CODEWITHSUNDEEP
c++multithreading
Cpp Developer
Cpp Developer

Reputation: 51

C++ compiler error "cannot be thread-local because it has non-POD type”"

This statement:

___thread A a;

Generates this error:

cannot be thread-local because it has non-POD type

where A is 

class A{
       public:
               // function declaration
       private:
               // data members
};

I am trying this to compile on Linux, with command ogs includes & ogs mk. We have static threads i.e. before our application comes in we aware about the number of threads hence currently the work around is done with declaring the array of A i.e.

A a[Number of threads].

How can I fix this?

Upvotes: 5

Views: 2083

Answers (2)

Matthieu M.
Matthieu M.

Reputation: 300059

Unfortunately, there is no such thing as dynamic initialization (and destruction) of thread local resources in C++03 (which know nothing about threads, anyway).

In C++11, the thread_local storage keyword allows for dynamic initialization at the cost of runtime overhead (basically, equivalent to having a thread local static variable) and might thus be used without types with constructors.

In C++11, again, a constexpr constructor might be call for static initialization and should thus be compatible with the __thread specifier, provided your compiler implements it.

Upvotes: 1

SomeWittyUsername
SomeWittyUsername

Reputation: 18368

Assuming you use gcc, thread-local storage only supported for POD types, i.e. data-only structures. You can attempt to extract the data into a separate struct and make it thread local (actually, that's probably a good idea in any case because there is no much sense in making methods thread local).

Upvotes: 3

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