length:        50,
			checker: func(t *testing.T, c []gcCycleResult) {
				n := len(c)
				if n > 4 {
					// After the 4th GC, the heap will stop growing.
					// First, let's make sure we're finishing near the goal, with some extra
					// room because we're probably going to be triggering early.
					assertInRange(t, "goal ratio", c[n-1].goalRatio(), 0.925, 1.025)

		pc--
	}
	return isAbortPC(pc)
}

// isgoexception reports whether this exception should be translated
// into a Go panic or throw.
//
// It is nosplit to avoid growing the stack in case we're aborting
// because of a stack overflow.
//
//go:nosplit
func isgoexception(info *exceptionrecord, r *context) bool {
	// Only handle exception if executing instructions in Go binary

	inuse := int64(s1.StackInuse) - int64(s0.StackInuse)
	t.Logf("Inuse %vMB for stack mem", inuse>>20)
	if inuse > 4<<20 {
		t.Fatalf("Stack inuse: want %v, got %v", 4<<20, inuse)
	}
}

// Test stack growing in different contexts.
func TestStackGrowth(t *testing.T) {
	if *flagQuick {
		t.Skip("-quick")
	}

	var wg sync.WaitGroup

	// in a normal goroutine
	var growDuration time.Duration // For debugging failures

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