Effective type
An effective type is the C type through which an object may be accessed under the language’s object-access rules.
Modern C, Third Edition
An effective type is the type that C associates with storage allocated without a declared type through the accesses or stores that establish how the storage may be used.
- How it is used
- Constrains pointer-based access to objects in C's memory model and supports aliasing assumptions.
- How deep it goes
- Defines declared, allocated, character, and union cases, then stops short of detailed alias-analysis mechanics.
- Examples
- Uses malloc-backed double storage, unsigned-char inspection, and an incompatible unsigned-pointer dereference.
- What you can do after
- Apply effective-type rules to allocated storage and diagnose incompatible pointer accesses as undefined behavior.
Modern C
An effective type is the C type through which an object is permitted to be accessed under the language's object-access rules.
- How it is used
- Constrains pointer-based object access and supplies the basis for the aliasing rule.
- How deep it goes
- Defines declared, union, character, and allocated-storage cases, but defers the latter's detailed treatment.
- Examples
- Uses an unsigned-char array cast to unsigned* and allocated storage initialized through assignment.
- What you can do after
- Evaluate pointer-based accesses for effective-type violations and recognize when dereferencing leaves program state undefined.
Related concepts
- alignascontrasts with · alignas, also spelled _Alignas, is an alignment specifier that requests a specified alignment for an object or declaration.
- objectused by · A computational object is a runtime entity or structured value representing data, state, or a resource, with properties or operations defined by its programming model.
- compound literalconfigured by · A compound literal is a C expression consisting of a parenthesized type name followed by an initializer that creates an unnamed object.
- union typecontrasts with · A union type is a type whose values can be any one of several specified alternative types or variants.
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