Re: [PATCH 1/9] interface additions for the C thread implementation

[Jens Gustedt <jens.gustedt@inria.fr>]

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Am Sonntag, den 07.09.2014, 14:05 +0400 schrieb Alexander Monakov:
> On Sun, 7 Sep 2014, Jens Gustedt wrote:
> > > > For the C++ API/ABI, these also are different types, now, with type names
> > > > (that are used for name mangling, e.g) as listed above.
> > > > 
> > > > Somebody better versed in C++ could perhaps contribute code that
> > > > overloads the comparison and assignment operators such that a compilation
> > > > that tries to compare or copy these types fails.
> > > 
> > > I'm not sure what you meant by this last paragraph.
> > 
> > AFAIR in C++ there are ways to inhibit usage of copy assignment by
> > declaring some "operator=" function that is never defined. But my C++
> > has really become rusty.
> 
> There's no need to do that since those are unrelated structs, and therefore no
> operator== and operator= are available in the first place.  You also can't do
> that in C (but in C++ you get an error rather than a warning when trying
> to assign pointers).

This is not about assignment between different types and also not for
pointers but for the struct themselves.

With the current C threads version the following is a priori allowed,
but shouldn't:

mtx_t a, b;
mtx_init(&a, mtx_plain);
b = a;

This "works" in C and in C++.

The corresponding code in pthreads would be UB.

Jens

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