CODEWITHSUNDEEP
c++operating-system
hailinzeng
hailinzeng

Reputation: 995

Does the instances of a class still share the same static members between thread inside the same process?

That is what's the scope of sharing static members?

Upvotes: 0

Views: 154

Answers (3)

jogojapan
jogojapan

Reputation: 69997

Yes, static storage duration implies that the variable in question comes into existence when the process is started and is deallocated not before the end of the process. It is shared by all threads of the process, and accessing it can cause data races between the threads, just like with a global variable.

C++11 introduced a new storage duration specifier thread_local, the use of which implies that there is one instance of the variable in each individual thread. It is allocated when the thread begins.

Unfortunately none of the major compilers (GCC, Clang, VC++) has implemented this fully yet.

Upvotes: 2

Graeme
Graeme

Reputation: 4602

Yes, a class static member is shared across all instances of that class. It's scope can be restricted by marking it public, protected or private. If you are going to have multiple threads simultaneously accessing/mutating the static member then you will need to synchronise this access, e.g. via mutexes.

Upvotes: 2

Luchian Grigore
Luchian Grigore

Reputation: 258618

Yes, threading doesn't influence static storage. You can think of static members as globals. So modifying a static is not thread-safe, something to think about.

Upvotes: 1

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