Variable-Size Data

Definition and differences for code generation

You can specify variables in MATLAB Function and MATLAB System blocks as variable-size, which is data whose size is not known at compile time or changes at run time.

Blocks

MATLAB Function	Include MATLAB code in Simulink models
MATLAB System	Include System object in model

Functions

`coder.areUnboundedVariableSizedArraysSupported`	Check if current configuration settings allow unbounded variable-size arrays (Since R2024a)
`coder.varsize`	Resolve size mismatch errors and declare upper bounds

Topics

Code Generation for Variable-Size Arrays
Variable-size data is data whose size is not known at compile time or whose size can change at run time.
Declare Variable-Size MATLAB Function Block Variables
Allow variables defined in MATLAB Function blocks to change size during simulation.
Unbounded Variable-Size Signals
Model unknown size data using dynamic arrays.
Define Variable-Size Data for Code Generation
Choose a method for defining variable-size data.
Use Dynamic Memory Allocation for Variable-Size Arrays in a MATLAB Function Block
Generate C/C++ code that uses dynamic memory allocation.
Control Memory Allocation for Variable-Size Arrays in a MATLAB Function Block
Disable dynamic memory allocation or specify a dynamic memory allocation threshold for MATLAB Function blocks.
Specify Upper Bounds for Variable-Size Arrays
To avoid dynamic memory allocation, specify upper bounds for a variable-size array.
Incompatibilities with MATLAB in Variable-Size Support for Code Generation
Sometimes, the results for variable-size data in generated code are different than the results in MATLAB^®.
Variable-Sizing Restrictions for Code Generation of Toolbox Functions
Some restrictions for variable-size data apply to multiple toolbox functions.

Troubleshooting

Diagnose and Fix Variable-Size Data Errors

Troubleshoot size mismatch and upper bounds detection errors.

Resolve Issue: coder.varsize Not Supported for Strings

Troubleshoot code generation error when using coder.varisze with string variables.

Featured Examples

Unbounded Variable-Size Signal Basic Operations

Use unbounded variable-size signals in Simulink® modeling. For more information about the general concept of unbounded variable-size signals, see Unbounded Variable-Size Signal.

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