windows: use unsafe.Add instead of pointer arithmetic on a uintptr

Bryan C. Mills · gopherbot · commit ca59edaa5a76 · 2023-05-03T21:21:24.000Z
The existing uintptr arithmetic is arguably valid because the environment block is not located within the Go heap (see golang/go#58625). However, unsafe.Add (added in Go 1.17) expresses the same logic with fewer conversions, and in addition avoids triggering the unsafeptr vet check. For golang/go#41205. Change-Id: Ifc509279a13fd707be570908ec779d8518b4f75b Reviewed-on: https://go-review.googlesource.com/c/sys/+/492415 Reviewed-by: Ian Lance Taylor <iant@google.com> Run-TryBot: Bryan Mills <bcmills@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Auto-Submit: Bryan Mills <bcmills@google.com>
diff --git a/windows/env_windows.go b/windows/env_windows.go
@@ -37,14 +37,14 @@ func (token Token) Environ(inheritExisting bool) (env []string, err error) {
 		return nil, err
 	}
 	defer DestroyEnvironmentBlock(block)
-	blockp := uintptr(unsafe.Pointer(block))
+	blockp := unsafe.Pointer(block)
 	for {
-		entry := UTF16PtrToString((*uint16)(unsafe.Pointer(blockp)))
+		entry := UTF16PtrToString((*uint16)(blockp))
 		if len(entry) == 0 {
 			break
 		}
 		env = append(env, entry)
-		blockp += 2 * (uintptr(len(entry)) + 1)
+		blockp = unsafe.Add(blockp, 2*(len(entry)+1))
 	}
 	return env, nil
 }

Original file line number	Diff line number	Diff line change
`@@ -37,14 +37,14 @@ func (token Token) Environ(inheritExisting bool) (env []string, err error) {`
`37`	`37`	`return nil, err`
`38`	`38`	`}`
`39`	`39`	`defer DestroyEnvironmentBlock(block)`
`40`		`- blockp := uintptr(unsafe.Pointer(block))`
	`40`	`+ blockp := unsafe.Pointer(block)`
`41`	`41`	`for {`
`42`		`- entry := UTF16PtrToString((*uint16)(unsafe.Pointer(blockp)))`
	`42`	`+ entry := UTF16PtrToString((*uint16)(blockp))`
`43`	`43`	`if len(entry) == 0 {`
`44`	`44`	`break`
`45`	`45`	`}`
`46`	`46`	`env = append(env, entry)`
`47`		`- blockp += 2 * (uintptr(len(entry)) + 1)`
	`47`	`+ blockp = unsafe.Add(blockp, 2*(len(entry)+1))`
`48`	`48`	`}`
`49`	`49`	`return env, nil`
`50`	`50`	`}`