escape.go

     1  // Copyright 2024 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package abi
     6  
     7  import "unsafe"
     8  
     9  // NoEscape hides the pointer p from escape analysis, preventing it
    10  // from escaping to the heap. It compiles down to nothing.
    11  //
    12  // WARNING: This is very subtle to use correctly. The caller must
    13  // ensure that it's truly safe for p to not escape to the heap by
    14  // maintaining runtime pointer invariants (for example, that globals
    15  // and the heap may not generally point into a stack).
    16  //
    17  //go:nosplit
    18  //go:nocheckptr
    19  func NoEscape(p unsafe.Pointer) unsafe.Pointer {
    20  	x := uintptr(p)
    21  	return unsafe.Pointer(x ^ 0)
    22  }
    23  
    24  var alwaysFalse bool
    25  var escapeSink any
    26  
    27  // Escape forces any pointers in x to escape to the heap.
    28  func Escape[T any](x T) T {
    29  	if alwaysFalse {
    30  		escapeSink = x
    31  	}
    32  	return x
    33  }
    34
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