Variable-Size Data

Code generation for arrays that change size in the generated code

During code generation, the code generator identifies arrays, including scalars, vectors, and matrices, as either fixed size or variable size.

The code generator designates an array as variable size if it cannot determine the size of the array or if the size of the array changes.
The code generator designates an array as fixed size if it can determine that the size of the array does not change.

Understanding how the code generator handles fixed- and variable-size arrays can help you to diagnose and fix errors during code generation. If your application does not require variable-size arrays, you can also fine-tune variable sizing and dynamic memory allocation to potentially improve the performance of the generated code.

Functions

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

Variable-Sizing Basics

Generate Code for Variable-Size Arrays

Learn how the code generator defines and handles fixed- and variable-size data.

Code Generation for Arrays That Grow Via end+1 Indexing

Code generation considerations when you use (end+1) or {end+1} to grow an array.

Specify Upper Bounds for Variable-Size Arrays in Generated Code

To avoid dynamic memory allocation, specify upper bounds for variable-size arrays.

Incompatibilities with MATLAB in Variable-Size Support for Code Generation

Understand how the behavior of the generated code can differ from MATLAB^® as a result of variable-size data.

Generate Code for a MATLAB Function That Expands a Vector in a Loop

Generate C and C++ code for a function that uses variable-size data with and without dynamically allocated memory.

Dynamic Memory Allocation

Control Dynamic Memory Allocation in Generated Code

Balance memory usage and performance by controlling dynamic memory allocation for fixed- and variable-size arrays.

Generate Code with Implicit Expansion Enabled

The code generator introduces modifications in the generated code to accomplish implicit expansion.

Optimize Implicit Expansion in Generated Code

Implicit expansion in the generated code is enabled by default.

Representation of Arrays in Generated Code

Understand how arrays are represented in the generated code.

Use Dynamically Allocated C Arrays in the Generated Function Interfaces

Understand and use dynamically allocated arrays from the generated C function interfaces.

Use Dynamically Allocated C++ Arrays in Generated Function Interfaces

Understand and use dynamically allocated arrays from the generated C++ function interfaces.

Troubleshooting

Resolve Error: Arrays Have Incompatible Sizes

Troubleshoot size incompatibility errors that occur during code generation.

Resolve Error: Fixed Size on the Left Side but Variable Size on the Right

Troubleshoot errors when assigning variable-size arrays to fixed-size arrays.

Resolve Error: coder.varsize Not Supported for Strings

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

Resolve Error: coder.varsize Not Supported for Class Properties

Troubleshoot code generation error when using coder.varsize with properties of a MATLAB class.

Resolve Error: Unable to Produce Column Vector from Scalar

Troubleshoot error when an input argument that is a variable-length column vector at code generation time is a scalar at run time.

Resolve Error: Incorrect Size for Expression

Troubleshoot MEX function error when the size of an array at run time is incompatible with the size of the array in the generated code.