SOLVED: Plug'nScript Native Code Issue

[Minisonic]

Can anyone enlighten me as to why this simple C++ code (when compiled into a bin file with Xcode on a Mac) crashes PnS upon loading it. If it doesn't crash on the first load it will crash after hitting the reload button once or twice.

I have built a debug version and attached a debugger to PnS and the initialize function completes successfully. Since I don't have a debug build of PnS I can't really tell what's happening after that as Xcode can only display the assembly language.

A couple of clues, perhaps:
- The problem goes away if the line calling to the .resize method is removed, although that method does execute successfully in the debugger.
- The crash always happens in a routine called libsystem_platform.dylib`_platform_strlen

Any ideas anyone?

The Code

Code: Select all

/*
 *   RMS Level Integrator
 */
#include "./dspapi.h"
#include "./cpphelpers.h"
#include <math.h>


DSP_EXPORT uint audioInputsCount=0;

// metadata
DSP_EXPORT string name="RMS Integrator";
DSP_EXPORT string author="Centripidity";
DSP_EXPORT string description="Averages RMS level of each channel.";


// output parameters definition
DSP_EXPORT array<string> outputParametersNames={};

bool initialised = false;

DSP_EXPORT bool initialize() {
  if(!initialised) {
    outputParametersNames.resize(audioInputsCount);
    initialised = true;
  }
  return true;
}

Peter

[Blue Cat Audio]

When you resize the array, it does not allocate nor initialize the individual strings (in the C version strings are just C strings that have to be allocated manually). You may want to check our samples (some of them allocate strings dynamically). That's why PnS crashes: your strings are basically random pointers to uninitialized memory.

[Minisonic]

I started out using the level meter example as a template and stripped it back to see what was causing the crash in my code. I’ll revisit it in the light of what you’ve said. Thanks.

[Blue Cat Audio]

The easiest way to handle strings is to use std::string objects (to handle the allocation) and only refer to their pointer using the c_str() method. Just make sure that these do not get reallocated during the lifetime of the script, as PnS expects unmutable strings with constant pointers, once the initialize function has been called.

[Minisonic]

Problem solved. I had a bool variable called "reset" and, although that doesn't bother Xcode, it seems to confuse PnS and cause a crash. Perhaps it thinks it's a pointer to a reset() function?

I renamed the variable and all seems to work as expected now.

[Blue Cat Audio]

reset is indeed a reserved function so using an exported symbol with the same can cause problems!

Code: Select all

 /** Reset the state of the filter.
  *
  */
  DSP_EXPORT void reset()
  {
  }