1 files changed, 69 insertions, 0 deletions
diff --git a/src/runtime/exithook.go b/src/runtime/exithook.go
new file mode 100644
index 0000000..65b426b
--- /dev/null
+++ b/src/runtime/exithook.go
@@ -0,0 +1,69 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+// addExitHook registers the specified function 'f' to be run at
+// program termination (e.g. when someone invokes os.Exit(), or when
+// main.main returns). Hooks are run in reverse order of registration:
+// first hook added is the last one run.
+//
+// CAREFUL: the expectation is that addExitHook should only be called
+// from a safe context (e.g. not an error/panic path or signal
+// handler, preemption enabled, allocation allowed, write barriers
+// allowed, etc), and that the exit function 'f' will be invoked under
+// similar circumstances. That is the say, we are expecting that 'f'
+// uses normal / high-level Go code as opposed to one of the more
+// restricted dialects used for the trickier parts of the runtime.
+func addExitHook(f func(), runOnNonZeroExit bool) {
+	exitHooks.hooks = append(exitHooks.hooks, exitHook{f: f, runOnNonZeroExit: runOnNonZeroExit})
+}
+
+// exitHook stores a function to be run on program exit, registered
+// by the utility runtime.addExitHook.
+type exitHook struct {
+	f                func() // func to run
+	runOnNonZeroExit bool   // whether to run on non-zero exit code
+}
+
+// exitHooks stores state related to hook functions registered to
+// run when program execution terminates.
+var exitHooks struct {
+	hooks            []exitHook
+	runningExitHooks bool
+}
+
+// runExitHooks runs any registered exit hook functions (funcs
+// previously registered using runtime.addExitHook). Here 'exitCode'
+// is the status code being passed to os.Exit, or zero if the program
+// is terminating normally without calling os.Exit.
+func runExitHooks(exitCode int) {
+	if exitHooks.runningExitHooks {
+		throw("internal error: exit hook invoked exit")
+	}
+	exitHooks.runningExitHooks = true
+
+	runExitHook := func(f func()) (caughtPanic bool) {
+		defer func() {
+			if x := recover(); x != nil {
+				caughtPanic = true
+			}
+		}()
+		f()
+		return
+	}
+
+	finishPageTrace()
+	for i := range exitHooks.hooks {
+		h := exitHooks.hooks[len(exitHooks.hooks)-i-1]
+		if exitCode != 0 && !h.runOnNonZeroExit {
+			continue
+		}
+		if caughtPanic := runExitHook(h.f); caughtPanic {
+			throw("internal error: exit hook invoked panic")
+		}
+	}
+	exitHooks.hooks = nil
+	exitHooks.runningExitHooks = false
+}