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Debug Generated Code During SIL Simulation

If a software-in-the-loop (SIL) simulation fails or you notice differences between the outputs of your original functions and the generated code, you can rerun the SIL simulation with a debugger enabled. By inserting breakpoints, you can observe the behavior of code sections, which can help you to understand the cause of the issue.

For a SIL simulation failure, you can also view information from the standard output and standard error streams in the Diagnostic Viewer. For example:

  • Output from printf statements in your code.

  • Error messages sent to stderr.

  • Some low-level system messages.

During a SIL simulation, the SIL application redirects the stdout and stderr streams. When the application terminates, the Diagnostic Viewer displays the information from the redirected streams. The SIL application also provides a basic signal handler, which captures the POSIX® signals SIGFPE, SIGILL, SIGABRT, and SIGSEV. For this signal handler, the SIL application includes the file signal.h.

A SIL simulation supports these debuggers;

  • On Windows®, Microsoft® Visual Studio® debugger.

  • On macOS, LLDB Debugger (LLDB).

  • On Linux®, GNU® Data Display Debugger (DDD).


You can perform SIL debugging only if the Simulink® product family supports your Microsoft Visual C++®, Xcode, or GNU GCC compiler. For more information, see supported compilers.

To enable your debugger for a SIL simulation, perform one of these actions:

  • On the SIL/PIL tab, click Settings > SIL Debugging.

  • In the Configuration Parameters dialog box, select the Enable source-level debugging for SIL check box.

If your top model has Model blocks, the Enable source-level debugging for SIL parameter for the top model overrides the corresponding parameter for referenced models.

When you run the SIL simulation, for example on a Windows computer, your model.c or model.cpp file opens in the Microsoft Visual Studio IDE with debugger breakpoints at the start of the model_initialize and model_step functions.

You can now use the debugger features to observe code behavior. For example, you can step through code and examine variables.

To end the debugging session:

  1. Remove all breakpoints.

  2. Click the Continue button (F5).

    The SIL simulation runs to completion and the Microsoft Visual Studio IDE closes.


In the Microsoft Visual Studio IDE, if you select Debug > Stop Debugging, the SIL simulation times out with the following error message:

The timeout of 1 seconds for receiving data from the rtiostream 
interface has been exceeded. There are multiple possible causes 
for this failure.

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