  1. Arithmetic. Anywhere you do a + b, a - b, a * b, ++a,
    a += b on uint256/int256 (or narrow signed), confirm you
    understand the post-op range guard. Wrap explicit overflow paths in
    unchecked { ... }.
  2. Custom errors / try-catch. Confirm your catch clauses match the
    canonical EVM envelope. catch Error(string memory s) { ... } and
    catch Panic(uint256 code) { ... } now work as spec'd.
  3. delegatecall. Any lingering delegatecall needs replacement
    with a proxy pattern or target-contract inheritance. The compile
    error points at the offending call site.
  4. Yul / inline assembly. Narrow yul is now compiled, not warned
    out. If you relied on the v0.15.0 silent-nop for assembly { ... },
    switch to // solhint-disable-next-line no-inline-assembly or strip
    the block — the compiler now emits real code for supported
    primitives.
  5. Devpack users — bump @r3e-network/neo-solidity-devpack to
    ^1.1.0. New Precompiles.sol library available for EVM precompile
    routing (ecrecover, sha256, ripemd160, identity, modexp).

CLI output sanity check

neo-solc --version
# neo-solc 0.16.0

What ships

Core compiler (neo-solidity v0.16.0)

  • src/ir/build/panic.rs — new shared panic envelope emitter.
  • src/ir/ir_types.rs — 5 new IR variants (Substr, NewMap,
    HasKey, StoreParameter, LoadParameter).
  • src/ir/statements/assembly.rs — narrow yul lowering + transient
    storage + yul-to-parameter binding.
  • src/ir/statements/dispatch/return_revert.rs — multi-value return,
    short-decode panic guard, dynamic-array layout, struct custom-error
    envelopes.
  • src/ir/expressions/dispatch/{binary, unary}.rs — checked
    arithmetic for uint256 / int256 / narrow signed.
  • src/runtime/runtime_parts/runtime_impl/runtime/execution.rs —
    msg.data synthesis, per-call msg.value and caller overrides,
    self-method dispatch table.
  • src/runtime/execution/execution_impl_part2_contract_call.rs —
    self-external-call routing through the merged offsets table; virtual
    script hash derivation.
  • src/runtime/execution/helpers/{bitwise, arithmetic, comparison}.rs
    — wide-BigInt path for all wide operands; EIP-145 shift clamping.
  • src/runtime/execution/execution_impl_part2_native/stdlib.rs —
    canonical EVM abi.encode*/abi.decode; itoa / atoi / base64*.

Devpack (@r3e-network/neo-solidity-devpack v1.1.0)

  • devpack/libraries/Precompiles.sol — NEW. EVM precompile routing
    wrappers.
  • devpack/contracts/FrameworkBase.sol — refreshed for the new
    compiler semantics.
  • devpack/standards/NEP17.sol, NEP11.sol — updated to match the
    compiler's Event-canonical wire format.
  • devpack/contracts/NativeCalls.sol, devpack/libraries/{Neo, Runtime, Storage}.sol — aligned with the new runtime bridge.

Acknowledgments

This release was driven by a multi-week fuzz-harness audit. Every task
in this release (#94–#183) resolves a finding raised by an automated
harness, which is documented in the source via // Task #NNN — …
comments for future archaeology.

Thanks to everyone who reviewed diagnostics, staged fixes, and kept the
runtime bridge honest while the compiler caught up with the spec.

Links

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