Thank you for your response!

i write C++ function with extern "C" commend, then call the C function in Fortran code.

This is the process what i did

1. compile C++ code, then make .dll, .obj, .lib file

2. then write Fortran code with INTERFACE for C++ code. and also include line that calling dll file of C function

3. then modified to read the .lib file generated by the abaqus .env file

4. but there is error [LNK1104] which cannot open .lib file

so i think my code about C and Fortran is adequate, but some abaqus environment is wrong.

i really try it a lot, but pretty difficult..

If you know anything about modifying the .env file, i would greatly appreciate it.

Yes, it's possible to call a C function within a Fortran subroutine, including in Abaqus user subroutines written in Fortran. This process involves interfacing between Fortran and C, commonly referred to as "mixed-language programming" or "interlanguage calling."

Mohit Tiwari

Thank you for your response!

I really did it a lot, but i think the problem i face is configuring 'abaqus_v6.env' file.

so i edit 'abaqus_v6.env' file to link with cpp library file.

the linking another library file is editing 'link_sl' on env file.

so i add my cpp library directory and file name. (see below)

link_sl=['LINK', '/nologo', '/INCREMENTAL:NO', '/subsystem:console', '/machine:AMD64', '/NODEFAULTLIB:LIBC.LIB', '/NODEFAULTLIB:LIBCMT.LIB',

'/DEFAULTLIB:OLDNAMES.LIB', '/DEFAULTLIB:LIBIFCOREMD.LIB', '/DEFAULTLIB:LIBIFPORTMD', '/DEFAULTLIB:LIBMMD.LIB',

'/DEFAULTLIB:MSVCRT.LIB', '/DEFAULTLIB:kernel32.lib', '/DEFAULTLIB:user32.lib', '/DEFAULTLIB:advapi32.lib', '/FIXED:NO','/LIBPATH:"D:/KEB/01.k9/02.present/22.vuamp/01.test1/vuamp_vdload_C5"','test16.lib', '/dll', '/def:%E', '/out:%U', '%F', '%A', '%L', '%B', 'oldnames.lib', 'user32.lib', 'ws2_32.lib',

'netapi32.lib','advapi32.lib']

but the error occur with 'can't open teset16.lib file'

do you have any i dear or solution about that?

The error message "can't open test16.lib file" indicates that the linker cannot find the test16.lib file in the specified location. Let's try to troubleshoot this issue step by step:

Check File Location:

Ensure that test16.lib is indeed located in the directory D:/KEB/01.k9/02.present/22.vuamp/01.test1/vuamp_vdload_C5.

Verify the spelling of the file name; ensure there's no typo like "teset16.lib" instead of "test16.lib".

Absolute vs. Relative Paths:

It's always a good practice to use absolute paths in configuration files, especially when linking libraries. The path you've provided seems to be absolute, but double-check to ensure it's correct.

File Permissions:

Ensure that you have the necessary permissions to access test16.lib. It's possible that the file is in the correct location, but the user or process trying to access it doesn't have the required permissions.

Check the Library File:

Verify that test16.lib is not corrupted. If you have a backup or another version, try linking against that to see if the issue persists.

LIBPATH Syntax:

The /LIBPATH argument specifies a directory to search for libraries. Ensure there's no typo or syntax error in this line: '/LIBPATH:"D:/KEB/01.k9/02.present/22.vuamp/01.test1/vuamp_vdload_C5"'.

Other Directories:

Check if there are other directories in the abaqus_v6.env file that are also being searched for libraries. It's possible that the linker is looking in another directory that has an older or different version of test16.lib.

Environment Variables:

Sometimes, paths and library locations can be set using environment variables. Ensure that no environment variable is overriding the settings in your abaqus_v6.env file.

Clean and Rebuild:

If you're building a project, sometimes old build artifacts can cause issues. Clean or delete any old build files and try building/linking again.

Linker Version:

Ensure that the linker version is compatible with the library you're trying to link. If test16.lib was built with a different compiler version or settings, it might not be compatible.

Consult Documentation:

Check Abaqus documentation or any guidelines you're following to ensure you've set up the abaqus_v6.env file correctly.

If you've tried the above steps and the problem persists, consider reaching out to Dassault Systèmes' support or any relevant forums where other Abaqus users might have faced similar issues.

Thats all i could think . Regards and all the best sir .

Hi Kim Eubin

Yes, it is possible to call a C (or C++) function from within an Abaqus user subroutine written in Fortran, and this can be done on a Windows environment. The process involves creating a mixed-language program. Here's a general overview of the steps involved:

1. **Write the C Function**: Make sure the function you want to call from Fortran is correctly defined. When declaring functions that you plan to call from Fortran, it's common to use the `extern "C"` linkage specification to ensure C linkage, not C++ linkage.

C Program :

extern "C" {

void my_c_function(...);

}

```

2. **Compile the C Code**: Use a C/C++ compiler to compile the code into an object file. On Windows, you can use a compiler like Visual Studio's `cl` or MinGW's `gcc`.

3. **Interface in Fortran**: In the Fortran subroutine, you'll need to declare the C function using an `INTERFACE` block, and the function can then be called like any other Fortran routine.

FORTRAN PROGRAM :

INTERFACE

SUBROUTINE my_c_function(...) BIND(C, NAME='my_c_function')

...

END SUBROUTINE

END INTERFACE

```

4. **Compile the Fortran Code**: Compile your Fortran code (which contains the Abaqus subroutine) into another object file.

5. **Linking**: When you have both object files (from the C and Fortran code), you need to link them together to create the shared library that Abaqus will use. This step may require including certain libraries that both your C++ compiler and Fortran compiler depend upon.

6. **Abaqus Execution**: When running Abaqus, you'll need to make sure it can find your shared library. This might involve setting certain environment variables or specifying paths within Abaqus.

### Important Tips:

- **Compiler Consistency**: Ensure that the Fortran and C/C++ compilers are compatible. This means they should ideally come from the same vendor or, at the very least, be known to produce compatible object code.

- **Calling Convention**: Fortran and C use different calling conventions. Ensure consistency in how arguments are passed and returned.

- **Name Mangling**: C++ compilers "mangle" function names, which can cause linking errors. Using `extern "C"` avoids this by ensuring C linkage.

- **Windows Specifics**: On Windows, there are additional considerations, especially around Dynamic Link Libraries (DLLs) and the `__declspec(dllexport)` and `__declspec(dllimport)` directives. Familiarize yourself with these if you encounter linking issues.

While the process can be intricate, especially the first time you attempt it, it's entirely feasible. Ensure you have a clear understanding of both your Fortran and C compilers and that you meticulously manage the intermediate files and final linked shared libraries.

Josnier Ramos Guardarrama

Thanks for your answer!! i did it already before, but the solution you write makes me check it again!

Yousef Bahrambeigi

Thanks for your answer!

i did it already, but i think when compiling abaqus fortran code, it must be linked with c++ library file...

i tried everything above the answer, but it never works...

so i show my user-subroutine code and c++ code.

please check my codes and whether there is something wrong..

subroutine code---------------------------------------------------

!c user amplitude subroutine

!c

subroutine vuamp(ampName, time, ampValueOld, dt,nprops,props, nSvars, svars, lFlagsInfo,&

nSensor, sensorValues, sensorNames, jSensorLookUpTable,&

ampValueNew,&

lFlagsDefine,&

AmpDerivative, AmpSecDerivative, AmpIncIntegral)

USE, INTRINSIC :: ISO_C_BINDING

include 'vaba_param.inc'

parameter (iStepTime = 1,&

iTotalTime = 2,&

nTime = 2)

parameter (iInitialization = 1,&

iRegularInc = 2,&

ikStep = 3,&

nFlagsInfo = 3)

parameter (iComputeDeriv = 1,&

iComputeSecDeriv = 2,&

iComputeInteg = 3,&

iStopAnalysis = 4,&

iConcludeStep = 5,&

nFlagsDefine = 5)

dimension time(nTime), lFlagsInfo(nFlagsInfo),&

lFlagsDefine(nFlagsDefine),&

sensorValues(nSensor),&

sVars(nSvars)

character*80 sensorNames(nSensor)

character*80 ampName

dimension jSensorLookUpTable(*)

interface

function kadd(a, b) bind(C, name="kadd") result(res)

use, intrinsic :: iso_c_binding

real(c_double), intent(in), value :: a, b

real(c_double) :: res

end function kadd

end interface

!

!***************************************************************

! Variables for C++ function call

real(c_double), target :: x, y

real(c_double), pointer :: px, py

real(c_double) :: result

x = 3.0_c_double

y = 4.0_c_double

px => x

py => y

lFlagsDefine(iComputeDeriv) = 1

lFlagsDefine(iComputeSecDeriv) = 1

displacement = vGetSensorValue('SENSOR', jSensorLookUpTable, sensorValues)

if (ampName(1:3) == 'AAA') then

if (lFlagsInfo(iInitialization) == 1) then

ampValueNew = ampValueOld

svars(1) = 0.0

svars(2) = 0.0

else

time=time(iStepTime)

ktime=time(1)

!***************************************************************

! C++ FUNCTION

!***************************************************************

x = 3.0_c_double

y = 4.0_c_double

result = kadd(x, y)

write(*,*) 'kFORCE=',result

!***************************************************************

ampValueNew = 0.0d0

svars(1)=displacement

end if

end if

return

end

subroutine code end---------------------------------------------------

C++ code--------------------------------------------------------------

// test16.cpp : Defines the exported functions for the DLL application.

//

#include "stdafx.h"

extern "C" {

__declspec(dllexport) double __cdecl add(double* a, double* b) {

return *a + *b;

}

}

C++ code end----------------------------------------------------------