Revert "cmd/cgo: disable #cgo noescape/nocallback until Go 1.23"

src/cmd/cgo/doc.go

@@ -421,6 +421,30 @@ passing uninitialized C memory to Go code if the Go code is going to
 store pointer values in it. Zero out the memory in C before passing it
 to Go.
 
+# Optimizing calls of C code
+
+When passing a Go pointer to a C function the compiler normally ensures
+that the Go object lives on the heap. If the C function does not keep
+a copy of the Go pointer, and never passes the Go pointer back to Go code,
+then this is unnecessary. The #cgo noescape directive may be used to tell
+the compiler that no Go pointers escape via the named C function.
+If the noescape directive is used and the C function does not handle the
+pointer safely, the program may crash or see memory corruption.
+
+For example:
+
+	// #cgo noescape cFunctionName
+
+When a Go function calls a C function, it prepares for the C function to
+call back to a Go function. the #cgo nocallback directive may be used to
+tell the compiler that these preparations are not necessary.
+If the nocallback directive is used and the C function does call back into
+Go code, the program will panic.
+
+For example:
+
+	// #cgo nocallback cFunctionName
+
 # Special cases
 
 A few special C types which would normally be represented by a pointer

src/cmd/cgo/gcc.go

@@ -94,10 +94,8 @@ func (f *File) ProcessCgoDirectives() {
 				directive := fields[1]
 				funcName := fields[2]
 				if directive == "nocallback" {
-					fatalf("#cgo nocallback disabled until Go 1.23")
 					f.NoCallbacks[funcName] = true
 				} else if directive == "noescape" {
-					fatalf("#cgo noescape disabled until Go 1.23")
 					f.NoEscapes[funcName] = true
 				}
 			}

src/cmd/cgo/internal/test/test.go

@@ -117,8 +117,7 @@ int add(int x, int y) {
 
 // escape vs noescape
 
-// TODO(#56378): enable in Go 1.23:
-// #cgo noescape handleGoStringPointerNoescape
+#cgo noescape handleGoStringPointerNoescape
 void handleGoStringPointerNoescape(void *s) {}
 
 void handleGoStringPointerEscape(void *s) {}

src/cmd/cgo/internal/testerrors/testdata/notmatchedcfunction.go

@@ -5,8 +5,7 @@
 package main
 
 /*
-// TODO(#56378): change back to "#cgo noescape noMatchedCFunction: no matched C function" in Go 1.23
-// ERROR MESSAGE: #cgo noescape disabled until Go 1.23
+// ERROR MESSAGE: #cgo noescape noMatchedCFunction: no matched C function
 #cgo noescape noMatchedCFunction
 */
 import "C"

src/runtime/crash_cgo_test.go

@@ -754,7 +754,6 @@ func TestNeedmDeadlock(t *testing.T) {
 }
 
 func TestCgoNoCallback(t *testing.T) {
-	t.Skip("TODO(#56378): enable in Go 1.23")
 	got := runTestProg(t, "testprogcgo", "CgoNoCallback")
 	want := "function marked with #cgo nocallback called back into Go"
 	if !strings.Contains(got, want) {
@@ -763,7 +762,6 @@ func TestCgoNoCallback(t *testing.T) {
 }
 
 func TestCgoNoEscape(t *testing.T) {
-	t.Skip("TODO(#56378): enable in Go 1.23")
 	got := runTestProg(t, "testprogcgo", "CgoNoEscape")
 	want := "OK\n"
 	if got != want {

src/runtime/testdata/testprogcgo/cgonocallback.go

@@ -8,7 +8,8 @@ package main
 // But it do callback to go in this test, Go should crash here.
 
 /*
-// TODO(#56378): #cgo nocallback runCShouldNotCallback
+#cgo nocallback runCShouldNotCallback
+
 extern void runCShouldNotCallback();
 */
 import "C"

src/runtime/testdata/testprogcgo/cgonoescape.go

@@ -13,7 +13,7 @@ package main
 // 2. less than 100 new allocated heap objects after invoking withoutNoEscape 100 times.
 
 /*
-// TODO(#56378): #cgo noescape runCWithNoEscape
+#cgo noescape runCWithNoEscape
 
 void runCWithNoEscape(void *p) {
 }