477 lines
13 KiB
Plaintext
477 lines
13 KiB
Plaintext
// Copyright 2009 The Go 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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// See malloc.h for overview.
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//
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// TODO(rsc): double-check stats.
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package runtime
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#include <stddef.h>
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#include <errno.h>
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#include <stdlib.h>
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#include "go-alloc.h"
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#include "runtime.h"
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#include "malloc.h"
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#include "go-string.h"
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#include "interface.h"
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#include "go-type.h"
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typedef struct __go_empty_interface Eface;
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typedef struct __go_type_descriptor Type;
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typedef struct __go_func_type FuncType;
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MHeap runtime_mheap;
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extern MStats mstats; // defined in extern.go
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extern volatile int32 runtime_MemProfileRate
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__asm__ ("libgo_runtime.runtime.MemProfileRate");
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// Allocate an object of at least size bytes.
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// Small objects are allocated from the per-thread cache's free lists.
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// Large objects (> 32 kB) are allocated straight from the heap.
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void*
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runtime_mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
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{
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int32 sizeclass, rate;
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MCache *c;
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uintptr npages;
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MSpan *s;
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void *v;
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if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
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runtime_throw("malloc/free - deadlock");
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if(size == 0)
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size = 1;
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c = m->mcache;
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c->local_nmalloc++;
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if(size <= MaxSmallSize) {
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// Allocate from mcache free lists.
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sizeclass = runtime_SizeToClass(size);
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size = runtime_class_to_size[sizeclass];
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v = runtime_MCache_Alloc(c, sizeclass, size, zeroed);
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if(v == nil)
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runtime_throw("out of memory");
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c->local_alloc += size;
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c->local_total_alloc += size;
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c->local_by_size[sizeclass].nmalloc++;
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} else {
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// TODO(rsc): Report tracebacks for very large allocations.
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// Allocate directly from heap.
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npages = size >> PageShift;
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if((size & PageMask) != 0)
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npages++;
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s = runtime_MHeap_Alloc(&runtime_mheap, npages, 0, 1);
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if(s == nil)
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runtime_throw("out of memory");
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size = npages<<PageShift;
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c->local_alloc += size;
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c->local_total_alloc += size;
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v = (void*)(s->start << PageShift);
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// setup for mark sweep
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runtime_markspan(v, 0, 0, true);
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}
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if(!(flag & FlagNoGC))
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runtime_markallocated(v, size, (flag&FlagNoPointers) != 0);
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__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
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if(__sync_bool_compare_and_swap(&m->gcing, 1, 0)) {
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if(!(flag & FlagNoProfiling))
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__go_run_goroutine_gc(0);
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else {
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// We are being called from the profiler. Tell it
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// to invoke the garbage collector when it is
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// done. No need to use a sync function here.
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m->gcing_for_prof = 1;
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}
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}
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if(!(flag & FlagNoProfiling) && (rate = runtime_MemProfileRate) > 0) {
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if(size >= (uint32) rate)
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goto profile;
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if((uint32) m->mcache->next_sample > size)
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m->mcache->next_sample -= size;
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else {
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// pick next profile time
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if(rate > 0x3fffffff) // make 2*rate not overflow
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rate = 0x3fffffff;
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m->mcache->next_sample = runtime_fastrand1() % (2*rate);
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profile:
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runtime_setblockspecial(v);
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runtime_MProf_Malloc(v, size);
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}
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}
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if(dogc && mstats.heap_alloc >= mstats.next_gc)
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runtime_gc(0);
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return v;
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}
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void*
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__go_alloc(uintptr size)
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{
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return runtime_mallocgc(size, 0, 0, 1);
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}
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// Free the object whose base pointer is v.
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void
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__go_free(void *v)
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{
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int32 sizeclass;
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MSpan *s;
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MCache *c;
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uint32 prof;
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uintptr size;
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if(v == nil)
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return;
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// If you change this also change mgc0.c:/^sweepspan,
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// which has a copy of the guts of free.
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if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
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runtime_throw("malloc/free - deadlock");
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if(!runtime_mlookup(v, nil, nil, &s)) {
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// runtime_printf("free %p: not an allocated block\n", v);
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runtime_throw("free runtime_mlookup");
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}
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prof = runtime_blockspecial(v);
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// Find size class for v.
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sizeclass = s->sizeclass;
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c = m->mcache;
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if(sizeclass == 0) {
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// Large object.
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size = s->npages<<PageShift;
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*(uintptr*)(s->start<<PageShift) = 1; // mark as "needs to be zeroed"
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// Must mark v freed before calling unmarkspan and MHeap_Free:
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// they might coalesce v into other spans and change the bitmap further.
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runtime_markfreed(v, size);
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runtime_unmarkspan(v, 1<<PageShift);
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runtime_MHeap_Free(&runtime_mheap, s, 1);
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} else {
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// Small object.
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size = runtime_class_to_size[sizeclass];
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if(size > sizeof(uintptr))
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((uintptr*)v)[1] = 1; // mark as "needs to be zeroed"
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// Must mark v freed before calling MCache_Free:
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// it might coalesce v and other blocks into a bigger span
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// and change the bitmap further.
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runtime_markfreed(v, size);
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c->local_by_size[sizeclass].nfree++;
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runtime_MCache_Free(c, v, sizeclass, size);
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}
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c->local_alloc -= size;
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if(prof)
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runtime_MProf_Free(v, size);
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__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
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if(__sync_bool_compare_and_swap(&m->gcing, 1, 0))
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__go_run_goroutine_gc(1);
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}
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int32
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runtime_mlookup(void *v, byte **base, uintptr *size, MSpan **sp)
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{
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uintptr n, i;
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byte *p;
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MSpan *s;
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m->mcache->local_nlookup++;
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s = runtime_MHeap_LookupMaybe(&runtime_mheap, v);
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if(sp)
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*sp = s;
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if(s == nil) {
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runtime_checkfreed(v, 1);
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if(base)
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*base = nil;
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if(size)
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*size = 0;
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return 0;
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}
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p = (byte*)((uintptr)s->start<<PageShift);
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if(s->sizeclass == 0) {
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// Large object.
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if(base)
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*base = p;
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if(size)
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*size = s->npages<<PageShift;
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return 1;
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}
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if((byte*)v >= (byte*)s->limit) {
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// pointers past the last block do not count as pointers.
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return 0;
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}
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n = runtime_class_to_size[s->sizeclass];
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if(base) {
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i = ((byte*)v - p)/n;
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*base = p + i*n;
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}
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if(size)
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*size = n;
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return 1;
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}
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MCache*
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runtime_allocmcache(void)
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{
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MCache *c;
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if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
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runtime_throw("allocmcache - deadlock");
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runtime_lock(&runtime_mheap);
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c = runtime_FixAlloc_Alloc(&runtime_mheap.cachealloc);
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// Clear the free list used by FixAlloc; assume the rest is zeroed.
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c->list[0].list = nil;
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mstats.mcache_inuse = runtime_mheap.cachealloc.inuse;
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mstats.mcache_sys = runtime_mheap.cachealloc.sys;
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runtime_unlock(&runtime_mheap);
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__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
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if(__sync_bool_compare_and_swap(&m->gcing, 1, 0))
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__go_run_goroutine_gc(2);
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return c;
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}
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void
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runtime_purgecachedstats(M* m)
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{
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MCache *c;
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// Protected by either heap or GC lock.
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c = m->mcache;
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mstats.heap_alloc += c->local_cachealloc;
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c->local_cachealloc = 0;
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mstats.heap_objects += c->local_objects;
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c->local_objects = 0;
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mstats.nmalloc += c->local_nmalloc;
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c->local_nmalloc = 0;
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mstats.nfree += c->local_nfree;
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c->local_nfree = 0;
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mstats.nlookup += c->local_nlookup;
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c->local_nlookup = 0;
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mstats.alloc += c->local_alloc;
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c->local_alloc= 0;
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mstats.total_alloc += c->local_total_alloc;
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c->local_total_alloc= 0;
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}
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extern uintptr runtime_sizeof_C_MStats
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__asm__ ("libgo_runtime.runtime.Sizeof_C_MStats");
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#define MaxArena32 (2U<<30)
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void
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runtime_mallocinit(void)
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{
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byte *p;
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uintptr arena_size, bitmap_size;
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extern byte end[];
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runtime_sizeof_C_MStats = sizeof(MStats);
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runtime_InitSizes();
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// Set up the allocation arena, a contiguous area of memory where
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// allocated data will be found. The arena begins with a bitmap large
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// enough to hold 4 bits per allocated word.
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if(sizeof(void*) == 8) {
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// On a 64-bit machine, allocate from a single contiguous reservation.
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// 16 GB should be big enough for now.
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//
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// The code will work with the reservation at any address, but ask
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// SysReserve to use 0x000000f800000000 if possible.
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// Allocating a 16 GB region takes away 36 bits, and the amd64
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// doesn't let us choose the top 17 bits, so that leaves the 11 bits
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// in the middle of 0x00f8 for us to choose. Choosing 0x00f8 means
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// that the valid memory addresses will begin 0x00f8, 0x00f9, 0x00fa, 0x00fb.
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// None of the bytes f8 f9 fa fb can appear in valid UTF-8, and
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// they are otherwise as far from ff (likely a common byte) as possible.
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// Choosing 0x00 for the leading 6 bits was more arbitrary, but it
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// is not a common ASCII code point either. Using 0x11f8 instead
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// caused out of memory errors on OS X during thread allocations.
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// These choices are both for debuggability and to reduce the
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// odds of the conservative garbage collector not collecting memory
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// because some non-pointer block of memory had a bit pattern
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// that matched a memory address.
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//
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// Actually we reserve 17 GB (because the bitmap ends up being 1 GB)
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// but it hardly matters: fc is not valid UTF-8 either, and we have to
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// allocate 15 GB before we get that far.
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arena_size = (uintptr)(16LL<<30);
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bitmap_size = arena_size / (sizeof(void*)*8/4);
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p = runtime_SysReserve((void*)(0x00f8ULL<<32), bitmap_size + arena_size);
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if(p == nil)
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runtime_throw("runtime: cannot reserve arena virtual address space");
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} else {
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// On a 32-bit machine, we can't typically get away
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// with a giant virtual address space reservation.
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// Instead we map the memory information bitmap
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// immediately after the data segment, large enough
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// to handle another 2GB of mappings (256 MB),
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// along with a reservation for another 512 MB of memory.
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// When that gets used up, we'll start asking the kernel
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// for any memory anywhere and hope it's in the 2GB
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// following the bitmap (presumably the executable begins
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// near the bottom of memory, so we'll have to use up
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// most of memory before the kernel resorts to giving out
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// memory before the beginning of the text segment).
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//
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// Alternatively we could reserve 512 MB bitmap, enough
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// for 4GB of mappings, and then accept any memory the
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// kernel threw at us, but normally that's a waste of 512 MB
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// of address space, which is probably too much in a 32-bit world.
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bitmap_size = MaxArena32 / (sizeof(void*)*8/4);
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arena_size = 512<<20;
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// SysReserve treats the address we ask for, end, as a hint,
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// not as an absolute requirement. If we ask for the end
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// of the data segment but the operating system requires
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// a little more space before we can start allocating, it will
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// give out a slightly higher pointer. That's fine.
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// Run with what we get back.
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p = runtime_SysReserve(end, bitmap_size + arena_size);
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if(p == nil)
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runtime_throw("runtime: cannot reserve arena virtual address space");
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}
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if((uintptr)p & (((uintptr)1<<PageShift)-1))
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runtime_throw("runtime: SysReserve returned unaligned address");
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runtime_mheap.bitmap = p;
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runtime_mheap.arena_start = p + bitmap_size;
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runtime_mheap.arena_used = runtime_mheap.arena_start;
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runtime_mheap.arena_end = runtime_mheap.arena_start + arena_size;
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// Initialize the rest of the allocator.
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runtime_MHeap_Init(&runtime_mheap, runtime_SysAlloc);
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m->mcache = runtime_allocmcache();
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// Initialize malloc profiling.
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runtime_Mprof_Init();
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// Initialize finalizer.
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runtime_initfintab();
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// See if it works.
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runtime_free(runtime_malloc(1));
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}
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void*
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runtime_MHeap_SysAlloc(MHeap *h, uintptr n)
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{
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byte *p;
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if(n <= (uintptr)(h->arena_end - h->arena_used)) {
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// Keep taking from our reservation.
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p = h->arena_used;
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runtime_SysMap(p, n);
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h->arena_used += n;
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runtime_MHeap_MapBits(h);
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return p;
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}
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// On 64-bit, our reservation is all we have.
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if(sizeof(void*) == 8)
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return nil;
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// On 32-bit, once the reservation is gone we can
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// try to get memory at a location chosen by the OS
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// and hope that it is in the range we allocated bitmap for.
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p = runtime_SysAlloc(n);
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if(p == nil)
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return nil;
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if(p < h->arena_start || (uintptr)(p+n - h->arena_start) >= MaxArena32) {
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runtime_printf("runtime: memory allocated by OS not in usable range\n");
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runtime_SysFree(p, n);
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return nil;
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}
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if(p+n > h->arena_used) {
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h->arena_used = p+n;
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if(h->arena_used > h->arena_end)
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h->arena_end = h->arena_used;
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runtime_MHeap_MapBits(h);
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}
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return p;
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}
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// Runtime stubs.
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void*
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runtime_mal(uintptr n)
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{
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return runtime_mallocgc(n, 0, 1, 1);
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}
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func new(n uint32) (ret *uint8) {
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ret = runtime_mal(n);
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}
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func Alloc(n uintptr) (p *byte) {
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p = runtime_malloc(n);
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}
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func Free(p *byte) {
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runtime_free(p);
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}
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func Lookup(p *byte) (base *byte, size uintptr) {
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runtime_mlookup(p, &base, &size, nil);
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}
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func GC() {
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runtime_gc(1);
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}
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func SetFinalizer(obj Eface, finalizer Eface) {
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byte *base;
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uintptr size;
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const FuncType *ft;
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if(obj.__type_descriptor == nil) {
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// runtime_printf("runtime.SetFinalizer: first argument is nil interface\n");
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throw:
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runtime_throw("runtime.SetFinalizer");
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}
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if(obj.__type_descriptor->__code != GO_PTR) {
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// runtime_printf("runtime.SetFinalizer: first argument is %S, not pointer\n", *obj.type->string);
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goto throw;
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}
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if(!runtime_mlookup(obj.__object, &base, &size, nil) || obj.__object != base) {
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// runtime_printf("runtime.SetFinalizer: pointer not at beginning of allocated block\n");
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goto throw;
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}
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ft = nil;
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if(finalizer.__type_descriptor != nil) {
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if(finalizer.__type_descriptor->__code != GO_FUNC) {
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badfunc:
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// runtime_printf("runtime.SetFinalizer: second argument is %S, not func(%S)\n", *finalizer.type->string, *obj.type->string);
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goto throw;
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}
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ft = (const FuncType*)finalizer.__type_descriptor;
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if(ft->__dotdotdot || ft->__in.__count != 1 || !__go_type_descriptors_equal(*(Type**)ft->__in.__values, obj.__type_descriptor))
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goto badfunc;
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if(runtime_getfinalizer(obj.__object, 0)) {
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// runtime_printf("runtime.SetFinalizer: finalizer already set");
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goto throw;
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}
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}
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runtime_addfinalizer(obj.__object, finalizer.__type_descriptor != nil ? *(void**)finalizer.__object : nil, ft);
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}
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