golangpanic原理

数据结构与底层实现 Goroutine结构体

stack（栈内存范围） 结构体类型，包含 lo（低地址）和 hi（高地址）两个 uintptr 字段，描述 Goroutine 的栈内存区间 [lo, hi)。初始栈大小为 2KB，可动态扩容至 1GB。

m（Machine 绑定） 指向当前运行此 Goroutine 的内核线程（M）。调度器通过 M 将 Goroutine 映射到操作系统线程。

_panic 和 _defer（异常与延迟调用链）

_panic：指向当前最内层的 panic 结构体链表，处理异常传播。_defer：指向延迟调用（defer）链表，按后进先出（LIFO）顺序执行清理操作。 type g struct { // Stack parameters. // stack describes the actual stack memory: [stack.lo, stack.hi). // stackguard0 is the stack pointer compared in the Go stack growth prologue. // It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption. // stackguard1 is the stack pointer compared in the //go:systemstack stack growth prologue. // It is stack.lo+StackGuard on g0 and gsignal stacks. // It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash). stack stack // offset known to runtime/cgo stackguard0 uintptr // offset known to liblink stackguard1 uintptr // offset known to liblink _panic *_panic // innermost panic - offset known to liblink _defer *_defer // innermost defer m *m // current m; offset known to arm liblink sched gobuf ...... } panic结构体

从上述Goroutine结构体的定义，我们可以发现每一个Goroutine维护一个panic的链表，panic存储在栈上。

// _panic 保存了一个活跃的 panic 信息。 // _panic 的值必须仅存在于栈上。 // argp 和 link 字段是栈指针，但在栈增长时无需特殊处理： // 由于它们是指针类型且 _panic 值仅存在于栈上， // 常规的栈指针调整机制会自动处理这些字段。 type _panic struct { argp unsafe.Pointer // pointer to arguments of deferred call run during panic; cannot move - known to liblink arg any // argument to panic link *_panic // link to earlier panic // startPC and startSP track where _panic.start was called. startPC uintptr startSP unsafe.Pointer // The current stack frame that we're running deferred calls for. sp unsafe.Pointer lr uintptr fp unsafe.Pointer // retpc stores the PC where the panic should jump back to, if the // function last returned by _panic.next() recovers the panic. retpc uintptr // Extra state for handling open-coded defers. deferBitsPtr *uint8 slotsPtr unsafe.Pointer recovered bool // whether this panic has been recovered goexit bool deferreturn bool } 注意事项

golang中每个goroutine维护自己的panic信息，并不是全局的，所以，如果需要捕获panic信息需要在每个goroutine中处理。

所以，在下面的这个案例中recover不能捕获到panic信息。如果需要捕获到，需要在每个协程中都执行recover的逻辑。

func main() { defer func() { if r := recover(); r != nil { log.Printf("Recovered from panic: %v", r) os.Exit(1) } }() // 业务代码... go func() { testPanic() }() time.Sleep(1 * time.Second) }