Variables declared in F90 module and C routines

[jtache]

Dear CS users and CS team,

I searched for an answer to my problem in the forum and CS docs but I didn't find any, so I post it here.

I try to use some F90 variables (defined in mymodule() in cs_user_modules.f90) in a C routine (cs_user_mesh.c).
These variables are intialized at the beggining of the CS run by the use of cs_user_initialization.f90 routine.

I just declared my variable in cs_user_mesh C routine

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extern int myvar

and I try to print it with

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bft_printf("myvar = %6i\n", myvar);

Compiler complains about a "nested extern declaration of myvar" in cs_user_mesh.c (this could be fair as myvar will be known after linking of objects files) and compilation stops with this message :

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cs_user_mesh.c:(.text+0x24) : référence indéfinie vers « myvar»
collect2: error: ld returned 1 exit status

This seems to be a linking problem, so it's probably about a missing declaration of mymodule() or a bad declaration of my variable.

Can you help me and indicate how I can properly include my module in the C routine, just like I "use mymodule" in F90 routines?

Thanks for feebacks!

Jeremie

[Yvan Fournier]

Hello,

In which module is "myvar" defined ? The full (linkage) name is usually a compound name including that of the module.

To avoid issues, the cleanest solution is to use iso_c_bindings to access the variable (and/or to use a function to access it).

It may be simpler to define the variable in C, and access it using a Fortran pointer (check for example how imrgra and anomax, defined in optcal.f90, and linked in cs_parameters.c using cs_f_space_disc_get_pointers).

Best regards,

Yvan