gcc/libgo/runtime/panic.c

// Copyright 2012 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.

#include "runtime.h"
#include "malloc.h"
#include "go-defer.h"
#include "go-panic.h"

// Code related to defer, panic and recover.

uint32 runtime_panicking;
static Lock paniclk;

// Allocate a Defer, usually using per-P pool.
// Each defer must be released with freedefer.
Defer*
runtime_newdefer()
{
	Defer *d;
	P *p;

	d = nil;
	p = runtime_m()->p;
	d = p->deferpool;
	if(d)
		p->deferpool = d->__next;
	if(d == nil) {
		// deferpool is empty
		d = runtime_malloc(sizeof(Defer));
	}
	return d;
}

// Free the given defer.
// The defer cannot be used after this call.
void
runtime_freedefer(Defer *d)
{
	P *p;

	if(d->__special)
		return;
	p = runtime_m()->p;
	d->__next = p->deferpool;
	p->deferpool = d;
	// No need to wipe out pointers in argp/pc/fn/args,
	// because we empty the pool before GC.
}

// Run all deferred functions for the current goroutine.
// This is noinline for go_can_recover.
static void __go_rundefer (void) __attribute__ ((noinline));
static void
__go_rundefer(void)
{
	G *g;
	Defer *d;

	g = runtime_g();
	while((d = g->defer) != nil) {
		void (*pfn)(void*);

		g->defer = d->__next;
		pfn = d->__pfn;
		d->__pfn = nil;
		if (pfn != nil)
			(*pfn)(d->__arg);
		runtime_freedefer(d);
	}
}

void
runtime_startpanic(void)
{
	M *m;

	m = runtime_m();
	if(runtime_mheap.cachealloc.size == 0) { // very early
		runtime_printf("runtime: panic before malloc heap initialized\n");
		m->mallocing = 1; // tell rest of panic not to try to malloc
	} else if(m->mcache == nil) // can happen if called from signal handler or throw
		m->mcache = runtime_allocmcache();
	switch(m->dying) {
	case 0:
		m->dying = 1;
		if(runtime_g() != nil)
			runtime_g()->writebuf = nil;
		runtime_xadd(&runtime_panicking, 1);
		runtime_lock(&paniclk);
		if(runtime_debug.schedtrace > 0 || runtime_debug.scheddetail > 0)
			runtime_schedtrace(true);
		runtime_freezetheworld();
		return;
	case 1:
		// Something failed while panicing, probably the print of the
		// argument to panic().  Just print a stack trace and exit.
		m->dying = 2;
		runtime_printf("panic during panic\n");
		runtime_dopanic(0);
		runtime_exit(3);
	case 2:
		// This is a genuine bug in the runtime, we couldn't even
		// print the stack trace successfully.
		m->dying = 3;
		runtime_printf("stack trace unavailable\n");
		runtime_exit(4);
	default:
		// Can't even print!  Just exit.
		runtime_exit(5);
	}
}

void
runtime_dopanic(int32 unused __attribute__ ((unused)))
{
	G *g;
	static bool didothers;
	bool crash;
	int32 t;

	g = runtime_g();
	if(g->sig != 0)
		runtime_printf("[signal %x code=%p addr=%p]\n",
			       g->sig, (void*)g->sigcode0, (void*)g->sigcode1);

	if((t = runtime_gotraceback(&crash)) > 0){
		if(g != runtime_m()->g0) {
			runtime_printf("\n");
			runtime_goroutineheader(g);
			runtime_traceback();
			runtime_printcreatedby(g);
		} else if(t >= 2 || runtime_m()->throwing > 0) {
			runtime_printf("\nruntime stack:\n");
			runtime_traceback();
		}
		if(!didothers) {
			didothers = true;
			runtime_tracebackothers(g);
		}
	}
	runtime_unlock(&paniclk);
	if(runtime_xadd(&runtime_panicking, -1) != 0) {
		// Some other m is panicking too.
		// Let it print what it needs to print.
		// Wait forever without chewing up cpu.
		// It will exit when it's done.
		static Lock deadlock;
		runtime_lock(&deadlock);
		runtime_lock(&deadlock);
	}
	
	if(crash)
		runtime_crash();

	runtime_exit(2);
}

bool
runtime_canpanic(G *gp)
{
	M *m = runtime_m();
	byte g;

	USED(&g);  // don't use global g, it points to gsignal

	// Is it okay for gp to panic instead of crashing the program?
	// Yes, as long as it is running Go code, not runtime code,
	// and not stuck in a system call.
	if(gp == nil || gp != m->curg)
		return false;
	if(m->locks-m->softfloat != 0 || m->mallocing != 0 || m->throwing != 0 || m->gcing != 0 || m->dying != 0)
		return false;
	if(gp->status != Grunning)
		return false;
#ifdef GOOS_windows
	if(m->libcallsp != 0)
		return false;
#endif
	return true;
}

void
runtime_throw(const char *s)
{
	M *mp;

	mp = runtime_m();
	if(mp->throwing == 0)
		mp->throwing = 1;
	runtime_startpanic();
	runtime_printf("fatal error: %s\n", s);
	runtime_dopanic(0);
	*(int32*)0 = 0;	// not reached
	runtime_exit(1);	// even more not reached
}

void
runtime_panicstring(const char *s)
{
	Eface err;

	if(runtime_m()->mallocing) {
		runtime_printf("panic: %s\n", s);
		runtime_throw("panic during malloc");
	}
	if(runtime_m()->gcing) {
		runtime_printf("panic: %s\n", s);
		runtime_throw("panic during gc");
	}
	if(runtime_m()->locks) {
		runtime_printf("panic: %s\n", s);
		runtime_throw("panic holding locks");
	}
	runtime_newErrorCString(s, &err);
	runtime_panic(err);
}

void runtime_Goexit (void) __asm__ (GOSYM_PREFIX "runtime.Goexit");

void
runtime_Goexit(void)
{
	__go_rundefer();
	runtime_goexit();
}

void
runtime_panicdivide(void)
{
	runtime_panicstring("integer divide by zero");
}