How to Debug EOSIO based Smart Contract?

To debug a EOS based smart contract, developers are required to firstly setup a local node using nodeos. This local node can take be designated to run as a separate private testnet or as an extension of public testnet. This local node also needs to be run with the contracts-console option on, either --contracts-consolevia the command line or contracts-console = true via the config.ini and/or by setting up logging on your running nodeos node and checking the output logs.

To setup local node as a private testnet, follow the setup guide. By default, your local nodeos will run in a private testnet.

To configure local nodeos as an extension public testnet, you need to modify the config.ini file to connect with public testnet nodes.

Feature Image by MoonX

Caveman Debugging:

This is the main method to debug smart contract that utilizes the printing functionality to inspect the value of a variable and the flow of the contract. Printing in smart contract can be done through the print API.

Print C API supports the following data type that can print:

· Prints — a null terminated char array (string)

· prints_l — any char array (string) with given size

· printi — 64-bit signed integer

· printui — 64-bit unsigned integer

· printi128–128-bit signed integer

· printui128–128-bit unsigned integer

· printsf — single-precision floating point number

· printdf — double encoded as 64-bit unsigned integer

· printqf — quadruple encoded as 64-bit unsigned integer

· printn — 64 bit names as base32 encoded string

· printhex — hex given binary of data and its size

Code examples can be found here: