Allow custom wasm malloc implementation (#3245)

Author: anuraaga

src/runtime/arch_tinygowasm.go

@@ -88,55 +88,3 @@ func growHeap() bool {
 	// Heap has grown successfully.
 	return true
 }
-
-// The below functions override the default allocator of wasi-libc. This ensures
-// code linked from other languages can allocate memory without colliding with
-// our GC allocations.
-
-var allocs = make(map[uintptr][]byte)
-
-//export malloc
-func libc_malloc(size uintptr) unsafe.Pointer {
-	buf := make([]byte, size)
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
-	return ptr
-}
-
-//export free
-func libc_free(ptr unsafe.Pointer) {
-	if ptr == nil {
-		return
-	}
-	if _, ok := allocs[uintptr(ptr)]; ok {
-		delete(allocs, uintptr(ptr))
-	} else {
-		panic("free: invalid pointer")
-	}
-}
-
-//export calloc
-func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
-	// No difference between calloc and malloc.
-	return libc_malloc(nmemb * size)
-}
-
-//export realloc
-func libc_realloc(oldPtr unsafe.Pointer, size uintptr) unsafe.Pointer {
-	// It's hard to optimize this to expand the current buffer with our GC, but
-	// it is theoretically possible. For now, just always allocate fresh.
-	buf := make([]byte, size)
-
-	if oldPtr != nil {
-		if oldBuf, ok := allocs[uintptr(oldPtr)]; ok {
-			copy(buf, oldBuf)
-			delete(allocs, uintptr(oldPtr))
-		} else {
-			panic("realloc: invalid pointer")
-		}
-	}
-
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
-	return ptr
-}

src/runtime/arch_tinygowasm_malloc.go

@@ -0,0 +1,58 @@
+//go:build tinygo.wasm && !custommalloc
+// +build tinygo.wasm,!custommalloc
+
+package runtime
+
+import "unsafe"
+
+// The below functions override the default allocator of wasi-libc. This ensures
+// code linked from other languages can allocate memory without colliding with
+// our GC allocations.
+
+var allocs = make(map[uintptr][]byte)
+
+//export malloc
+func libc_malloc(size uintptr) unsafe.Pointer {
+	buf := make([]byte, size)
+	ptr := unsafe.Pointer(&buf[0])
+	allocs[uintptr(ptr)] = buf
+	return ptr
+}
+
+//export free
+func libc_free(ptr unsafe.Pointer) {
+	if ptr == nil {
+		return
+	}
+	if _, ok := allocs[uintptr(ptr)]; ok {
+		delete(allocs, uintptr(ptr))
+	} else {
+		panic("free: invalid pointer")
+	}
+}
+
+//export calloc
+func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
+	// No difference between calloc and malloc.
+	return libc_malloc(nmemb * size)
+}
+
+//export realloc
+func libc_realloc(oldPtr unsafe.Pointer, size uintptr) unsafe.Pointer {
+	// It's hard to optimize this to expand the current buffer with our GC, but
+	// it is theoretically possible. For now, just always allocate fresh.
+	buf := make([]byte, size)
+
+	if oldPtr != nil {
+		if oldBuf, ok := allocs[uintptr(oldPtr)]; ok {
+			copy(buf, oldBuf)
+			delete(allocs, uintptr(oldPtr))
+		} else {
+			panic("realloc: invalid pointer")
+		}
+	}
+
+	ptr := unsafe.Pointer(&buf[0])
+	allocs[uintptr(ptr)] = buf
+	return ptr
+}