compiler error when calling a std::thread function with parameters C++

Question

I am trying to invoke a function from a new thread. The function takes a bunch of parameters.

std::thread signingThread(curlWrapper->SendDataToServer,username, password, serverURL, data);

Here is the function protoype

int LibCurlWrapper::SendDataToServer(const std::string& username, const std::string& password, const std::string& serverURL, const std::vector<unsigned char> &vData)

Compiler Error

error: no matching function for call to 'std::thread::thread(, std::string&, std::string&, std::string&, std::vector&)' std::thread signingThread(curlWrapper->SendDataToServer,username, password, serverURL, data);

curlWrapper->SendDataToServer is nonsense, that's not valid C++. There are hundreds of questions on StackOverflow about launching a std::thread to run a member function. — Jonathan Wakely
– Jonathan Wakely, Commented Aug 14, 2015 at 18:12
LibCurlWrapper *curlWrapper = new LibCurlWrapper; Why is that nonsense? — nateN
– nateN, Commented Aug 14, 2015 at 18:14
@Jonathan Wakely Also, I have searched a lot before posting this...but nothing that I saw or read has worked. If you have a link please do share. Thnx — nateN
– nateN, Commented Aug 14, 2015 at 18:22
Because you can't refer to a member function like that. You can use curlWrapper->SendDataToServer in a function call if you follow it with an argument list, but you didn't do that. You need to construct the thread with a pointer-to-member-function that refers to the member function and with a pointer/reference to the object to call the function on. Here's one example of an existing question: stackoverflow.com/questions/10673585/… — Jonathan Wakely
– Jonathan Wakely, Commented Aug 14, 2015 at 18:31

songyuanyao · Accepted Answer · 2015-08-14 18:18:30Z

2

You need to specify a function to std::thread, while curlWrapper->SendDataToServer doesn't and couldn't. (Although curlWrapper->SendDataToServer() means call SendDataToServer() on curlWrapper.)

Change it to:

std::thread signingThread(&LibCurlWrapper::SendDataToServer, curlWrapper, username, password, serverURL, data);

edited Aug 14, 2015 at 18:18

answered Aug 14, 2015 at 18:09

songyuanyao

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4 Comments

nateN Over a year ago

When I try what you have suggested I get the following compiler error. error: no type named 'type' in 'class std::result_of<std::_Mem_fn<int (LibCurlWrapper::*)(const std::basic_string<char>&, const std::basic_string<char>&, const std::basic_string<char>&, const std::vector<unsigned char>&)>(std::basic_string<char>, std::basic_string<char>, std::basic_string<char>, std::vector<unsigned char>)>' typedef typename result_of<_Callable(_Args...)>::type result_type; ^

songyuanyao Over a year ago

@nateN What compiler are you using? I tried clang, it compiles fine. (Although got a link error.) rextester.com/YYSX61209

nateN Over a year ago

ahh...missed one detail...forgot to add the second parameter curlWrapper. Now it works! Thank you

songyuanyao Over a year ago

@nateN Glad to have been of help! Feel free to accept my answer if you feel it was useful to you. :-)

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