mirror of
https://github.com/tinygo-org/tinygo.git
synced 2026-08-05 03:27:48 +00:00
Ayke van Laethem
5404c81ffd
Scan globals conservatively by reading writable sections from the PE header. I'd like to get rid of needing to precisely scan globals eventually, and this brings us one step closer. It also avoids a bug with ThinLTO on Windows.
85 lines
2.0 KiB
Go
85 lines
2.0 KiB
Go
//go:build gc.leaking
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// +build gc.leaking
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package runtime
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// This GC implementation is the simplest useful memory allocator possible: it
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// only allocates memory and never frees it. For some constrained systems, it
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// may be the only memory allocator possible.
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import (
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"unsafe"
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)
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const gcAsserts = false // perform sanity checks
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// Ever-incrementing pointer: no memory is freed.
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var heapptr = heapStart
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// Inlining alloc() speeds things up slightly but bloats the executable by 50%,
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// see https://github.com/tinygo-org/tinygo/issues/2674. So don't.
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//go:noinline
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func alloc(size uintptr, layout unsafe.Pointer) unsafe.Pointer {
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// TODO: this can be optimized by not casting between pointers and ints so
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// much. And by using platform-native data types (e.g. *uint8 for 8-bit
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// systems).
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size = align(size)
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addr := heapptr
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heapptr += size
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for heapptr >= heapEnd {
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// Try to increase the heap and check again.
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if growHeap() {
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continue
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}
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// Failed to make the heap bigger, so we must really be out of memory.
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runtimePanic("out of memory")
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}
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pointer := unsafe.Pointer(addr)
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memzero(pointer, size)
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return pointer
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}
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func realloc(ptr unsafe.Pointer, size uintptr) unsafe.Pointer {
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newAlloc := alloc(size, nil)
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if ptr == nil {
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return newAlloc
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}
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// according to POSIX everything beyond the previous pointer's
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// size will have indeterminate values so we can just copy garbage
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memcpy(newAlloc, ptr, size)
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return newAlloc
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}
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func free(ptr unsafe.Pointer) {
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// Memory is never freed.
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}
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func GC() {
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// No-op.
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}
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func KeepAlive(x interface{}) {
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// Unimplemented. Only required with SetFinalizer().
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}
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func SetFinalizer(obj interface{}, finalizer interface{}) {
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// Unimplemented.
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}
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func initHeap() {
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// preinit() may have moved heapStart; reset heapptr
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heapptr = heapStart
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}
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// setHeapEnd sets a new (larger) heapEnd pointer.
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func setHeapEnd(newHeapEnd uintptr) {
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// This "heap" is so simple that simply assigning a new value is good
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// enough.
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heapEnd = newHeapEnd
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}
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func markRoots(start, end uintptr) {
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// dummy, so that markGlobals will compile
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}
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