hevm symbolic

Usage: hevm symbolic [--code TEXT] [--calldata TEXT] [--address ADDR]
                     [--caller ADDR] [--origin ADDR] [--coinbase ADDR]
                     [--value W256] [--nonce WORD64] [--gas WORD64]
                     [--number W256] [--timestamp W256] [--basefee W256]
                     [--priority-fee W256] [--gaslimit WORD64] [--gasprice W256]
                     [--create] [--maxcodesize W256] [--prev-randao W256]
                     [--chainid W256] [--rpc TEXT] [--block W256]
                     [--root STRING] [--project-type PROJECTTYPE]
                     [--initial-storage INITIALSTORAGE] [--sig TEXT]
                     [--arg STRING]... [--get-models] [--show-tree]
                     [--show-reachable-tree] [--smttimeout NATURAL]
                     [--max-iterations INTEGER] [--solver TEXT] [--smtdebug]
                     [--assertions [WORD256]] [--ask-smt-iterations INTEGER]
                     [--num-solvers NATURAL]
                     [--loop-detection-heuristic LOOPHEURISTIC]

Available options:
  -h,--help                Show this help text
  --code TEXT              Program bytecode
  --calldata TEXT          Tx: calldata
  --address ADDR           Tx: address
  --caller ADDR            Tx: caller
  --origin ADDR            Tx: origin
  --coinbase ADDR          Block: coinbase
  --value W256             Tx: Eth amount
  --nonce WORD64           Nonce of origin
  --gas WORD64             Tx: gas amount
  --number W256            Block: number
  --timestamp W256         Block: timestamp
  --basefee W256           Block: base fee
  --priority-fee W256      Tx: priority fee
  --gaslimit WORD64        Tx: gas limit
  --gasprice W256          Tx: gas price
  --create                 Tx: creation
  --maxcodesize W256       Block: max code size
  --prev-randao W256       Block: prevRandao
  --chainid W256           Env: chainId
  --rpc TEXT               Fetch state from a remote node
  --block W256             Block state is be fetched from
  --root STRING            Path to project root directory (default: . )
  --project-type PROJECTTYPE
                           Is this a Foundry or DappTools project (default:
  --initial-storage INITIALSTORAGE
                           Starting state for storage: Empty, Abstract (default
  --sig TEXT               Signature of types to decode / encode
  --arg STRING             Values to encode
  --get-models             Print example testcase for each execution path
  --show-tree              Print branches explored in tree view
  --show-reachable-tree    Print only reachable branches explored in tree view
  --smttimeout NATURAL     Timeout given to SMT solver in seconds (default: 300)
  --max-iterations INTEGER Number of times we may revisit a particular branching
  --solver TEXT            Used SMT solver: z3 (default), cvc5, or bitwuzla
  --smtdebug               Print smt queries sent to the solver
  --assertions [WORD256]   Comma separated list of solc panic codes to check for
                           (default: user defined assertion violations only)
  --ask-smt-iterations INTEGER
                           Number of times we may revisit a particular branching
                           point before we consult the smt solver to check
                           reachability (default: 1) (default: 1)
  --num-solvers NATURAL    Number of solver instances to use (default: number of
                           cpu cores)
  --loop-detection-heuristic LOOPHEURISTIC
                           Which heuristic should be used to determine if we are
                           in a loop: StackBased (default) or Naive
                           (default: StackBased)

Run a symbolic execution against the given parameters, searching for assertion violations.

Counterexamples will be returned for any reachable assertion violations. Where an assertion violation is defined as either an execution of the invalid opcode (0xfe), or a revert with a message of the form abi.encodeWithSelector('Panic(uint256)', errCode) with errCode being one of the predefined solc assertion codes defined here.

By default hevm ignores assertion violations that result from arithmetic overflow (Panic(0x11)), although this behaviour can be customised via the --assertions flag. For example, the following will return counterexamples for arithmetic overflow (0x11) and user defined assertions (0x01):

hevm symbolic --code $CODE --assertions '[0x01, 0x11]'

The default value for calldata and caller are symbolic values, but can be specialized to concrete functions with their corresponding flags.

One can also specialize specific arguments to a function signature, while leaving others abstract. If --sig is given, calldata is assumed to be of the form suggested by the function signature. With this flag, specific arguments can be instantiated to concrete values via the --arg flag.

This is best illustrated through a few examples:

Calldata specialized to the bytestring 0xa9059cbb followed by 64 symbolic bytes:

hevm symbolic --sig "transfer(address,uint256)" --code $(<dstoken.bin-runtime)

Calldata specialized to the bytestring 0xa9059cbb0000000000000000000000007cfa93148b0b13d88c1dce8880bd4e175fb0dedf followed by 32 symbolic bytes.

hevm symbolic --sig "transfer(address,uint256)" --arg 0x7cFA93148B0B13d88c1DcE8880bd4e175fb0DeDF --code $(<dstoken.bin-runtime)

Calldata specialized to the bytestring 0xa9059cbb followed by 32 symbolic bytes, followed by the bytestring 0000000000000000000000000000000000000000000000000000000000000000:

hevm symbolic --sig "transfer(address,uint256)" --arg "<symbolic>" --arg 0 --code $(<dstoken.bin-runtime)

If the --get-models flag is given, example input values will be returned for each possible execution path. This can be useful for automatic test case generation.

The default timeout for SMT queries is no timeout. If your program is taking longer than a couple of minutes to run, you can experiment with configuring the timeout to somewhere around 10s by doing --smttimeout 10000

Storage can be initialized in two ways:

  • Empty: all storage slots for all contracts are initialized to zero
  • Abstract: all storage slots are initialized as unconstrained abstract values

hevm uses an eager approach for symbolic execution, meaning that it will first attempt to explore all branches in the program (without querying the smt solver to check if they are reachable or not). Once the full execution tree has been explored, the postcondition is checked against all leaves, and the solver is invoked to check reachability for branches where a postcondition violation could occur. While our tests have shown this approach to be significantly faster, when applied without limits it would always result in infinite exploration of code involving loops, so after some predefined number of iterations (controlled by the --ask-smt-iterations flag), the solver will be invoked to check whether a given loop branch is reachable. In cases where the number of loop iterations is known in advance, you may be able to speed up execution by setting this flag to an appropriate value.