rethrow — Propagate a caught exception without handling it locally.

rethrow re-raises an exception so that an outer catch block or the embedding runtime can handle it. When you pass an MException, RunMat preserves its identifier and message. Passing a string creates a fresh error with that message. In Ignition-compiled catch blocks, rethrow() with no explicit argument also rethrows the most recently caught exception.

How rethrow works

• rethrow(err) preserves the identifier and message of an MException value.
• rethrow(message) raises a fresh error using the supplied string as the message.
• Other value types produce a generic RunMat:error-style failure describing the value.
• rethrow never returns normally; it immediately transfers control outward to the next enclosing error handler.
• In Ignition catch blocks, rethrow() with no argument uses the most recently caught exception.

How RunMat runs rethrow on the GPU

rethrow performs no provider dispatch; it raises or propagates a host-side runtime error immediately.

GPU memory and residency

rethrow is control flow only and never executes on the GPU.

Examples

Propagate an exception to an outer catch block

try
    try
        error("RunMat:demo:badInput", "Bad input.");
    catch err
        rethrow(err);
    end
catch outer
    disp(outer.identifier)
end

Expected output:

RunMat:demo:badInput

Use the no-argument shorthand inside an Ignition catch block

try
    try
        error("RunMat:oops", "x");
    catch
        rethrow();
    end
catch err
    disp(err.message)
end

Expected output:

x

FAQ

When should I use rethrow instead of error?

Use rethrow when you want to propagate the current exception rather than constructing a new one from scratch.

Does rethrow(err) preserve the original identifier?

Yes. When err is an MException, RunMat preserves both the identifier and the message.

Is rethrow() without an argument supported?

Yes in Ignition catch-block execution, where it reuses the most recently caught exception.

Related Diagnostics functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how rethrow works, line by line, in Rust.

• View rethrow.rs on GitHub
• Learn how the runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code — faster, on any GPU, with no license required.

• Simulations that took hours now take minutes. RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed.
• Start running code in seconds. Open the browser sandbox or download a single binary. No license server, no IT ticket, no setup.
• A full development environment. GPU-accelerated 2D and 3D plotting, automatic versioning on every save, and a browser IDE you can share with a link.

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