Read access violation _Mem was nullptr

#1

Hi, I’m a complete beginner to JUCE. I’ve been following along to this video right here: Learn Modern C++ by Building an Audio Plugin (w/ JUCE Framework) - Full Course - YouTube

Recently I’ve ran into an error that has me completely stumped. Whenever I try to debug I’m met with the error "Exception thrown: read access violation. _Mem was nullptr.

I went to the place where the call stack showed the exception happening which is right here. I’ve checked but no matter what I seem to do, nothing will fix it.

issue Photo 2
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Does anyone know what might be causing this? Thanks

#2

Here’s the image of the main error

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issue Photo 11920×917 154 KB

#3

this is nullptr

You’re using an invalid object

Rail

#4

Hey, I am having the exact same issue, did you ever figure it out?

#5

Same here, everything been going fine then this suddenly pops up for as far as I can tell, no apparent reason?

I’m using an ‘Invalid Object’, which one?

Why does Visual Studio show No Issues but then it throws this up when you try and debug?

#6

Because this is a runtime issue, not a compile time issue.

And it’s not for “No apparent reason”, you have a bug. You need to learn how to debug, so you can find and fix your bug.

#7

OK yes that makes sense, because even the Plugin Window pops up for a second then disappears, that’s a clue!

I need to learn to debug, yep I do :frowning:

2 Likes
#8

let me know if you figure it out, ill do the same :grin:

#9

NoahW29, I did figure it out, it was a Copy & Paste error, Doh!

Inside the PluginProcessor.cpp and the getChainSettings function I had:

settings.peakBypassed = apvts.getRawParameterValue(“Peak Bypassed”)->load() > 0.5f;

But inside the createParameterLayout function I had:

layout.add(std::make_uniquejuce::AudioParameterBool(“PeakCut Bypassed”, “PeakCut Bypassed”, false));

Not sure why the Compiler didn’t pick that up, and the Error made no sense to me, I found it by just back tracking and commenting out line by line till it didn’t crash anymore!

1 Like
#10

Two words of advice here:

Don’t copy&paste strings (actually don’t copy&paste at all, but that is a different story).
Instead define the paramIDs as constexpr or static strings:

class MyAudioProcessor // ...
{
    static constexpr auto cutoffID = "PeakCut Bypassed";
}
// ...
{
    settings.peakBypassed = apvts.getRawParameterValue (MyAudioProcessor::cutoffID)->load() > 0.5f;
}

The compiler doesn’t read string literals at all. Those will only be found at runtime.

Second advice:
Don’t use the getRawParameterValue() in the processing, as it is a slow method.
Instead keep a pointer to the properly casted version. Of course you need to change the ChainSettings a bit, because at the moment that is copied and destroyed a lot.
If the getChainSettings() method was a method of the processor, you could store the pointers in the processor.