Re: Shared memory between Visual Studio build and MinGW build

From: Da Xu (djsignal7_at_[hidden])
Date: 2020-03-03 01:43:31

 Thank you for the reply. 
Right now, I am actually stuck in Boost's segment manager. Its own data structure got scrambled in the memory. I haven't even gotten to where my own data structure gets read.
If I do go with the bare metal approach,  I will definitely keep these advice in mind.

Da.
    On Monday, March 2, 2020, 06:33:55 PM EST, Gavin Lambert via Boost-users <boost-users_at_[hidden]> wrote:  
 
 On 3/03/2020 08:37, Da Xu wrote:
> Thank you guys. Yah, the problem is that the pieces I am writing are all 
> DLLs. And of course, gcc DLL and Msvc DLLs aren't compatible. Therefore, 
> I HAVE to use two compilers.
> 
> So, clang might produce data structure layout that might be compatible 
> with gcc?

If you confine your shared memory interface to POD types that use 
well-known-sized fields, then most compilers will produce a compatible 
binary layout.  (With a few quirks to watch out for, such as default 
padding and potentially different sizes for "int", "long", "size_t", 
"time_t", etc.  It doesn't hurt to explicitly static_assert(sizeof(T) == 
known_constant) in both compilers.)

It's when you introduce non-POD C++ types that you typically run into 
trouble.  For example, library types such as std::string are not 
guaranteed to have equivalent binary layout across different compilers 
(or even different compiler versions).
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