Re: Thread safety
On Jun 6, 3:29 pm, arun.da...@gmail.com wrote:
Are the following thread safe:
1. Assuming Object is any simple object
Object* fn()
{
Object *p = new Object();
return p;
}
What does your compiler documentation say? If the compiler
doesn't specify the thread safety guarantees, nothing is thread
safe.
Note that many compilers specify this indirectly, e.g. by
claiming Posix conformance. And while Posix doesn't specify a
C++ binding, it's generally "understood" that new should have
the same guarantees as malloc. You can thus call the above from
multiple threads without any particular precautions.
2. is return by value thread safe?
If the compiler guarantees it, e.g. by being Posix conform. If
the type has a user defined copy constructor, of course, it
depends on what is in it. (The copy constructor for std::string
in g++ is currently NOT thread safe.)
3. int *p = new int
is this thread safe?
What does your compiler documentation say. If it is Posix
conformant (and presumably Windows conformant), then yes.
Note that you cannot talk about the thread safety of isolated
bits of code. Thread safety is a contract, to be met by both
parties. Unless the compiler/library documents what it
guarantees, and what your responsibilities are, then it is not
thread safe. If it documents the contract, it is, but it is up
to you to respect your end of it.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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