internal/testpty: fix error handling

heschi · gopherbot · commit f85c282a18bb · 2023-01-25T18:38:54.000Z
When calling a c library function, you discover that an error has occurred, typically by looking at the return value of the function. Only after that can you use errno to figure out the cause of the error. Nothing about cgo changes that story -- you still have to look at the result before checking the error that represents errno. If not you can get false errors if the function happens to leak a non-zero errno. Fix testpty to check errors correctly. Change-Id: Idb95f8dd6a8ed63f653190c2e722e742cf50542b Reviewed-on: https://go-review.googlesource.com/c/go/+/463397 Run-TryBot: Heschi Kreinick <heschi@google.com> Reviewed-by: Michael Pratt <mpratt@google.com> Auto-Submit: Heschi Kreinick <heschi@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/internal/testpty/pty_cgo.go b/src/internal/testpty/pty_cgo.go
@@ -18,14 +18,14 @@ import "os"
 
 func open() (pty *os.File, processTTY string, err error) {
 	m, err := C.posix_openpt(C.O_RDWR)
-	if err != nil {
+	if m < 0 {
 		return nil, "", ptyError("posix_openpt", err)
 	}
-	if _, err := C.grantpt(m); err != nil {
+	if res, err := C.grantpt(m); res < 0 {
 		C.close(m)
 		return nil, "", ptyError("grantpt", err)
 	}
-	if _, err := C.unlockpt(m); err != nil {
+	if res, err := C.unlockpt(m); res < 0 {
 		C.close(m)
 		return nil, "", ptyError("unlockpt", err)
 	}

Original file line number	Diff line number	Diff line change
`@@ -18,14 +18,14 @@ import "os"`
`18`	`18`
`19`	`19`	`func open() (pty *os.File, processTTY string, err error) {`
`20`	`20`	`m, err := C.posix_openpt(C.O_RDWR)`
`21`		`- if err != nil {`
	`21`	`+ if m < 0 {`
`22`	`22`	`return nil, "", ptyError("posix_openpt", err)`
`23`	`23`	`}`
`24`		`- if _, err := C.grantpt(m); err != nil {`
	`24`	`+ if res, err := C.grantpt(m); res < 0 {`
`25`	`25`	`C.close(m)`
`26`	`26`	`return nil, "", ptyError("grantpt", err)`
`27`	`27`	`}`
`28`		`- if _, err := C.unlockpt(m); err != nil {`
	`28`	`+ if res, err := C.unlockpt(m); res < 0 {`
`29`	`29`	`C.close(m)`
`30`	`30`	`return nil, "", ptyError("unlockpt", err)`
`31`	`31`	`}`