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//go:build gc.leaking
package runtime
// This GC implementation is the simplest useful memory allocator possible: it
// only allocates memory and never frees it. For some constrained systems, it
// may be the only memory allocator possible.
import (
"unsafe"
)
// Ever-incrementing pointer: no memory is freed.
var heapptr = heapStart
// Total amount allocated for runtime.MemStats
var gcTotalAlloc uint64
// Total number of calls to alloc()
var gcMallocs uint64
// Total number of objected freed; for leaking collector this stays 0
const gcFrees = 0
// Inlining alloc() speeds things up slightly but bloats the executable by 50%,
// see https://github.com/tinygo-org/tinygo/issues/2674. So don't.
//
//go:noinline
func alloc(size uintptr, layout unsafe.Pointer) unsafe.Pointer {
// TODO: this can be optimized by not casting between pointers and ints so
// much. And by using platform-native data types (e.g. *uint8 for 8-bit
// systems).
size = align(size)
addr := heapptr
gcTotalAlloc += uint64(size)
gcMallocs++
heapptr += size
for heapptr >= heapEnd {
// Try to increase the heap and check again.
if growHeap() {
continue
}
// Failed to make the heap bigger, so we must really be out of memory.
runtimePanic("out of memory")
}
pointer := unsafe.Pointer(addr)
zero_new_alloc(pointer, size)
return pointer
}
func realloc(ptr unsafe.Pointer, size uintptr) unsafe.Pointer {
newAlloc := alloc(size, nil)
if ptr == nil {
return newAlloc
}
// according to POSIX everything beyond the previous pointer's
// size will have indeterminate values so we can just copy garbage
memcpy(newAlloc, ptr, size)
return newAlloc
}
func free(ptr unsafe.Pointer) {
// Memory is never freed.
}
// ReadMemStats populates m with memory statistics.
//
// The returned memory statistics are up to date as of the
// call to ReadMemStats. This would not do GC implicitly for you.
func ReadMemStats(m *MemStats) {
m.HeapIdle = 0
m.HeapInuse = gcTotalAlloc
m.HeapReleased = 0 // always 0, we don't currently release memory back to the OS.
m.HeapSys = m.HeapInuse + m.HeapIdle
m.GCSys = 0
m.TotalAlloc = gcTotalAlloc
m.Mallocs = gcMallocs
m.Frees = gcFrees
m.Sys = uint64(heapEnd - heapStart)
// no free -- current in use heap is the total allocated
m.HeapAlloc = gcTotalAlloc
m.Alloc = m.HeapAlloc
}
func GC() {
// No-op.
}
func SetFinalizer(obj interface{}, finalizer interface{}) {
// No-op.
}
func initHeap() {
// preinit() may have moved heapStart; reset heapptr
heapptr = heapStart
}
// setHeapEnd sets a new (larger) heapEnd pointer.
func setHeapEnd(newHeapEnd uintptr) {
// This "heap" is so simple that simply assigning a new value is good
// enough.
heapEnd = newHeapEnd
}
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