306 lines
6.9 KiB
Go
306 lines
6.9 KiB
Go
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// Copyright 2023 The Libc Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build libc.membrk && !libc.memgrind && linux && (amd64 || loong64)
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// This is a debug-only version of the memory handling functions. When a
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// program is built with -tags=libc.membrk a simple but safe version of malloc
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// and friends is used that works like sbrk(2). Additionally free becomes a
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// nop.
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// The fixed heap is initially filled with random bytes from a full cycle PRNG,
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// program startup time is substantially prolonged.
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package libc // import "modernc.org/libc/v2"
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import (
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"fmt"
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"math"
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"math/bits"
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"runtime"
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"strings"
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"time"
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"unsafe"
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"modernc.org/mathutil"
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)
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const (
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isMemBrk = true
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heapSize = 1 << 30
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)
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var (
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brkIndex uintptr
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heap [heapSize]byte
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heapP uintptr
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heap0 uintptr
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heapRecords []heapRecord
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heapUsable = map[uintptr]Tsize_t{}
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heapFree = map[uintptr]struct{}{}
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rng *mathutil.FC32
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)
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type heapRecord struct {
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p uintptr
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pc uintptr
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}
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func (r *heapRecord) String() string {
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return fmt.Sprintf("[p=%#0x usable=%v pc=%s]", r.p, Xmalloc_usable_size(nil, r.p), pc2origin(r.pc))
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}
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func init() {
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if roundup(heapGuard, heapAlign) != heapGuard {
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panic("internal error")
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}
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heap0 = uintptr(unsafe.Pointer(&heap[0]))
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heapP = roundup(heap0, heapAlign)
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var err error
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if rng, err = mathutil.NewFC32(math.MinInt32, math.MaxInt32, true); err != nil {
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panic(err)
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}
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rng.Seed(time.Now().UnixNano())
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for i := range heap {
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heap[i] = byte(rng.Next())
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}
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}
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func pc2origin(pc uintptr) string {
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f := runtime.FuncForPC(pc)
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var fn, fns string
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var fl int
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if f != nil {
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fn, fl = f.FileLine(pc)
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fns = f.Name()
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if x := strings.LastIndex(fns, "."); x > 0 {
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fns = fns[x+1:]
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}
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}
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return fmt.Sprintf("%s:%d:%s", fn, fl, fns)
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}
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func malloc0(tls *TLS, pc uintptr, n0 Tsize_t, zero bool) (r uintptr) {
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usable := roundup(uintptr(n0), heapAlign)
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rq := usable + 2*heapGuard
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if brkIndex+rq > uintptr(len(heap)) {
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tls.setErrno(ENOMEM)
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return 0
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}
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r, brkIndex = heapP+brkIndex, brkIndex+rq
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heapRecords = append(heapRecords, heapRecord{p: r, pc: pc})
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r += heapGuard
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heapUsable[r] = Tsize_t(usable)
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if zero {
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n := uintptr(n0)
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for i := uintptr(0); i < n; i++ {
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*(*byte)(unsafe.Pointer(r + i)) = 0
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}
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}
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return r
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}
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func Xmalloc(tls *TLS, n Tsize_t) (r uintptr) {
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if __ccgo_strace {
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trc("tls=%v n=%v, (%v:)", tls, n, origin(2))
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defer func() { trc("-> %v", r) }()
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}
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if n > math.MaxInt {
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tls.setErrno(ENOMEM)
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return 0
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}
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if n == 0 {
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// malloc(0) should return unique pointers
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// (often expected and gnulib replaces malloc if malloc(0) returns 0)
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n = 1
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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pc, _, _, _ := runtime.Caller(1)
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return malloc0(tls, pc, n, false)
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}
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func Xcalloc(tls *TLS, m Tsize_t, n Tsize_t) (r uintptr) {
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if __ccgo_strace {
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trc("tls=%v m=%v n=%v, (%v:)", tls, m, n, origin(2))
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defer func() { trc("-> %v", r) }()
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}
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hi, rq := bits.Mul(uint(m), uint(n))
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if hi != 0 || rq > math.MaxInt {
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tls.setErrno(ENOMEM)
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return 0
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}
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if rq == 0 {
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rq = 1
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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pc, _, _, _ := runtime.Caller(1)
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return malloc0(tls, pc, Tsize_t(rq), true)
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}
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func Xrealloc(tls *TLS, p uintptr, n Tsize_t) (r uintptr) {
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if __ccgo_strace {
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trc("tls=%v p=%v n=%v, (%v:)", tls, p, n, origin(2))
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defer func() { trc("-> %v", r) }()
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}
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if n == 0 {
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Xfree(tls, p)
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return 0
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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pc, _, _, _ := runtime.Caller(1)
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if p == 0 {
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return malloc0(tls, pc, n, false)
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}
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usable := heapUsable[p]
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if usable == 0 {
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panic(todo("realloc of unallocated memory: %#0x", p))
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}
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if usable >= n { // in place
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return p
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}
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// malloc
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r = malloc0(tls, pc, n, false)
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copy(unsafe.Slice((*byte)(unsafe.Pointer(r)), usable), unsafe.Slice((*byte)(unsafe.Pointer(p)), usable))
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Xfree(tls, p)
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return r
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}
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func Xfree(tls *TLS, p uintptr) {
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if __ccgo_strace {
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trc("tls=%v p=%v, (%v:)", tls, p, origin(2))
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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if p == 0 {
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return
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}
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if _, ok := heapUsable[p]; !ok {
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panic(todo("free of unallocated memory: %#0x", p))
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}
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if _, ok := heapFree[p]; ok {
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panic(todo("double free: %#0x", p))
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}
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heapFree[p] = struct{}{}
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}
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func Xmalloc_usable_size(tls *TLS, p uintptr) (r Tsize_t) {
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if __ccgo_strace {
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trc("tls=%v p=%v, (%v:)", tls, p, origin(2))
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defer func() { trc("-> %v", r) }()
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}
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if p == 0 {
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return 0
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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return heapUsable[p]
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}
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func MemAudit() (r []*MemAuditError) {
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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a := heapRecords
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auditP := heap0
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rng.Seek(0)
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for _, v := range a {
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heapP := v.p
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mallocP := heapP + heapGuard
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usable := heapUsable[mallocP]
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for ; auditP < mallocP; auditP++ {
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if g, e := *(*byte)(unsafe.Pointer(auditP)), byte(rng.Next()); g != e {
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r = append(r, &MemAuditError{Caller: pc2origin(v.pc), Message: fmt.Sprintf("guard area before %#0x, %v is corrupted at %#0x, got %#02x, expected %#02x", mallocP, usable, auditP, g, e)})
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}
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}
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for i := 0; Tsize_t(i) < usable; i++ {
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rng.Next()
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}
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auditP = mallocP + uintptr(usable)
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z := roundup(auditP, heapAlign)
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z += heapGuard
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for ; auditP < z; auditP++ {
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if g, e := *(*byte)(unsafe.Pointer(auditP)), byte(rng.Next()); g != e {
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r = append(r, &MemAuditError{Caller: pc2origin(v.pc), Message: fmt.Sprintf("guard area after %#0x, %v is corrupted at %#0x, got %#02x, expected %#02x", mallocP, usable, auditP, g, e)})
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}
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}
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}
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z := heap0 + uintptr(len(heap))
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for ; auditP < z; auditP++ {
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if g, e := *(*byte)(unsafe.Pointer(auditP)), byte(rng.Next()); g != e {
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r = append(r, &MemAuditError{Caller: "-", Message: fmt.Sprintf("guard area after used heap is corrupted at %#0x, got %#02x, expected %#02x", auditP, g, e)})
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return r // Report only the first fail
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}
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}
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return r
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}
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func UsableSize(p uintptr) Tsize_t {
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if p == 0 {
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return 0
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}
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allocatorMu.Lock()
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defer allocatorMu.Unlock()
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return heapUsable[p]
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}
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// MemAuditStart locks the memory allocator, initializes and enables memory
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// auditing. Finaly it unlocks the memory allocator.
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//
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// Some memory handling errors, like double free or freeing of unallocated
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// memory, will panic when memory auditing is enabled.
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//
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// This memory auditing functionality has to be enabled using the libc.memgrind
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// build tag.
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//
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// It is intended only for debug/test builds. It slows down memory allocation
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// routines and it has additional memory costs.
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func MemAuditStart() {}
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// MemAuditReport locks the memory allocator, reports memory leaks, if any.
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// Finally it disables memory auditing and unlocks the memory allocator.
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//
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// This memory auditing functionality has to be enabled using the libc.memgrind
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// build tag.
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//
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// It is intended only for debug/test builds. It slows down memory allocation
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// routines and it has additional memory costs.
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func MemAuditReport() error { return nil }
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