Lifetime
A lifetime is the interval during which a program entity exists and remains valid or accessible under the applicable language rules.
Modern C, Third Edition
An object's lifetime is the interval of program execution during which the object exists and can be accessed according to the language rules.
- How it is used
- Checks whether pointers and expressions still access existing C objects as execution crosses blocks, calls, loops, and jumps.
- How deep it goes
- Defines the access rule, distinguishes four storage durations, and works through automatic objects and compound literals; VLA and temporary rules remain separate.
- Examples
- Contrasts shadowed locals, repeated visits to a compound literal via goto, and a pointer retained after a while loop.
- What you can do after
- Diagnose/debug with it whether an object remains accessible after a block, loop iteration, or jump.
Learn Rust in a Month of Lunches
A variable lifetime is the interval during which a variable binding is valid and accessible.
- How it is used
- Uses lifetimes to determine when block-local variables end and whether references remain valid.
- How deep it goes
- Develops block scope, function returns, and named and anonymous annotations through examples and compiler errors, without explaining compiler internals.
- Examples
- Uses an out-of-scope number, a returned string literal, and a struct borrowing a city name.
- What you can do after
- Diagnose/debug with it by reading lifetime errors and choosing owned returns, `'static` literals, or named lifetimes as appropriate.
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Refactoring to Rust
A lifetime is the period during which a value remains valid between allocation and being dropped.
- How it is used
- Uses lifetimes to reason about when owned values and borrowed references remain valid, including when sharing memory across FFI boundaries.
- How deep it goes
- Works from scope and move diagrams through compiler errors to named annotations relating input and output references.
- Examples
- Contrasts a borrowed vector element with a reference to a local variable, then adds an argument that requires a named lifetime.
- What you can do after
- Diagnose/debug with lifetime graphs and compiler errors, then annotate a function when its returned reference must be tied to an input.
Modern C
Object lifetime is the interval during program execution in which a C object exists and may be accessed according to the language rules.
- How it is used
- Determines whether an object remains accessible as pointers, scopes, and control flow change.
- How deep it goes
- Defines the access rule and distinguishes storage durations, then works through shadowing, loop, and goto cases; defers concrete machine models.
- Examples
- Uses a shadowed local variable, a revisited compound literal, and contrasting while and goto snippets.
- What you can do after
- Diagnose/debug with it whether a saved pointer still refers to a live object after a loop or jump.
Idiomatic Rust
A Rust lifetime is a compile-time property describing how long a reference or borrow remains valid.
- How it is used
- Tracks the validity of borrowed references in struct fields, method returns, and iterator item types.
- How deep it goes
- Defines named lifetimes and `'static`, then applies annotations to borrowed iterator signatures without establishing the safety of their unsafe implementation.
- Examples
- Uses a borrowed string field, explicit and implicit function annotations, and linked-list iterators yielding references or owned values.
- What you can do after
- Apply it via Rust lifetime annotations to express borrowed fields and iterator items, while recognizing where inference suffices.
Functional Design and Architecture: Examples in Haskell
The lifetime of an abstraction is the span of program development or execution stages during which that abstraction remains present and meaningful.
- How it is used
- Frames state, runtime objects, interfaces, and resources by the stages or scopes in which they remain meaningful.
- How deep it goes
- Defines lifetime, classifies state durations, traces runtime scopes, and gives a resource-management pattern with nested cleanup.
- Examples
- Uses controller instances, devices, local and external state, Sentry services, and nested resource brackets.
- What you can do after
- Designs state and runtime resources around explicit scopes, and diagnoses retention or cleanup risks.
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Rust in Action: Systems programming concepts and techniques
A lifetime is the statically determined span during which a Rust value or reference remains valid.
- How it is used
- Defines when values and references can be accessed, helping explain Rust borrow-checker errors.
- How deep it goes
- Explains lifetime annotations and a worked move error, without detailing the compiler’s lifetime-inference rules.
- Examples
- Uses an annotated two-reference addition function and a satellite-status program that fails on reuse of a moved value.
- What you can do after
- Diagnose/debug with it by distinguishing a variable’s scope from the valid lifetime of its moved value.
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Rust Servers, Services, and Apps
A Rust annotation and analysis concept describing how long references are valid.
- How it is used
- Models borrowed fields inside HTTP response structs while Rust checks that referenced data remains valid.
- How deep it goes
- Defines reference validity and applies one annotation across a response struct, but does not develop advanced lifetime relationships.
- Examples
- Uses `HttpResponse<'a>`, borrowed headers and strings, response constructors, getters, serialization, and HTTP response tests.
- What you can do after
- Build it from scratch by annotating borrowed response fields and implementing tested constructors, accessors, and serialization.
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Related concepts
- static lifetimeincludes · In Rust, the static lifetime is a lifetime that extends for the entire duration of the program.
- referenceconfigures · A reference is an indirect value or relationship that identifies or provides access to another value, object, resource, or source.
- variable-length arraycontrasts with · A variable-length array is an array whose bound is determined at run time rather than fixed as a compile-time constant.
- compileruses · A compiler is software that translates source code into executable code or another representation, while analyzing it according to the source language’s rules.
- scopecontrasts with · Scope is the region of a program in which names are visible and can be resolved according to the language’s lookup rules.
- borrow checkerused by · A borrow checker is a compile-time mechanism that verifies ownership, borrowing, and reference rules to prevent invalid memory access.
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