How do I make use of the extra heap when requesting heap with the compute budget program?

Question

I tried to make a transaction using solana/web3.js ComputeBudgetProgram.requestHeap

I tried a multiple of the default amount, 4 * 32 * 1024 to no avail, program still fails where it did without. I heard I need a custom allocator, is there an example of using one?

https://github.com/solana-labs/solana/blob/ced8f6a512c61e0dd5308095ae8457add4a39e94/sdk/src/compute_budget.rs#L32-L36

Answer 1

To request heap frame, you need to declare custom-heap feature. Without this feature, solana defines global allocator where it assumes 32kb of heap. Once you declare custom-heap feature, you can either define your own allocator using #[allocator] macro or use the default allocator which doesnt assume 32kb of heap and gets the heap amount from the VM configuration shown below.

https://github.com/solana-labs/solana/blob/a2d2eb3ba80824f55c9cbd267ab881a285ca324a/programs/bpf_loader/src/lib.rs#L256 .