Re: [boost] [interprocess] Possible bug in offset_ptr

Subject: Re: [boost] [interprocess] Possible bug in offset_ptr
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2011-06-20 15:15:22

El 20/06/2011 9:14, Lars Hagstrom escribió:
> Hi,
>
> I reported a problem to the clang project about a problem I had with some
> release-compiled boost code.
> They're claiming it is a problem in offset_ptr, where the pointer arithmetic
> causes undefined behaviour according to the C++ standard.
> See: http://llvm.org/bugs/show_bug.cgi?id=10119
>
> This seems like a fairly major thing, if it is true.

It is true, yes, it always has been outside the standard, but worked for 
all compilers. For aggressive optimizers, the only solution is to 
disable inlining so that the compiler is forced to create stack 
offset_ptr variables with real addresses, that's the solution I took in 
trunk. Windows compilers had this inlining disabled since ages 
(__declspec(noinline)) and GCC was recently added 
(__attribute__((noinline))).

The fact is that with current standard, relative addressing is banned 
and I don't think there is workaround at all inside the standard. I 
think shared memory containers are not possible without visiting 
undefined behaviour.

Best,

Ion