src/runtime/testdata/testprogcgo/tracebackctxt.go

// Copyright 2016 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 main

// Test the context argument to SetCgoTraceback.
// Use fake context, traceback, and symbolizer functions.

/*
// Defined in tracebackctxt_c.c.
extern void C1(void);
extern void C2(void);
extern void tcContext(void*);
extern void tcContextSimple(void*);
extern void tcTraceback(void*);
extern void tcSymbolizer(void*);
extern int getContextCount(void);
extern void TracebackContextPreemptionCallGo(int);
extern void TracebackContextProfileCallGo(void);
*/
import "C"

import (
	"fmt"
	"io"
	"runtime"
	"runtime/pprof"
	"sync"
	"sync/atomic"
	"unsafe"
)

func init() {
	register("TracebackContext", TracebackContext)
	register("TracebackContextPreemption", TracebackContextPreemption)
	register("TracebackContextProfile", TracebackContextProfile)
}

var tracebackOK bool

func TracebackContext() {
	runtime.SetCgoTraceback(0, unsafe.Pointer(C.tcTraceback), unsafe.Pointer(C.tcContext), unsafe.Pointer(C.tcSymbolizer))
	C.C1()
	if got := C.getContextCount(); got != 0 {
		fmt.Printf("at end contextCount == %d, expected 0\n", got)
		tracebackOK = false
	}
	if tracebackOK {
		fmt.Println("OK")
	}
}

//export G1
func G1() {
	C.C2()
}

//export G2
func G2() {
	pc := make([]uintptr, 32)
	n := runtime.Callers(0, pc)
	cf := runtime.CallersFrames(pc[:n])
	var frames []runtime.Frame
	for {
		frame, more := cf.Next()
		frames = append(frames, frame)
		if !more {
			break
		}
	}

	want := []struct {
		function string
		line     int
	}{
		{"main.G2", 0},
		{"cFunction", 0x10200},
		{"cFunction", 0x200},
		{"cFunction", 0x10201},
		{"cFunction", 0x201},
		{"main.G1", 0},
		{"cFunction", 0x10100},
		{"cFunction", 0x100},
		{"main.TracebackContext", 0},
	}

	ok := true
	i := 0
wantLoop:
	for _, w := range want {
		for ; i < len(frames); i++ {
			if w.function == frames[i].Function {
				if w.line != 0 && w.line != frames[i].Line {
					fmt.Printf("found function %s at wrong line %#x (expected %#x)\n", w.function, frames[i].Line, w.line)
					ok = false
				}
				i++
				continue wantLoop
			}
		}
		fmt.Printf("did not find function %s in\n", w.function)
		for _, f := range frames {
			fmt.Println(f)
		}
		ok = false
		break
	}
	tracebackOK = ok
	if got := C.getContextCount(); got != 2 {
		fmt.Printf("at bottom contextCount == %d, expected 2\n", got)
		tracebackOK = false
	}
}

// Issue 47441.
func TracebackContextPreemption() {
	runtime.SetCgoTraceback(0, unsafe.Pointer(C.tcTraceback), unsafe.Pointer(C.tcContextSimple), unsafe.Pointer(C.tcSymbolizer))

	const funcs = 10
	const calls = 1e5
	var wg sync.WaitGroup
	for i := 0; i < funcs; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			for j := 0; j < calls; j++ {
				C.TracebackContextPreemptionCallGo(C.int(i*calls + j))
			}
		}(i)
	}
	wg.Wait()

	fmt.Println("OK")
}

//export TracebackContextPreemptionGoFunction
func TracebackContextPreemptionGoFunction(i C.int) {
	// Do some busy work.
	fmt.Sprintf("%d\n", i)
}

// Regression test for issue 71395.
//
// The SIGPROF handler can call the SetCgoTraceback traceback function if the
// context function is also provided. Ensure that call is safe.
func TracebackContextProfile() {
	runtime.SetCgoTraceback(0, unsafe.Pointer(C.tcTraceback), unsafe.Pointer(C.tcContextSimple), unsafe.Pointer(C.tcSymbolizer))

	if err := pprof.StartCPUProfile(io.Discard); err != nil {
		panic(fmt.Sprintf("error starting CPU profile: %v", err))
	}
	defer pprof.StopCPUProfile()

	const calls = 1e5
	var wg sync.WaitGroup
	for i := 0; i < runtime.GOMAXPROCS(0); i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := 0; j < calls; j++ {
				C.TracebackContextProfileCallGo()
			}
		}()
	}
	wg.Wait()

	fmt.Println("OK")
}

var sink atomic.Pointer[byte]

//export TracebackContextProfileGoFunction
func TracebackContextProfileGoFunction() {
	// Issue 71395 occurs when SIGPROF lands on code running on the system
	// stack in a cgo callback. The allocator uses the system stack.
	b := make([]byte, 128)
	sink.Store(&b[0])
}