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I believe @dnfield already added an autorelease pool utility to the playground harness. Should we replace it with this new FML util? https://github.com/flutter/engine/pull/40748/files

It seems like we should have an autorelease pool drained after each test, instead of each test suite, no?

The test fixture class containing the autorelease pool will be instantiated separately for each test case.

Consider using this in https://github.com/flutter/engine/blob/main/impeller/playground/playground.cc#L265 as well. The feedback on that change was to move the class to FML.

Replaced the autorelease wrapper in Playground with fml::ScopedNSAutoreleasePool

Changed to the implementation based on objc_msgSend that had been used in Playground - PTAL

LGTM. I think this is needlessly convoluted in comparison to just using a .mm file but this will work.

This is specifically needed for TUs where you can't just use a .mm file - if you could you would just do @autoreleasepool {} :)

This is specifically needed for TUs where you can't just use a .mm file - if you could you would just do @autoreleasepool {} :)

You just compile the file you need depending on the platform. You can't use @autoreleasepool because the code where the scope of the pool isnt in objc++. Is there something I'm missing?

BUILD.gn

executable("fml") {
  source = ["autorelease_pool.h"]
  if (is_mac || is_ios) {
    sources += ["autorelease_pool_darwin.mm"]
  } else {
    # Add a stub if you don't want to conditionally include the header.
    sources += ["autorelease_pool_stub.cc"]
  }
}

autorelease_pool.h

class AutoreleasePool {
  private:
   void* pool_;
};

autorelease_pool_darwin.mm

AutoreleasePool::AutoreleasePool() {
  pool_ = [[NSAutoreleasePool alloc] init];
}

AutoreleasePool::~AutoreleasePool() {
  [pool_ drain];
}