type spanSet struct {
	// A spanSet is a two-level data structure consisting of a
	// growable spine that points to fixed-sized blocks. The spine
	// can be accessed without locks, but adding a block or
	// growing it requires taking the spine lock.
	//
	// Because each mspan covers at least 8K of heap and takes at
	// most 8 bytes in the spanSet, the growth of the spine is
	// quite limited.
	//

         * than a handful of exceptions. But it seems prudent to set a cap on how many we'll cache.
         * This avoids out-of-control memory consumption, and it keeps the cache from growing so
         * large that doing the lookup is noticeably slower than redoing the work would be.
         *
         * Ideally we'd have a real eviction policy, but until we see a problem in practice, I hope

	//
	// Debuggers rely on us running on the same thread until we get to
	// dispatch the function they asked as to.
	//
	// We're going to transfer this to the new G we just created.
	lockOSThread()

	// Create a new goroutine to execute the call on. Run this on
	// the system stack to avoid growing our stack.
	systemstack(func() {
		// TODO(mknyszek): It would be nice to wrap these arguments in an allocated

         * than a handful of exceptions. But it seems prudent to set a cap on how many we'll cache.
         * This avoids out-of-control memory consumption, and it keeps the cache from growing so
         * large that doing the lookup is noticeably slower than redoing the work would be.
         *
         * Ideally we'd have a real eviction policy, but until we see a problem in practice, I hope

 *
 * This set also INTENTIONALLY ignores {@link Actions#doNothing()} actions and empty sets as to avoid growing for something that would never do anything.
 *
 * Actions are executed in order of insertion. Duplicates are ignored. Execution stops on the first failure.
 *

<2> The `app` subproject
<3> The `app` source code
<4> The `app` build script
<5> The optional settings file
=====

== Step 2. Add another Subproject to the Build
Imagine that our project is growing and requires a custom library to function.

Let's create this imaginary `lib`.
First, create a `lib` folder:

[source,text]
----
mkdir lib
----

[source,text]
----
cd lib
----

func FreeOSMemory() {
	freeOSMemory()
}

// SetMaxStack sets the maximum amount of memory that
// can be used by a single goroutine stack.
// If any goroutine exceeds this limit while growing its stack,
// the program crashes.
// SetMaxStack returns the previous setting.
// The initial setting is 1 GB on 64-bit systems, 250 MB on 32-bit systems.
// There may be a system-imposed maximum stack limit regardless

		err = regLoadMUIString(syscall.Handle(k), pname, &buf[0], uint32(len(buf)), &buflen, 0, pdir)
	}

	for err == syscall.ERROR_MORE_DATA { // Grow buffer if needed
		if buflen <= uint32(len(buf)) {
			break // Buffer not growing, assume race; break
		}
		buf = make([]uint16, buflen)
		err = regLoadMUIString(syscall.Handle(k), pname, &buf[0], uint32(len(buf)), &buflen, 0, pdir)
	}

	if err != nil {
		return "", err
	}

	// to be stack-allocated.
	for i := 0; i < 1; i++ {
		defer ap.method1()
	}
	defer ap.method2()
	defer ap.method1()
	ff1(ap, 1, 2, 3, 4, 5, 6, 7, 8, 9)
	// Try to get the stack to be moved by growing it too large, so
	// existing stack-allocated defer becomes invalid.
	rec1(2000)
}

func g3() {
	// Mix up the stack layout by adding in an extra function frame
	g2()
}

var globstruct struct {

			cleanup := setBits(bits)
			defer cleanup()

			b.StopTimer()
			x := New(data)
			size := testSaveRestore(nil, nil, x)       // verify correctness
			buf := bytes.NewBuffer(make([]byte, size)) // avoid growing
			b.SetBytes(int64(size))
			b.StartTimer()
			b.ReportAllocs()
			for i := 0; i < b.N; i++ {
				buf.Reset()
				if err := x.Write(buf); err != nil {
					b.Fatal(err)
				}
				var y Index