Building Smart Contracts on Solana: A Beginner's Guide to Rust

Understanding Solana's Execution Environment

1. Solana uses a parallelized runtime called Sealevel, which allows thousands of smart contracts—known as programs—to run simultaneously across different accounts.

2. Unlike Ethereum’s EVM, Solana does not rely on a global state machine; instead, each program operates on isolated account data, enforcing strict ownership and permission models.

3. Programs on Solana are compiled to Berkeley Packet Filter (BPF) bytecode, requiring developers to write in Rust or C and compile down to this target architecture.

4. Account rent exemption is mandatory: every on-chain account must hold enough SOL to cover storage rent, otherwise it risks being purged from the ledger.

5. Transaction fees are deterministic and extremely low, calculated based on compute units consumed rather than gas estimation, making cost prediction more precise.

Setting Up the Rust Development Stack

1. Install rustup via the official Rust installer to manage toolchains, then add the BPF target with rustup target add bpfel-unknown-elf.

2. Use the Solana CLI to configure your local validator, generate keypairs, and deploy programs—commands like solana-test-validator launch a local cluster instantly.

3. Anchor is not required but widely adopted; it abstracts boilerplate such as account serialization, CPI handling, and error definitions into reusable macros and traits.

4. The solana-program crate provides core types like Pubkey, AccountInfo, and ProgramResult, forming the foundation of every Solana program.

5. Debugging relies heavily on logging via msg! macros—these appear in transaction logs and are critical for tracing execution flow during development.

Writing Your First On-Chain Program

1. A minimal program exports an entry_point! macro that accepts instruction data and a slice of account references, serving as the sole interface to the runtime.

2. Instruction deserialization must be explicit—developers parse raw bytes manually or use Anchor’s InstructionData derive macro to auto-generate serializers.

3. Each account passed to the program must be validated for ownership, mutability, signer status, and rent exemption before any state mutation occurs.

4. Programs cannot store arbitrary data structures directly—they persist state by writing serialized bytes into account data buffers, often using Borsh or bincode.

5. Cross-program invocations (CPIs) require constructing instruction structs with properly signed accounts; failing to include a required signer will cause immediate transaction failure.

Testing and Deployment Workflow

1. Unit tests run off-chain using solana-program-test, simulating account creation, instruction submission, and state assertions without network interaction.

2. Integration tests deploy compiled programs to a local test validator and simulate real client interactions using @solana/web3.js in TypeScript.

3. Deploying to devnet requires funding the program address with SOL and executing solana program deploy, which uploads ELF bytecode and assigns a unique Pubkey.

4. Upgradable programs are deployed with buffer accounts and upgrade authorities—this separation enables patching logic without migrating user data.

5. Versioning is manual: there is no built-in contract version registry, so developers embed version identifiers in account data or instruction discriminants.

Frequently Asked Questions

Q: Can I use JavaScript or Python to write Solana smart contracts?A: No. Solana only executes BPF bytecode. Only Rust and C compile reliably to this target. High-level languages may generate client-side logic or IDL definitions but cannot replace on-chain programs.

Q: Why do I get “Account owned by a different program” when trying to modify an account?A: This occurs when the account’s owner field points to another program’s Pubkey. Only the owning program may write to its accounts unless explicitly delegated via CPI or program-derived addresses.

Q: What happens if my program exceeds the compute budget during execution?A: The transaction halts immediately, reverts all state changes, and returns an “ComputationalBudgetExceeded” error. Developers must optimize loops, limit iterations, and avoid unbounded memory allocations.

Q: Is it possible to read another program’s account data without invoking it?A: Yes. Any account marked as non-executable and publicly readable can be fetched via RPC endpoints like getAccountInfo. However, executable programs and private data remain inaccessible without proper permissions.