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.
-----Message d'origine-----
De : Jonathan Wakely [mailto:jwakely.gcc@xxxxxxxxx]
Envoyé : jeudi 22 novembre 2012 22:07
À : LAMOME Julien CS-SI
Cc : gcc-help@xxxxxxxxxxx
Objet : Re: [C++] anonymous struct linkage
On 22 November 2012 21:03, Jonathan Wakely wrote:
> On 22 November 2012 15:44, LAMOME Julien CS-SI
> <julien.lamome-cs-si@xxxxxxx> wrote:
>> Hi,
>> we have a code mixing C++ and Fortran 77. In fortran, we have some COMMON like :
>> COMMON / DEMOF/VARIABLE
>> Which are include in fortran source file like this :
>> #include <demof.include>
>>
>> We link with C++ code like this :
>> struct { double variable}demof ;
>>
>> The problem is :
>> Between gcc 4.3 and gcc 4.6, the linkage of demof (in C++) change from global to local. This breaks the link between C++ and fortran.
>>
>> How can I restore the global linkage in gcc 4.6 ?
>
> Give the type a name:
>
> struct D { double variable; } demof;
>
> Problem solved.
Alternatively, give it C language linkage:
extern "C" {
struct { double d; } demof;
}
