purego: remove pooling of syscall (#452)

func.go

@@ -10,7 +10,6 @@ import (
 	"math"
 	"reflect"
 	"runtime"
-	"sync"
 	"unsafe"
 
 	"github.com/ebitengine/purego/internal/strings"
@@ -22,10 +21,6 @@ const (
 	align8ByteSize = 8 // 8-byte alignment boundary
 )
 
-var thePool = sync.Pool{New: func() any {
-	return new(syscall15Args)
-}}
-
 // RegisterLibFunc is a wrapper around RegisterFunc that uses the C function returned from Dlsym(handle, name).
 // It panics if it can't find the name symbol.
 func RegisterLibFunc(fptr any, handle uintptr, name string) {
@@ -310,8 +305,7 @@ func RegisterFunc(fptr any, cfn uintptr) {
 			keepAlive = addValue(v, keepAlive, addInt, addFloat, addStack, &numInts, &numFloats, &numStack)
 		}
 
-		syscall := thePool.Get().(*syscall15Args)
-		defer thePool.Put(syscall)
+		syscall := &syscall15Args{}
 
 		if runtime.GOARCH == "loong64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "riscv64" || runtime.GOARCH == "s390x" {
 			syscall.Set(cfn, sysargs[:], floats[:], 0)
@@ -321,7 +315,6 @@ func RegisterFunc(fptr any, cfn uintptr) {
 			syscall.Set(cfn, sysargs[:], floats[:], arm64_r8)
 			runtime_cgocall(syscall15XABI0, unsafe.Pointer(syscall))
 		} else {
-			*syscall = syscall15Args{}
 			// This is a fallback for Windows amd64, 386, and arm. Note this may not support floats
 			syscall.a1, syscall.a2, _ = syscall_syscall15X(cfn, sysargs[0], sysargs[1], sysargs[2], sysargs[3], sysargs[4],
 				sysargs[5], sysargs[6], sysargs[7], sysargs[8], sysargs[9], sysargs[10], sysargs[11],

func_test.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 	"testing"
 	"unsafe"
 
@@ -35,6 +36,40 @@ func getSystemLibrary() (string, error) {
 	}
 }
 
+func TestRegisterFunc_ConcurrentPointerReturn(t *testing.T) {
+	library, err := getSystemLibrary()
+	if err != nil {
+		t.Fatalf("couldn't get system library: %s", err)
+	}
+	libc, err := load.OpenLibrary(library)
+	if err != nil {
+		t.Fatalf("failed to dlopen: %s", err)
+	}
+
+	var alloc func(uint64) *byte
+	var free func(*byte)
+	purego.RegisterLibFunc(&alloc, libc, "malloc")
+	purego.RegisterLibFunc(&free, libc, "free")
+
+	var wg sync.WaitGroup
+
+	for i := 0; i < runtime.NumCPU(); i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < 400_000; j++ {
+				ptr := alloc(5)
+				if ptr == nil {
+					continue
+				}
+				free(ptr)
+			}
+		}(i)
+	}
+
+	wg.Wait()
+}
+
 func TestRegisterFunc(t *testing.T) {
 	library, err := getSystemLibrary()
 	if err != nil {

syscall_sysv.go

@@ -16,10 +16,7 @@ import (
 var syscall15XABI0 uintptr
 
 func syscall_syscall15X(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2, err uintptr) {
-	args := thePool.Get().(*syscall15Args)
-	defer thePool.Put(args)
-
-	*args = syscall15Args{
+	args := &syscall15Args{
 		fn: fn,
 		a1: a1, a2: a2, a3: a3, a4: a4, a5: a5, a6: a6, a7: a7, a8: a8,
 		a9: a9, a10: a10, a11: a11, a12: a12, a13: a13, a14: a14, a15: a15,