Known Issues

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Dictionaries with extra builtins or untaken dict paths

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What fails

1. Use a dictionary (Felt252Dict / SegmentArena) together with other builtins such as Poseidon or Bitwise (for example hades_permutation or bitwise ops), or
2. Contain dict code on a branch that is not taken for the given inputs (SegmentArena is still an implicit of main, but no dict is allocated at runtime).

VirtualMachine(Math(RelocatableSubUsizeNegOffset((Relocatable { segment_index: N, offset: 0 }, 2))))
VirtualMachine(Memory(AddressNotRelocatable))
VirtualMachine(Hint((0, VariableNotInScopeError("dict_manager_exec_scope"))))

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Why it happens

1. Serializes outputs with CASM rescope blocks, which drop AP-relative variables, including the live SegmentArena pointer.
2. Tries to recover SegmentArena from a hard-coded FP offset (fp + 2 * builtins.len() + 2). That cell holds the initial arena pointer (base+3), not the pointer main returned. Dict alloc/destruct copies the 3-cell header forward, so validation against the initial pointer is wrong (often a silent no-op). Extra builtins (Poseidon, Bitwise) or gas can shift that FP cell onto a felt or a segment base, which leads to RelocatableSubUsizeNegOffset / AddressNotRelocatable.
3. Always emits the RelocateAllDictionaries cheatcode when SegmentArena is present. The dict manager exec scope is only created when a dict is actually allocated. If dict types appear in Sierra but the taken path never allocates one, the hint crashes with VariableNotInScopeError("dict_manager_exec_scope").

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Workaround until PR is merged

1. Use the Herodotus fork (includes the fix): https://github.com/HerodotusDev/starkware-cairo-vm/tree/main
2. Build and run cairo1-run against your Sierra (gas disabled is recommended for this runner):
   git clone https://github.com/HerodotusDev/starkware-cairo-vm.git
   cd starkware-cairo-vm
   cargo build -p cairo1-run --release
   
   ./target/release/cairo1-run path/to/program.sierra.json \
     --layout all_cairo \
     --append_return_values \
     --cairo_pie_output ./pie.zip \
     --args_file path/to/input.txt
   
3. Submit pie.zip to Atlantic with pieFile and the desired result (PROOF_GENERATION, PROOF_VERIFICATION_ON_L1, or PROOF_VERIFICATION_ON_L2). See Sending Query — Input: Trace File.

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poseidon_hash_span / corelib gas helpers (get_builtin_costs)

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Official documentation

• Libfunc get_builtin_costs & function poseidon_hash_many

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Important: not only Poseidon hash-span

VirtualMachine(FailedToComputeOperands(...))

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What to use instead

use core::array::{ArrayTrait, SpanTrait};
use core::hash::HashStateTrait;
use core::poseidon::{hades_permutation, HashState};

// Modified version of poseidon_hash_span that doesn't require builtin gas costs
pub fn poseidon_hash_span(mut span: Span<felt252>) -> felt252 {
    _poseidon_hash_span_inner((0, 0, 0), ref span)
}

fn _poseidon_hash_span_inner(
    state: (felt252, felt252, felt252),
    ref span: Span<felt252>,
) -> felt252 {
    let (s0, s1, s2) = state;
    let x = *match span.pop_front() {
        Option::Some(x) => x,
        Option::None => { return HashState { s0, s1, s2, odd: false }.finalize(); },
    };
    let y = *match span.pop_front() {
        Option::Some(y) => y,
        Option::None => { return HashState { s0: s0 + x, s1, s2, odd: true }.finalize(); },
    };
    let next_state = hades_permutation(s0 + x, s1 + y, s2);
    _poseidon_hash_span_inner(next_state, ref span)
}

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Large program outputs (~3700+ felts)

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What fails

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Recommended approach

pub fn main(mut input: Array<felt252>) -> Array<felt252> {
    let mut output: Array<felt252> = array![];
    // Some operation on that array
    // ...

    output
}

pub fn main(mut input: Array<felt252>) -> Array<felt252> {
    let mut output: Array<felt252> = array![];
    // Some operation on that array
    // ...

    // Use the gas-free poseidon_hash_span from the section above —
    // not core::poseidon::poseidon_hash_span
    array![poseidon_hash_span(output.span())]
}