[英]Boost IPC Message_Queue try_receive throws interprocess_exception::library_error
I am making interprocess communication between two of my processes with boost::interprocess::message_queue. 我正在使用boost :: interprocess :: message_queue在两个进程之间进行进程间通信。
This is the first time I'm using it so this exception isn't clear to me because I cannot find any documentation on it. 这是我第一次使用它,因此我看不到该异常,因为我找不到关于它的任何文档。
I have my classes setup as following: 我的班级设置如下:
struct Pos{float X,Y,Z;};
struct Quat{float W,X,Y,Z;};
typedef unsigned char Byte;
struct NPCDataFoot
{
//some Pos and Quat variables here too
unsigned short AnimationIndex;
void Apply(NPCDataFoot &data){AnimationIndex=data.AnimationIndex;}
NPCDataFoot(){AnimationIndex=0;}
};
struct NPCDataVehicle
{
//many many more
unsigned short lrAnalog;
void Apply(NPCDataVehicle &data){lrAnalog=data.lrAnalog;}
NPCDataVehicle(){lrAnalog = 0;}
};
enum TransmissionDataType{
TDT_NewNPC,//many more...
};
const unsigned short QueueMaxSize = 256;
struct ExchangeData
{
unsigned short CommandType;
unsigned short NPCPlayerID;
Byte State;
NPCDataFoot OnFootData;
NPCDataVehicle InCarData;
float MoveSpeed;
Pos MoveToPos;
//206
ExchangeData(unsigned short CommandType = 0, unsigned short NPCPlayerid = 0xFFFF)
: CommandType(CommandType), NPCPlayerID(NPCPlayerid)
{}
ExchangeData(unsigned short CommandType, unsigned short NPCPlayerid, NPCDataFoot& foot_data, NPCDataVehicle& car_data)
: CommandType(CommandType), NPCPlayerID(NPCPlayerid), OnFootData(foot_data), InCarData(car_data)
{}
};
both my programs are set to compile with the /zp1 flag (Align structures/classes to 1-byte alignment). 我的两个程序都设置为使用/ zp1标志进行编译(将结构/类对齐为1字节对齐)。
now whenever I reach this code: 现在,只要我到达此代码:
ServerMsgQueue * message_queue = NULL;
PLUGIN_EXPORT void PLUGIN_CALL
ProcessTick()
{
static bool init = false;
static ExchangeData DataTransmision;
if(!init)
{
try
{
ServerMsgQueue = new message_queue(open_or_create
,string_format("REMOTESHAREDMEMORYBTWNPRCS%04x",GetServerVarAsInt("port")).c_str()
,1024 * QueueMaxSize,sizeof(ExchangeData));
}
catch(interprocess_exception &ex)
{
std::cout << ex.what() << ":" << __FILE__ << ":" << __FUNCTION__ << ":" << __LINE__ << std::endl;
}
init = true;
}
static unsigned int unused;
if(ServerMsgQueue)
{
try
{
if(ServerMsgQueue->try_receive(&DataTransmision,sizeof(ExchangeData),unused,unused))
{
switch(DataTransmision.CommandType)
{//some cases
default:{std::cout << "UNKNOWN RECEIVED DATA!!!" << std::endl;break;}
}
}
}
catch(interprocess_exception &ex)
{
//this happens always
std::cout << ex.what() << ":" << __FILE__ << ":" << __FUNCTION__ << ":" << __LINE__ << std::endl;
}
}
}
The application keeps issuing "boost::interprocess_exception::library_error" in the block where try_receive
is being used. 应用程序在使用
try_receive
的块中不断发出“ boost :: interprocess_exception :: library_error”。
What am I doing wrong in this case? 我在这种情况下做错了什么? I'm sure the data send is the same size because 1) i use the same header and 2) I compile with the same options.
我确定数据发送的大小是相同的,因为1)我使用相同的标头,并且2)我使用相同的选项进行编译。
I have confirmed that the variable sizes are the same with the following code in both programs: 我已经确认两个程序中的变量大小与以下代码相同:
MessageBox(NULL,string_format(
"Pos(%d):Quat(%d):NPCDataFoot(%d):NPCDataVehicle(%d):ExchangeData(%d)",
sizeof(Pos),sizeof(Quat),sizeof(NPCDataFoot),sizeof(NPCDataVehicle),sizeof(ExchangeData)).c_str()
,"Reported sizes Client",0);
Edit: I seem have "solved" it.. magicly; 编辑:我似乎已经“解决”了它。
It seems that this code was the error: 似乎此代码是错误:
static unsigned int unused;
if(ServerMsgQueue->try_receive(&DataTransmision,sizeof(ExchangeData),unused,unused))
changed it to 改成
unsigned int Priority;
size_t sizexxx;
if(ServerMsgQueue->try_receive(&DataTransmision,sizeof(ExchangeData),sizexxx,Priority))
Can someone explain why this works and the other code not? 有人可以解释为什么这行得通,而其他代码行不通吗?
This is most likely caused by your use of /zp1
. 这很可能是由于您使用
/zp1
引起的。 Your program and the libraries to which it links will think that structures have different sizes and/or member locations. 您的程序及其链接到的库将认为结构具有不同的大小和/或成员位置。 Don't do that.
不要那样做
See the source code for message_queue::do_receive
(called from message_queue::try_receive
); 参见
message_queue::do_receive
的源代码(从message_queue::try_receive
); do_receive
first writes the message size to the "out" parameter recvd_size
(a reference to unused
in your code), then writes the priority to the "out" parameter priority
( also a reference to unused
in your code -- thus effectively overwriting recvd_size
with the priority
value). do_receive
首先将消息大小写入“ out”参数recvd_size
(对代码中unused
的引用),然后将优先级写入“ out”参数priority
( 也对代码中unused
的引用),从而有效地覆盖了recvd_size
priority
值)。 Immediately below, the call to memcpy
uses the now incorrect recvd_size
, leading to the behaviour you observed (incomplete copy or buffer overrun, depending on priority
). 在紧下方,对
memcpy
的调用使用了现在不正确的recvd_size
,从而导致您观察到的行为(不完整的副本或缓冲区溢出,具体取决于priority
)。
Arguably, the author of the library should have used the original top_msg->len
(instead of the "out" parameter recvd_size
) for the memcpy
bytecount. 可以说,该库的作者应该对
memcpy
字节计数使用原始的top_msg->len
(而不是“ out”参数recvd_size
)。 However, in order to avoid these kinds of surprises, always use distinct variables for "out" parameters (call them unused1
and unused2
if you so desire). 但是,为了避免此类意外,请始终对“输出”参数使用不同的变量(如果需要,可以将它们
unused1
“ unused1
和“ unused2
)。
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