Generate MISRA Compliant Code and Verify with Polyspace

R2026b

When generating C code for your MATLAB® code base, you can configure the code generator to produce code that is compliant with a large subset of the MISRA C™:2023 guidelines. See MISRA C:2023 Coding Directives and Rules Supported for Code Generation (Embedded Coder).

This example consists of the following steps:

• Create and run a MATLAB entry-point function that uses the fft and islocalmax functions to perform basic spectral analysis on an input time-domain signal.

• Generate and run a MEX function for this MATLAB function to check for potential run-time issues in the generated code.

• Generate standalone C source code that is compliant with a large subset of the MISRA C:2023 guidelines by using the coder.setupMISRAConfig (Embedded Coder) and codegen (MATLAB Coder) functions.

• Perform static analysis by using Polyspace® Bug Finder™ to check the compliance of the generated code with the MISRA C:2023 guidelines.

Define MATLAB Entry-Point Function

Define an entry-point function powerSpectrumPeaks that calculates the Fourier transform of a time-domain signal sampled at frequency fs. The function then squares the absolute value of the Fourier transform to obtain the power spectrum of the signal in the frequency domain. Finally, it returns the frequencies at which the peaks of the power spectrum, which have a pre-specified minimum prominence, are located.

type powerSpectrumPeaks.m

function peaks = powerSpectrumPeaks(signal,fs,prominence)
n = length(signal);
signalIndices = 1:n;

y = fft(signal);
power = abs(y).^2/n;

peakIndices = signalIndices(islocalmax(power,MinProminence=prominence));
peaks = (peakIndices - 1)*fs/n;
end

Define a complex time-domain signal that has two frequency components at 50 Hz and 300 Hz.

fs = 1000;            % Sampling frequency                    
T = 1/fs;             % Sampling period       
L = 1500;             % Length of signal
t = (0:L-1)*T;        % Time vector
x = 0.7*exp(2*1i*pi*50*t) + 1.3*exp(2*1i*pi*300*t);  % Input signal

To filter out the noise from the power spectrum, define a minimum peak prominence that the islocalmax function uses.

prominence = 0.001;

Call the entry-point function powerSpectrumPeaks with these inputs. The function returns a 2-by-1 array that contains the two component frequencies of the input signal.

powerSpectrumPeaks(x,fs,prominence)

ans = 1×2

    50    300

Check for Run-Time Issues by Generating and Running MEX

Use the codegen command to generate a MEX function for the powerSpectrumPeaks function. Provide the example input values defined in the previous section to the -args argument.

codegen powerSpectrumPeaks -args {x,fs,prominence} -d mexcode

Code generation successful.

Run the generated MEX function with the same inputs. The output of the MEX function matches that of MATLAB execution.

powerSpectrumPeaks_mex(x,fs,prominence)

ans = 1×2

    50    300

Generate MISRA Compliant Standalone C Source Code

Create a coder.EmbeddedCodeConfig (MATLAB Coder) object for generating standalone C source code. For improved compliance of the generated code with the MISRA C:2023 guidelines, use the coder.setupMISRAConfig function to configure this object.

cfg = coder.config('lib','ecoder',true);
cfg.GenCodeOnly = true;
coder.setupMISRAConfig(cfg);

Generate standalone C source code for the powerSpectrumPeaks function. Specify the code generation folder as misracompliantcode.

codegen -config cfg powerSpectrumPeaks -args {x,0,0} -d misracompliantcode -report

Code generation successful: View report

Run Static Analysis on Generated Code at Command Line

Use Polyspace Bug Finder to statically check for compliance of the generated code with the subset of MISRA C:2023 rules and directives that are categorized as either mandatory or required. The MISRA C:2023 standard performs this categorization slightly differently for user-written code and automatically generated code. In this example, you use the categorization for automatically generated code.

Create a polyspace.ModelLinkOptions object psprjCfg for static analysis with Polyspace Bug Finder. Specify misracompliantcode as the code generation folder.

codegenfolder = fullfile(pwd,'misracompliantcode');
psprjCfg = polyspace.ModelLinkOptions('-codegenfolder', codegenfolder);

To configure the static analysis, run this system command:

polyspace-checkers-selection

This command opens the Checkers selection window. In this window:

• Select Defects. Clear the check boxes to deselect the Bug Finder defects activated by default.

• Select MISRA C:2023. Activate the mandatory and required rules by checking the Mandatory and Required check boxes.

• To use the categorization for automatically generated code, select Use generated code requirements.

• Save the activation file as misrachecker.xml

After creating the checker activation file, specify the file in the property CheckersSelectionFile. Additionally, to suppress the printing of the log when you run the analysis, specify the option -quiet as an additional option.

psprjCfg.CodingRulesCodeMetrics.CheckersSelectionFile = fullfile(pwd,"misrachecker.xml");
psprjCfg.Advanced.Additional = '-quiet';

Create a polyspace.Project object and specify psprjCfg as the configuration:

proj = polyspace.Project;
proj.Configuration = psprjCfg;

Use the proj object to run the analysis.

proj.run('bugFinder');

Import the analysis results into a table by using the polyspace.BugFinderResults object and the getResults object function. Use the function groupsummary to display the number of violations for each rule or directive.

resObj = proj.Results;
resTable = getResults(resObj, 'readable');
groupsummary(resTable,'Check')

ans = 7×2 table
                                         Check                                         GroupCount
    _______________________________________________________________________________    __________

    10.1 Operands shall not be of an inappropriate essential type.                          4    
    11.3 A conversion shall not be performed between a pointer to object type and …        10    
    14.3 Controlling expressions shall not be invariant.                                    3    
    18.1 A pointer resulting from arithmetic on a pointer operand shall address an…         1    
    9.1 The value of an object with automatic storage duration shall not be read b…         5    
    Dir 1.1 Any implementation-defined behaviour on which the output of the progra…        16    
    Dir 4.15 Evaluation of floating-point expressions shall not lead to the undete…        25    

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The generated code is compliant with a large subset of the mandatory and required categories of the MISRA C:2023 standard.