// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import 

func ( unsafe.Pointer,  *_type,  uintptr) {
	// nil pointer is always suitably aligned (#47430).
	if  == nil {
		return
	}

	// Check that (*[n]elem)(p) is appropriately aligned.
	// Note that we allow unaligned pointers if the types they point to contain
	// no pointers themselves. See issue 37298.
	// TODO(mdempsky): What about fieldAlign?
	if .PtrBytes != 0 && uintptr()&(uintptr(.Align_)-1) != 0 {
		throw("checkptr: misaligned pointer conversion")
	}

	// Check that (*[n]elem)(p) doesn't straddle multiple heap objects.
	// TODO(mdempsky): Fix #46938 so we don't need to worry about overflow here.
	if checkptrStraddles(, *.Size_) {
		throw("checkptr: converted pointer straddles multiple allocations")
	}
}

// checkptrStraddles reports whether the first size-bytes of memory
// addressed by ptr is known to straddle more than one Go allocation.
func ( unsafe.Pointer,  uintptr) bool {
	if  <= 1 {
		return false
	}

	// Check that add(ptr, size-1) won't overflow. This avoids the risk
	// of producing an illegal pointer value (assuming ptr is legal).
	if uintptr() >= -( - 1) {
		return true
	}
	 := add(, -1)

	// TODO(mdempsky): Detect when [ptr, end] contains Go allocations,
	// but neither ptr nor end point into one themselves.

	return checkptrBase() != checkptrBase()
}

func ( unsafe.Pointer,  []unsafe.Pointer) {
	if 0 < uintptr() && uintptr() < minLegalPointer {
		throw("checkptr: pointer arithmetic computed bad pointer value")
	}

	// Check that if the computed pointer p points into a heap
	// object, then one of the original pointers must have pointed
	// into the same object.
	 := checkptrBase()
	if  == 0 {
		return
	}

	for ,  := range  {
		if  == checkptrBase() {
			return
		}
	}

	throw("checkptr: pointer arithmetic result points to invalid allocation")
}

// checkptrBase returns the base address for the allocation containing
// the address p.
//
// Importantly, if p1 and p2 point into the same variable, then
// checkptrBase(p1) == checkptrBase(p2). However, the converse/inverse
// is not necessarily true as allocations can have trailing padding,
// and multiple variables may be packed into a single allocation.
func ( unsafe.Pointer) uintptr {
	// stack
	if  := getg(); .stack.lo <= uintptr() && uintptr() < .stack.hi {
		// TODO(mdempsky): Walk the stack to identify the
		// specific stack frame or even stack object that p
		// points into.
		//
		// In the mean time, use "1" as a pseudo-address to
		// represent the stack. This is an invalid address on
		// all platforms, so it's guaranteed to be distinct
		// from any of the addresses we might return below.
		return 1
	}

	// heap (must check after stack because of #35068)
	if , ,  := findObject(uintptr(), 0, 0);  != 0 {
		return 
	}

	// data or bss
	for ,  := range activeModules() {
		if .data <= uintptr() && uintptr() < .edata {
			return .data
		}
		if .bss <= uintptr() && uintptr() < .ebss {
			return .bss
		}
	}

	return 0
}