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_Follow along with this video:_ --- ### Runtime Code With `contract creation` understood, we move onto the runtime section of our op codes. Remember, Solidity conveniently will break each of theses sections up by adding an `INVALID` op code between them. <details> <Summary> Op Codes </summary> bytecode - 0x6080604052348015600e575f80fd5b5060a58061001b5f395ff3fe6080604052348015600e575f80fd5b50600436106030575f3560e01c8063cdfead2e146034578063e026c017146045575b5f80fd5b6043603f3660046059565b5f55565b005b5f5460405190815260200160405180910390f35b5f602082840312156068575f80fd5b503591905056fea2646970667358fe1220fe01fe6c40d0ed98f16c7769ffde7109d5fe9f9dfefe31769a77032ceb92497a64736f6c63430008140033 ```js PUSH1 0x80 ✅ PUSH1 0x40 ✅ MSTORE ✅ CALLVALUE ✅ DUP1 ✅ ISZERO ✅ PUSH1 0x0e ✅ JUMPI ✅ PUSH0 ✅ DUP1 ✅ REVERT ✅ JUMPDEST ✅ POP ✅ PUSH1 0xa5 ✅ DUP1 ✅ PUSH2 0x001b ✅ PUSH0 ✅ CODECOPY ✅ PUSH0 ✅ RETURN ✅ INVALID ✅ PUSH1 0x80 //<---- We are here! PUSH1 0x40 MSTORE CALLVALUE DUP1 ISZERO PUSH1 0x0e JUMPI PUSH0 DUP1 REVERT JUMPDEST POP PUSH1 0x04 CALLDATASIZE LT PUSH1 0x30 JUMPI PUSH0 CALLDATALOAD PUSH1 0xe0 SHR DUP1 PUSH4 0xcdfead2e EQ PUSH1 0x34 JUMPI DUP1 PUSH4 0xe026c017 EQ PUSH1 0x45 JUMPI JUMPDEST PUSH0 DUP1 REVERT JUMPDEST PUSH1 0x43 PUSH1 0x3f CALLDATASIZE PUSH1 0x04 PUSH1 0x59 JUMP JUMPDEST PUSH0 SSTORE JUMP JUMPDEST STOP JUMPDEST PUSH0 SLOAD PUSH1 0x40 MLOAD SWAP1 DUP2 MSTORE PUSH1 0x20 ADD PUSH1 0x40 MLOAD DUP1 SWAP2 SUB SWAP1 RETURN JUMPDEST PUSH0 PUSH1 0x20 DUP3 DUP5 SUB SLT ISZERO PUSH1 0x68 JUMPI PUSH0 DUP1 REVERT JUMPDEST POP CALLDATALOAD SWAP2 SWAP1 POP JUMP INVALID LOG2 PUSH5 0x6970667358 INVALID SLT KECCAK256 INVALID ADD INVALID PUSH13 0x40d0ed98f16c7769ffde7109d5 INVALID SWAP16 SWAP14 INVALID INVALID BALANCE PUSH23 0x9a77032ceb92497a64736f6c63430008140033 ``` </details> This section of code is the `runtime code` this is what is copied to the blockchain and represents the entry point of all calls sent to its address. The next chunk we'll assess should look familiar to us! Let's break it down. ```js // Free Memory Pointer PUSH1 0x80 PUSH1 0x40 MSTORE //msg.value check CALLVALUE // [msg.value] DUP1 // [msg.value, msg.value] ISZERO // [msg.value == 0, msg.value] PUSH1 0x0e // [0x0e, msg.value == 0, msg.value] JUMPI // [msg.value] // Jump to "continue!" if msg.value == 0 PUSH0 // [0x00, msg.value] DUP1 // [0x00, 0x00, msg.value] REVERT // [] // If msg.value == 0, start here! // continue! JUMPDEST POP ``` What's happening above? The first three codes are Solidity's `free memory pointer` again! We'll get used to seeing this. From there we see another chunk we've seen before - the msg.value check. The Solidity compiler is smart enough to check all the functions within a contract and determine if any of them are payable. If none of a contract's functions are payable, any call data sent to the contract's runtime code will be checked for value and the transaction will revert if any is found! We'll continue from the `JUMPDEST` in the next lesson to see how a call is handled when `msg.value == 0`.
A comprehensive breakdown of a Solidity Smart Contract's Runtime Code. The lesson covers the runtime code, which is the first part of the code executed on the blockchain, as well as the entry point to all calls made to the smart contract.
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Course Overview
About the course
Assembly
Writing smart contracts using Huff and Yul
Ethereum Virtual Machine OPCodes
Formal verification testing
Smart contract invariant testing
Halmos, Certora, Kontrol
Security researcher
$49,999 - $120,000 (avg. salary)
Smart Contract Auditor
$100,000 - $200,000 (avg. salary)
Guest lecturers:
Josselin Feist
Head of Blockchain at Trail of Bits
Last updated on January 17, 2025
Solidity Developer
Assembly and Formal VerificationDuration: 30min
Duration: 4h 38min
Duration: 3h 57min
Duration: 1h 56min
Course Overview
About the course
Assembly
Writing smart contracts using Huff and Yul
Ethereum Virtual Machine OPCodes
Formal verification testing
Smart contract invariant testing
Halmos, Certora, Kontrol
Security researcher
$49,999 - $120,000 (avg. salary)
Smart Contract Auditor
$100,000 - $200,000 (avg. salary)
Guest lecturers:
Josselin Feist
Head of Blockchain at Trail of Bits
Last updated on January 17, 2025
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