// The WriteCloser's Close method must be used to flush pending data to w.
// The Compressor itself must be safe to invoke from multiple goroutines
// simultaneously, but each returned writer will be used only by
// one goroutine at a time.
type Compressor func(w io.Writer) (io.WriteCloser, error)

// A Decompressor returns a new decompressing reader, reading from r.

Some, such as atomic compare-and-swap, are both read-like and write-like.
</p>

<p>
A <i>goroutine execution</i> is modeled as a set of memory operations executed by a single goroutine.
</p>

<p>
<b>Requirement 1</b>:
The memory operations in each goroutine must correspond to a correct sequential execution of that goroutine,
given the values read from and written to memory.

// panicking goroutine. Executing a call to recover inside a deferred
// function (but not any function called by it) stops the panicking sequence
// by restoring normal execution and retrieves the error value passed to the
// call of panic. If recover is called outside the deferred function it will
// not stop a panicking sequence. In this case, or when the goroutine is not
// panicking, recover returns nil.
//

	neededFrags = make(map[urlFrag][]string) // URL#frag -> who needs it
)

var aRx = regexp.MustCompile(`<a href=['"]?(/[^\s'">]+)`)

// Owned by crawlLoop goroutine:
var (
	linkSources = make(map[string][]string) // url no fragment -> sources
	fragExists  = make(map[urlFrag]bool)
	problems    []string
)

func localLinks(body string) (links []string) {

					// may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
					// function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
					// This changes the SP, thus we have to update the SP used by the imported function.

					// func wasmExit(code int32)

<p>
The function value and parameters are
<a href="#Calls">evaluated as usual</a>
in the calling goroutine, but
unlike with a regular call, program execution does not wait
for the invoked function to complete.
Instead, the function begins executing independently
in a new goroutine.
When the function terminates, its goroutine also terminates.
If the function has any return values, they are discarded when the
function completes.

		}
	}()
	C.callPanic()
}

// Test that C code can return a value if it calls a Go function that
// causes a stack copy.
func testReturnAfterGrow(t *testing.T) {
	// Use a new goroutine so that we get a small stack.
	c := make(chan int)
	go func() {
		c <- int(C.returnAfterGrow())
	}()
	if got, want := <-c, 123456; got != want {
		t.Errorf("got %d want %d", got, want)
	}
}

</p>

<h3 id="arm">ARM</h3>

<p>
The registers <code>R10</code> and <code>R11</code>
are reserved by the compiler and linker.
</p>

<p>
<code>R10</code> points to the <code>g</code> (goroutine) structure.
Within assembler source code, this pointer must be referred to as <code>g</code>;
the name <code>R10</code> is not recognized.
</p>

<p>

<p>
The function value and parameters are
<a href="#Calls">evaluated as usual</a>
in the calling goroutine, but
unlike with a regular call, program execution does not wait
for the invoked function to complete.
Instead, the function begins executing independently
in a new goroutine.
When the function terminates, its goroutine also terminates.
If the function has any return values, they are discarded when the
function completes.

// it is no longer referenced, so it must be kept alive (see runtime.KeepAlive)
// until any memory allocated from it is no longer needed.
//
// An Arena must never be used concurrently by multiple goroutines.
type Arena struct {
	a unsafe.Pointer
}

// NewArena allocates a new arena.
func NewArena() *Arena {
	return &Arena{a: runtime_arena_newArena()}
}