// alternate signal stack. If the alternate signal stack is not set
// for the thread (the normal case) then set the alternate signal
// stack to the gsignal stack. If the alternate signal stack is set
// for the thread (the case when a non-Go thread sets the alternate
// signal stack and then calls a Go function) then set the gsignal
// stack to the alternate signal stack. We also set the alternate

// license that can be found in the LICENSE file.

// Trace stack table and acquisition.

package runtime

import (
	"internal/abi"
	"internal/goarch"
	"unsafe"
)

const (
	// Maximum number of PCs in a single stack trace.
	// Since events contain only stack id rather than whole stack trace,
	// we can allow quite large values here.
	traceStackSize = 128

}

type g struct {
	// Stack parameters.
	// stack describes the actual stack memory: [stack.lo, stack.hi).
	// stackguard0 is the stack pointer compared in the Go stack growth prologue.
	// It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption.
	// stackguard1 is the stack pointer compared in the //go:systemstack stack growth prologue.
	// It is stack.lo+StackGuard on g0 and gsignal stacks.

     *
     * @see Throwable#toString()
     */
    String getHeader();

    /**
     * Stack frames from the original exception.
     */
    List<StackTraceElement> getStackTrace();

    /**
     * Relevance of a given stack frame in the {@link #getStackTrace() stack trace}.
     */
    StackTraceRelevance getStackTraceRelevance(int frameIndex);

    /**

// stack.
//
// Synchronous safe-points are implemented by overloading the stack
// bound check in function prologues. To preempt a goroutine at the
// next synchronous safe-point, the runtime poisons the goroutine's
// stack bound to a value that will cause the next stack bound check
// to fail and enter the stack growth implementation, which will
// detect that it was actually a preemption and redirect to preemption
// handling.
//

	gs.augmentName(st.Stack)

	// Handle the goroutine state transition.
	from, to := st.Goroutine()
	if from == to {
		// Filter out no-op events.
		return
	}
	if from.Executing() && !to.Executing() {
		if to == trace.GoWaiting {
			// Goroutine started blocking.
			gs.block(ev.Time(), ev.Stack(), st.Reason, ctx)
		} else {
			gs.stop(ev.Time(), ev.Stack(), ctx)
		}
	}

//
// This must be deeply nosplit because it is called from a function
// prologue before the stack is set up and because the compiler will
// call it from any splittable prologue (leading to infinite
// recursion).
//
// Ideally it should also use very little stack because the linker
// doesn't currently account for this in nosplit stack depth checking.
//
// Ensure mayMoreStackPreempt can be called for all ABIs.
//
//go:nosplit

            startPos = 0;
            endPos = stack.size();
        } else {
            // When analysing a problem stack trace, consider only the deepest user code in the stack.
            startPos = failure.indexOfStackFrame(0, StackFramePredicate.USER_CODE);
            if (startPos == -1) {
                // No user code in the stack
                return null;
            }

	}

	var state stackScanState
	state.stack = gp.stack

	if stackTraceDebug {
		println("stack trace goroutine", gp.goid)
	}

	if debugScanConservative && gp.asyncSafePoint {
		print("scanning async preempted goroutine ", gp.goid, " stack [", hex(gp.stack.lo), ",", hex(gp.stack.hi), ")\n")
	}

	// Scan the saved context register. This is effectively a live
	// register that gets moved back and forth between the

// A StackRecord describes a single execution stack.
type StackRecord struct {
	Stack0 [32]uintptr // stack trace for this record; ends at first 0 entry
}

// Stack returns the stack trace associated with the record,
// a prefix of r.Stack0.
func (r *StackRecord) Stack() []uintptr {
	for i, v := range r.Stack0 {
		if v == 0 {
			return r.Stack0[0:i]
		}
	}
	return r.Stack0[0:]
}