windows/mkwinsyscall: use syscall.SyscallN instead of syscall.Syscall{6,9,12,15}

Replace syscall.Syscall6, Syscall9, Syscall12, and Syscall15 with syscall.SyscallN for Go 1.18+. This simplifies system calls by allowing the exact number of arguments needed, eliminating zero padding and reducing potential errors.

Updated TestSyscallXGeneration to TestSyscallNGeneration to verify correct SyscallN generation for different argument counts.

Change-Id: Icd6662b591d7548e367b88f34243f5529e177eab
GitHub-Last-Rev: c06fca1
GitHub-Pull-Request: #219
Reviewed-on: https://go-review.googlesource.com/c/sys/+/614082
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Alex Brainman <[email protected]>
Reviewed-by: Quim Muntal <[email protected]>

Author: mertakman

windows/mkwinsyscall/mkwinsyscall.go

@@ -62,7 +62,6 @@ import (
 	"path/filepath"
 	"runtime"
 	"sort"
-	"strconv"
 	"strings"
 	"text/template"
 )
@@ -543,47 +542,9 @@ func (f *Fn) ParamPrintList() string {
 	return join(f.Params, func(p *Param) string { return fmt.Sprintf(`"%s=", %s, `, p.Name, p.Name) }, `", ", `)
 }
 
-// ParamCount return number of syscall parameters for function f.
-func (f *Fn) ParamCount() int {
-	n := 0
-	for _, p := range f.Params {
-		n += len(p.SyscallArgList())
-	}
-	return n
-}
-
-// SyscallParamCount determines which version of Syscall/Syscall6/Syscall9/...
-// to use. It returns parameter count for correspondent SyscallX function.
-func (f *Fn) SyscallParamCount() int {
-	n := f.ParamCount()
-	switch {
-	case n <= 3:
-		return 3
-	case n <= 6:
-		return 6
-	case n <= 9:
-		return 9
-	case n <= 12:
-		return 12
-	case n <= 15:
-		return 15
-	case n <= 42: // current SyscallN limit
-		return n
-	default:
-		panic("too many arguments to system call")
-	}
-}
-
-// Syscall determines which SyscallX function to use for function f.
-func (f *Fn) Syscall() string {
-	c := f.SyscallParamCount()
-	if c == 3 {
-		return syscalldot() + "Syscall"
-	}
-	if c > 15 {
-		return syscalldot() + "SyscallN"
-	}
-	return syscalldot() + "Syscall" + strconv.Itoa(c)
+// SyscallN returns a string representing the SyscallN function.
+func (f *Fn) SyscallN() string {
+	return syscalldot() + "SyscallN"
 }
 
 // SyscallParamList returns source code for SyscallX parameters for function f.
@@ -592,9 +553,12 @@ func (f *Fn) SyscallParamList() string {
 	for _, p := range f.Params {
 		a = append(a, p.SyscallArgList()...)
 	}
-	for len(a) < f.SyscallParamCount() {
-		a = append(a, "0")
+
+	// Check if the number exceeds the current SyscallN limit
+	if len(a) > 42 {
+		panic("too many arguments to system call")
 	}
+
 	return strings.Join(a, ", ")
 }
 
@@ -1015,7 +979,7 @@ func {{.HelperName}}({{.HelperParamList}}) {{template "results" .}}{
 
 {{define "results"}}{{if .Rets.List}}{{.Rets.List}} {{end}}{{end}}
 
-{{define "syscall"}}{{.Rets.SetReturnValuesCode}}{{.Syscall}}(proc{{.DLLFuncName}}.Addr(),{{if le .ParamCount 15}} {{.ParamCount}},{{end}} {{.SyscallParamList}}){{end}}
+{{define "syscall"}}{{.Rets.SetReturnValuesCode}}{{.SyscallN}}(proc{{.DLLFuncName}}.Addr(), {{.SyscallParamList}}){{end}}
 
 {{define "tmpvarsreadback"}}{{range .Params}}{{if .TmpVarReadbackCode}}
 {{.TmpVarReadbackCode}}{{end}}{{end}}{{end}}

windows/mkwinsyscall/mkwinsyscall_test.go

@@ -50,25 +50,25 @@ func TestDLLFilenameEscaping(t *testing.T) {
 	}
 }
 
-func TestSyscallXGeneration(t *testing.T) {
+func TestSyscallNGeneration(t *testing.T) {
 	tests := []struct {
 		name        string
 		wantsysfunc string
 		sig         string
 	}{
 		{
 			name:        "syscall with 2 params",
-			wantsysfunc: "syscall.Syscall",
+			wantsysfunc: "syscall.SyscallN",
 			sig:         "Example(a1 *uint16, a2 *uint16) = ",
 		},
 		{
 			name:        "syscall with 6 params",
-			wantsysfunc: "syscall.Syscall6",
+			wantsysfunc: "syscall.SyscallN",
 			sig:         "Example(a1 *uint, a2 *uint, a3 *uint, a4 *uint, a5 *uint, a6 *uint) = ",
 		},
 		{
 			name:        "syscall with 15 params",
-			wantsysfunc: "syscall.Syscall15",
+			wantsysfunc: "syscall.SyscallN",
 			sig: strings.ReplaceAll(`Example(a1 *uint, a2 *uint, a3 *uint, a4 *uint, a5 *uint, a6 *uint,
 						a7 *uint, a8 *uint, a9 *uint, a10 *uint, a11 *uint, a12 *uint,
 						a13 *uint, a14 *uint, a15 *uint) = `, "\n", ""),