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Solidity / Security & Advanced

reentrancy guard

Learn reentrancy guard in Solidity through a focused explanation, a dedicated construct-specific example, an engineering boundary, and a mastery check.

10 min read • Advanced

reentrancy guard is an atomic Solidity topic inside Security & Advanced. This lesson focuses on how the reentrancy guard construct is written, what it changes, and when it is the right tool.

Trace the example line by line. Identify the exact syntax for reentrancy guard, the input state before it runs, and the resulting value, control flow, database state, hardware behavior, or runtime effect afterward. Neighboring lessons use different constructs rather than renamed copies of this one.

Topic-specific example

solidity-08-02-reentrancy-guard.sol
solidity Try It Live 
contract C { bool locked; modifier nonReentrant(){require(!locked);locked=true;_;locked=false;} function act() external nonReentrant{} }
Edge case / engineering note

For reentrancy guard, test the boundary that belongs to this exact feature rather than a generic failure case. Check invalid or empty input, NULL/unknown state, numeric limits, transaction or exception behavior, synthesis/runtime constraints, ownership/permission rules, or backtracking/control-flow effects where they apply.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

reentrancy guard Mastery Check →
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