【发布时间】：2016-03-16 14:19:20
【问题描述】：
我已经实现了一个优先级来自asio examples 的任务队列和一个使用这个队列的计时器类。代码如下：
priority_task_queue.h
class handler_priority_queue
{
private:
class queued_handler{
private:
size_t _priority;
std::function<void()> _function;
public:
queued_handler(size_t p, std::function<void()> f): _priority(p), _function(f){}
friend bool operator<(const queued_handler& a, const queued_handler& b){
return a._priority < b._priority;
}
void operator()() {
_function();
}
};
std::priority_queue<queued_handler> _handlers;
public:
// A generic wrapper class for handlers to allow the invocation to be hooked.
template <typename Handler> class wrapped_handler
{
private:
handler_priority_queue& _queue;
size_t _priority;
Handler _handler;
public:
handler_priority_queue& queue() {return _queue;}
size_t priority() {return _priority;}
wrapped_handler(handler_priority_queue& q, size_t p, Handler h)
: _queue(q), _priority(p), _handler(h){}
template <typename ...Args>
void operator()(Args&&... args){
_handler(std::forward<Args>(args)...);
}
};
template <typename Handler> wrapped_handler<Handler> wrap(size_t priority, Handler handler){
return wrapped_handler<Handler>(*this, priority, handler);
}
void add(size_t priority, std::function<void()> function);
void execute_all();
void execute_one();
bool empty();
};
// Custom invocation hook for wrapped handlers.
template <typename Function, typename Handler>
void asio_handler_invoke(Function f, handler_priority_queue::wrapped_handler<Handler>* h){
h->queue().add(h->priority(), f);
std::cout<<"LLAMANDO AL INVOKE"<<std::endl; //BORRAR!!
}
class C_priority_task_queue{
private:
asio::io_service& _io;
handler_priority_queue _pri_queue;
public:
template <typename Handler> handler_priority_queue::wrapped_handler<Handler> wrap(int priority, Handler handler){
return _pri_queue.wrap(priority, handler);
}
explicit C_priority_task_queue(asio::io_service& io): _io(io){}
C_priority_task_queue(C_priority_task_queue const&) = delete;
C_priority_task_queue& operator =(C_priority_task_queue const&) = delete;
asio::io_service& io() {return _io;}
void run();
};
priority_task_queue.cpp
void handler_priority_queue::add(size_t priority, std::function<void()> function){
_handlers.push(queued_handler(priority, function));
}
void handler_priority_queue::execute_one(){
if(!_handlers.empty()){
queued_handler handler = _handlers.top();
handler();
_handlers.pop();
}
}
bool handler_priority_queue::empty(){
return _handlers.empty();
}
void C_priority_task_queue::run(){
while (_io.run_one())
{
_io.poll();
while(!_pri_queue.empty())
{
_io.poll();
_pri_queue.execute_one();
}
}
}
base_timer.h
class C_timer {
private:
asio::high_resolution_timer _timer;
uint8_t _timer_id;
C_priority_task_queue& _prio_queue;
void timer_handler_internal(const asio::error_code& e, uint8_t timer_id, const uint64_t sched_time);
virtual void timer_handler(const uint64_t sched_time)=0;
public:
size_t _priority;
explicit C_timer(C_priority_task_queue& prio_queue, size_t priority);
virtual ~C_timer();
void set_timer(uint64_t sched_time);
int cancel();
};
base_timer.cpp
C_timer::C_timer(C_priority_task_queue& prio_queue, size_t priority):
_timer(prio_queue.io()), _timer_id(0), _prio_queue(prio_queue), _priority(priority){}
C_timer::~C_timer(){}
void C_timer::set_timer(uint64_t sched_time){
++_timer_id;
_timer.expires_at(std::chrono::time_point<std::chrono::high_resolution_clock>(std::chrono::milliseconds(sched_time)));
_timer.async_wait(_prio_queue.wrap(_priority, std::bind(&C_timer::timer_handler_internal, this,
std::placeholders::_1/*error*/, _timer_id, sched_time)));
}
int C_timer::cancel(){
++_timer_id;
return _timer.cancel();
}
void C_timer::timer_handler_internal(const asio::error_code& e, uint8_t timer_id,
const uint64_t sched_time){
if(e==asio::error::operation_aborted || timer_id != _timer_id){
return;
}
timer_handler(sched_time);
}
测试类
class C_timer_test: public C_timer{
private:
int _period;
virtual void timer_handler(const uint64_t sched_time) override{
std::cout<<"timer fired"<<std::endl;
uint64_t current_time = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now().time_since_epoch()).count();
set_timer(current_time + _period);
}
public:
C_timer_test(C_priority_task_queue& prio_queue, int priority, int period):C_timer(prio_queue, priority), _periodo(period){}
virtual ~C_timer_test(){}
void run(uint64_t delay=0){
uint64_t time = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now().time_since_epoch()).count();
set_timer(time + delay);
}
};
问题是如果我执行这个：
int main()
{
asio::io_service io;
C_priority_task_queue prio_queue(io);
asio::io_service::work w(io);
C_timer_test ti1(prio_queue, 0, 2000);
ti1.run();
prio_queue.run();
return 0;
}
我遇到了分段错误。
但是，如果我执行以下代码，它可以正常工作：
int main()
{
asio::io_service io;
C_priority_task_queue prio_queue(io);
asio::high_resolution_timer _timer1(io);
asio::io_service::work w(io);
C_timer_test ti1(prio_queue, 0, 2000);
ti1.run();
prio_queue.run();
return 0;
}
这两段代码之间的唯一区别在于第二个主要部分，我添加了以下行asio::high_resolution_timer _timer1(io);，我在任何地方都没有使用过。
调试程序我发现信号在这一行上升：
func_(&owner, this, ec, bytes_transferred); 在文件中task_io_service_operation.hpp
我使用的是 asio 版本 1.10.6。
对可能发生的事情有什么建议吗？
来自 gdb 的回溯：
gdb ./main
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
This GDB was configured as "i686-linux-gnu".
(gdb) r
[libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
Program received signal SIGSEGV, Segmentation fault.
0x0805f0d4 in ?? ()
(gdb) backtrace
#0 0x0805f0d4 in ?? ()
#1 0x080529fb in asio::detail::task_io_service::do_run_one (this=0x805f030, lock=..., this_thread=..., ec=...) at /src/cpp/external_lib/asio/include/asio/detail/impl/task_io_service.ipp:371
#2 0x080526ce in asio::detail::task_io_service::run_one (this=0x805f030, ec=...) at /src/cpp/external_lib/asio/include/asio/detail/impl/task_io_service.ipp:169
#3 0x08052c68 in asio::io_service::run_one (this=0xbffff08c) at /src/cpp/external_lib/asio/include/asio/impl/io_service.ipp:71
#4 0x08051f32 in C_priority_task_queue::run (this=0xbffff094) at priority_task_queue.cpp:19
#5 0x08049ac3 in main () at main.cpp:46
这里有 MakeFile：
TARGET=main
SOURCES= main.cpp base_timer.cpp priority_task_queue.cpp
SOURCE_DIR=.
INCLUDE_LIB= -L/src/cpp/libcore
INCLUDE_DIR=-I/src/cpp/external_lib/asio/include \
-I/src/cpp/libcore/include
INSTALL_DIR=.
LIB=-pthread
CXX=g++
CFLAGS=-Wall -fexceptions -fpermissive -std=c++11 -DASIO_STANDALONE
CFLAGS_DEBUG = -g3 -DDEBUG
OBJDIR_DEBUG=obj
BINDIR_DEBUG=.
OBJECTS_DEBUG:= $(addprefix $(OBJDIR_DEBUG)/,$(SOURCES:.cpp=.o))
all: debug
$(OBJDIR_DEBUG)/%.o: $(SOURCE_DIR)/%.cpp
@test -d $(OBJDIR_DEBUG) || mkdir -p $(OBJDIR_DEBUG)
$(CXX) $(CFLAGS) $(CFLAGS_DEBUG) $(INCLUDE_DIR) -c $< -o $@
debug: $(OBJECTS_DEBUG)
@test -d $(BINDIR_DEBUG) || mkdir -p $(BINDIR_DEBUG)
$(CXX) -o $(BINDIR_DEBUG)/$(TARGET) $^ $(INCLUDE_LIB) $(LIB)
更新
我的调查，我发现如果我在 .h 中定义 base_timer 成员（基本上是 asio::high_resolution_timer）初始化，代码运行正常，但如果我在 .cpp 中这样做，代码会崩溃。
我的意思是，
explicit C_timer(C_priority_task_queue& prio_queue, size_t priority):
_timer(prio_queue.io()), _timer_id(0), _prio_queue(prio_queue), _priority(priority){}
在 .h 中有效，但是
C_timer::C_timer(C_priority_task_queue& prio_queue, size_t priority):
_timer(prio_queue.io()), _timer_id(0), _prio_queue(prio_queue), _priority(priority){}
在 .cpp 中失败
【问题讨论】：
-
我认为您错过了对
io.run()的呼叫。io_service类需要在其上运行的线程。编辑：run_one()调用可能不够，如果您打算使用计时器，您可能应该有一个线程供io_service运行。 -
@nimble_ninja 这不是问题。只是这部分取自 asio 示例（执行 while(io.run_one()) 与调用 io.run() 相同）。无论如何，正如我在问题中提到的，如果我添加了这一行，asio::high_resolution_timer _timer1(io)，与其余代码无关，程序运行完美。如果我省略它，它会引发分段错误。
-
在调试器中运行它会发生什么？崩溃的回溯是什么？
-
除了“不自然”与 chrono 杂耍（时间点或持续时间，选择一个！）代码看起来没问题。我无法重现任何故障（GCC、linux）：coliru.stacked-crooked.com/a/33f400874358b133
-
如果添加随机变量会使问题出现/消失，你应该想到Undefined Behaviour，使用静态分析、valgrind/purify/...和代码审查来找到你的罪魁祸首。 Valgrind、ASAN 和 UBSAN 在我的 PC 上运行干净
标签： c++ c++11 segmentation-fault boost-asio