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Date: Fri, 23 Nov 2012 09:37:00 -0000
Message-ID: <CAH6eHdTwgVkPyYdV3LQWG08THZjqi56DoeRswUi8VX=o6tGjAA@mail.gmail.com>
Subject: Re: [C++] anonymous struct linkage
From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: LAMOME Julien CS-SI <julien.lamome-cs-si@irsn.fr>
Cc: gcc-help@gcc.gnu.org
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On 23/11/2012, LAMOME Julien CS-SI <julien.lamome-cs-si@irsn.fr> wrote:
> a minimum code to show the problem :
> toto.F :
>       subroutine toto()
>       implicit none
>       real*8 variable
>       common /demof/variable
>
>          print*,'Fortran variable=',variable
>       end
>
> toto.cc:
> #include <iostream>
> struct {double variable;}demof;
> extern "C" void toto();
> int main()
> {
> 	demof.variable=3.14159;
> 	std::cout<<"C++  variable = "<<demof.variable<<std::endl;
> 	toto();
> 	return 0;
> }
>
> * Gcc 4.1 give me :
> C++  variable = 3.14159
>  Fortran variable= 3.14159000000000
> * Gcc 4.6 give me:
> C++  variable = 3.14159
>  Fortran variable= 0.00000000000000
>
> Yours differents solutions work, but I would prefer to use an option to have
> the old behavior. Because, I have 163 files with anonymous strut to modify.
> And, each file require special attention because struct are linked, or not,
> with a COMMON, and COMMON are not necessary include in source, etc.
> So, if it isn't possible to use an option, I will have a lot of work now.
> Else I could modify  progressively.



The old behaviour does not conform to the C++ standard.

I don't think there is any option to restore the old non-conforming behaviour.