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barrera
Joined: 29 Apr 2020 Posts: 3
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Posted: Wed Apr 29, 2020 7:06 pm Post subject: Calling A FORTRAN DLL From Excel & VBA |
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Using:
Windows 8.1 © 2013
64 bit OS, x64-based processor
MS Office 2013 x64
Download the example from https://myengineeringworld.net/2014/03/fortran-dll-excel-vba.html
Copy the “Calling A FORTRAN DLL From Excel & VBA.xlsm” to the folder ..\MySample\Release\x64
Open the .xlsm
Click on the “Enable Content” button
In VBA window, add “PtrSafe” to both Public Declare…
Save and Close
As seen in https://www.silverfrost.com/32/ftn95/ftn95_personal_edition.aspx just downloaded the compiler FTN95 Personal Edition (FTN95PE) version 8.61 from http://www.ftn95.co.uk/ftn95/ftn95-8.61/ftn95_personal.exe
Run "C:\Program Files (x86)\Silverfrost\FTN95\plato.exe"
File > New > Project:
Project Type: Fortran DLL
Name: MySample
OK
In “Project Explorer”, right click on “Source Files”, click on “Add New Item”
Type: Free format Fortran file
Name: MyCode
And paste the content of the downloaded MyCode.f90 in a new .f95 source file
Configuration: Release Platform: x64
Build > Build
So far so good:
“Compiling file: MyCode.f95
C:\Users\BarRErA\Documents\MySample\MyCode.F95(17) : warning 197 - Variable C has been declared but not used
C:\Users\BarRErA\Documents\MySample\MyCode.F95(17) : warning 197 - Variable D has been declared but not used
C:\Users\BarRErA\Documents\MySample\MyCode.F95(51) : warning 197 - Variable I has been declared but not used
Compilation completed with no errors.
Linking...
Creating dynamic link library C:\Users\BarRErA\Documents\MySample\Release\x64\MySample.dl”
When opening the .xlsm, Excel crashes or a exception is thrown.
“FATAL ERROR > Silverfrost exception handler has failed”
Commenting the FRICTIONFACTOR on the .f95 code, compiling again, then going to Excel > tab Sub > clicking RUN (i.e. running the VBA Sub CallDoubleArray()), it works. The problem is with the function call.
I have no clue about what to do. It is my first contact with FORTRAN, I’m an engineer that wants to translate some thermodynamic calculations from VBA to Fortran. |
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barrera
Joined: 29 Apr 2020 Posts: 3
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Posted: Wed Apr 29, 2020 7:13 pm Post subject: Exception Report |
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opening via Plato (32 bit) and compiling it again, I got this log:
"Silverfrost 64-bit exception report on C:\Program Files\Microsoft Office 15\Root\Office15\EXCEL.EXE Wed Apr 29 15:08:57 2020
Unknown exception (c004f012) at address 7ffd8cec908c
Within file KERNELBASE.dll
In RaiseException at address 6C
In RpcRaiseException at address 51
Within file RPCRT4.dll
In RpcRaiseException at address 14
In NdrClientCall3 at address F6A
In NdrClientCall3 at address FE
Within file sppc.dll
In SLUnregisterPlugin at address 993
In SLGetPolicyInformation at address 63
In Ordinal7162 at address 12B8
Within file mso.dll
In Ordinal7162 at address 11B4
In Ordinal7162 at address 14C0
RAX = 000000391254e420 RBX = 00000000c004f012 RCX = 00007ffd8ecec750 RDX = 0000000000000000
RBP = 0000000000000003 RSI = 0000000000000000 RDI = 000000391254eaf0 RSP = 000000391254e670
R8 = 000000391254e420 R9 = 00007ffd66dc1438 R10 = 00007ffd8ecfe844 R11 = 000000391254e420
R12 = 0000000000000000 R13 = 0000000000000001 R14 = 000000391254ef28 R15 = 000000391254f228
7ffd8cec908c) mov_q RCX,[c0+RSP]" |
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Moji
Joined: 30 Sep 2020 Posts: 27
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Posted: Fri Apr 23, 2021 6:01 pm Post subject: |
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I have also similar problem in calling 64-Bit Fortran dlls in 64-Bit Excel.
I used this simple Fortran code:
Code: |
DOUBLE PRECISION FUNCTION test_code1(myarg1, myarg2)
DOUBLE PRECISION myarg1, myarg2
test_code1 = myarg1 + myarg2
END
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I removed all the ftn95 options from config and compiled the code just by using /64 option (ftn95 test_code1.f90 /64) and linked the dll with slink64. The created dll was then transferred into the C:\Windows\System32 directory of another computer, in which 64-bit Excel is installed.
Next, in Excel(64-Bit) I created this VBA code:
Code: |
Private Declare PtrSafe Function TEST_CODE1 Lib "test_code1.dll" (ByRef arg1 As Double, ByRef arg2 As Double) As Double
Public Function test_sum1(arg1 As Double, arg2 As Double) As Double
test_sum1 = TEST_CODE1(arg1, arg2)
End Function
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and save the file with *.xlam extension. I opened Excel again and added the *.xlam file as an Add-in.
Now everything is prepared to call test_sum1 function which interacts with Fortran dll. The Function works and the results are correct, but:
- When you try to insert a diagram, excel crashes.
Or - When you save your test file and open it again, after a while you get an access violation error message.
I am using Windows 10 Enterprise LTSC - Version:1809, Microsoft Excel 365 Version 2103, FTN95 Version 8.71.0
Last edited by Moji on Thu Jun 24, 2021 9:18 am; edited 1 time in total |
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Moji
Joined: 30 Sep 2020 Posts: 27
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Posted: Wed Jun 09, 2021 12:45 pm Post subject: |
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I am writing this post, to get some help regarding calling 64-Bit Fortran subroutines/functions in Excel.
In the previous post, I explained the process that I used and the corresponding error.
I think it is a compiler bug, but I am not sure about it. Therefore, if you have any experience in calling 64-Bit DLLs in 64-Bit Excel, I would be happy to hear about it. |
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mecej4
Joined: 31 Oct 2006 Posts: 1840
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Posted: Wed Jun 09, 2021 2:14 pm Post subject: |
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Why do you think that your problem is caused by a compiler bug? Here is evidence to the contrary. The DLL that you built using FTN95 on the Fortran source has a well-defined API. Here is a C program that calls the function in the DLL using that API, and runs with no errors and prints the correct result.
Code: | #include <stdio.h>
extern double TEST_CODE1(double *a, double *b);
int main(){
double x = 10.2, y = 9.8;
double z = TEST_CODE1(&x, &y);
printf("Z = %e\n",z);
} |
I did the following:
1. I built the DLL using your source code, and the commands
Code: | ftn95 /64 test_code1.f90
slink64 /dll test_code1.obj /exportall
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2. I built an import library for Visual C using the following DEF file:
Code: | LIBRARY TEST_CODE1
EXPORTS
TEST_CODE1 |
using the command
Code: | lib /def:test_code1.def /machine:x64 |
3. I compiled and linked the C program using the command
Code: | cl tcode.c test_code1.lib |
4. Running the resulting EXE produced the expected result.
I am not an Excel user and so I do not know if the version of Excel that you use does follow the same API used in my example and as declared in your VBA code. |
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Moji
Joined: 30 Sep 2020 Posts: 27
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Posted: Wed Jun 09, 2021 4:55 pm Post subject: |
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Hi mecej4,
thank you so much for your reply.
As I mentioned in my first post, Excel can also call Fortran functions and the results are correct, but Excel crashes later on, as you try to insert a diagram, or when you save the project file, close it and open the project again.
There is a subtle difference between your C program and my Excel case. You start your program, call the fortran function, present the result and end it afterwards. However in my case, Excel should be able to keep working after calling the Fortran function without crashing. In other words, if I close Excel after getting the results (like your C program), nobody would notice that something is wrong.
"Why do you think that your problem is caused by a compiler bug?"
I also managed to call Fortran functions from a C++ program and later on in a C++ DLL, similar to what you did. But then as I imported the C++ DLL into MATLAB software, MATLAB crashed after a while with a silverfrost access violation error message. Here is the link to that topic.
Since these two 64-Bit cases are compeletly independent and both end up with access violation error, I thought that maybe it is a compiler bug. I should also mention that with 32-Bit Fortran DLLs and 32-Bit Excel, everything works fine. |
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Thomas
Joined: 18 Feb 2005 Posts: 47 Location: Gummersbach, Germany
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Posted: Thu Jul 15, 2021 11:49 am Post subject: Calling a DLL developed with FTN95 from Excel 64 bit |
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The request to call a DLL developed with FTN95 from Excel 64 bit becomes more and more urgent for my company. Some of our customers roll out Office 64 bit and we cannot support this version.
We cannot say it's a problem with FTN95; we can also not state it's an MS Office problem. Instead it seems to be a problem with the interface or interaction between both components.
Description:
The DLL calls from Excel work initially, i.e. we get the correct results of the functions. After some time, however, Excel behaves strange and stops working properly. The Excel response is not constantly the same, sometimes it don't give any response and one has to cancel the process with the Windows task manager. Sometimes an error message appears as described below:
Code: | Access violation (c0000005) at address aa6c1
Within file SALFLIBC64.DLL
in prepare_register_details(<ptr>char) at address 7a
in details_box(void) at address 3b
Within file CLEARWIN64.DLL
In _set_mg_return_value at address 8C3F
...
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Who can possibly share his knowledge how to call a FTN95 based DLL from Excel 64 bit? Who has sucessfully resolved this issue? _________________ Thomas |
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PaulLaidler Site Admin

Joined: 21 Feb 2005 Posts: 7774 Location: Salford, UK
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Posted: Thu Jul 15, 2021 12:39 pm Post subject: |
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Thomas
prepare_register_details and details_box are functions within salflibc64.dll. They were called when processing an exception that was raised within the ClearWin+ function _set_mg_return_value.
_set_mg_return_value is the internal name for set_mg_return_value@ which in theory was called from your Fortran code.
If you (or someone else) can provide code for a very simple project that demonstrates the failure then (given time) we might be able to investigate further. |
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Thomas
Joined: 18 Feb 2005 Posts: 47 Location: Gummersbach, Germany
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Posted: Tue Aug 10, 2021 2:43 pm Post subject: Calling Fortran functions in Matlab (64-bit) and Office (64) |
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Dear forum users, dear Silverfrost team,
The demand for support regarding FTN95 integration in MS Excel is really not new. Already in October 2012, i.e. 9 years ago, a sent the following request to the "General" forum:
Thomas wrote: | Searching for advice, how to integrate FTN95 DLLs into 64 bit applications, I became aware of the forum's discussion about the interst in a 64 bit version of FTN95.
I can agree with many of the other members: Yes, there is a demand for a 64 bit version.
My background/characteristics:
- Using Salford/Silverfrost products for a very long time (FTN77, DBOS).
- Large amount of existing Fortran source code.
- Extensive use of ClearWin.
- Integration of DLLs, developed with FTN95, into other applications like MS Office, Delphi, VB.
Recently I had appreciated the development of DBOS to overcome the limitations of a 16 bit operation system and to make more memory available for development and application. I saw - and I am still seeing - Salford/Silverfrost as a front runner to support fortran programmers with application tools which are not directly related to a specific environment reagarding hardware and software and which are designed to fulfill the programmer's needs.
Today we are faced to the problem that the 64 bit development is progressing. More and more of our customers may use 64 bit versions of software products. Although 32 bit seems to be the default for e.g. MS office, 64 bit versions are available and some companies may decide to make use of them.
Therefore a request for 64 bit versions of DLLs will arise. I would prefer to have a solution based on Silverfrost FTN95 or FTN20xx. If there is a prospect of availability within reasonable time, I would appreciate. Otherwise I have to look for alternatives. |
I'm still wondering, if my company, Steinmüller Engineering with Moji as co-author, is alone in the FTN95 community to be faced with this problem. _________________ Thomas |
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PaulLaidler Site Admin

Joined: 21 Feb 2005 Posts: 7774 Location: Salford, UK
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Posted: Wed Aug 11, 2021 7:43 am Post subject: |
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Thomas
Thank you for this enquiry.
I have carried out a brief initial investigation based on code supplied by Moji. If the failure reported by Moji is due to a fault in FTN95 then it may relate to the calling convention that is used (the passing of arguments on a stack and the cleaning of this stack after the call).
For Moji calls to FTN95 from Exel work initially but there is a crash after a few calls.
It would be helpfully to know if this behaviour (when calling from Exel) is experienced by others. Also it would help to know if the same problem arises when a stand alone Visual Basic program calls into an FTN95 DLL. |
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Moji
Joined: 30 Sep 2020 Posts: 27
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Posted: Wed Aug 11, 2021 12:14 pm Post subject: |
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Paul,
As you asked for it, I created a stand alone 64-Bit Visual Basic program. This program calls a function from a FTN95 DLL and returns the result.
The program works fine and without any errors. |
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PaulLaidler Site Admin

Joined: 21 Feb 2005 Posts: 7774 Location: Salford, UK
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Posted: Wed Aug 11, 2021 12:42 pm Post subject: |
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Moji
Please display the code for VB, for the Fortran and the SLINK64 script for the DLL.
The fact that it works for VB suggests that FTN95 is functioning correctly. |
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Moji
Joined: 30 Sep 2020 Posts: 27
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Posted: Wed Aug 11, 2021 1:36 pm Post subject: |
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Here is the Fortran Code (test_code1.f90):
Code: | DOUBLE PRECISION FUNCTION test_code1(myarg1, myarg2)
DOUBLE PRECISION myarg1, myarg2
test_code1 = myarg1 + myarg2
END |
The code is compiled using :
Code: | ftn95 test_code1.f90 /64 /-check |
and linked by:
Code: | slink64 /file:test_code1.dll test_code1.obj |
The VB program is a windows Form program consisting of a form with 2 input boxes (TextBox1 and TextBox2), an output box (TextBox3) and a button (Button1):
Code: | Public Class Form1
Private Declare Function TEST_CODE1 Lib "test_code1.dll" (ByRef MYARG1 As Double, ByRef MYARG2 As Double) As Double
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim a As Double = 0
Dim b As Double = 0
If IsNumeric(TextBox1.Text) Then a = CDbl(TextBox1.Text)
If IsNumeric(TextBox2.Text) Then b = CDbl(TextBox2.Text)
TextBox3.Text = TEST_CODE1(a, b)
End Sub
End Class |
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JohnCampbell
Joined: 16 Feb 2006 Posts: 2506 Location: Sydney
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Posted: Thu Aug 12, 2021 2:27 am Post subject: |
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I am also interested in being able to transfer information between a 64-bit Fortran program and a .xlsx (multi-tab) file.
If a template of basic functionality can be demonstrated with FTN95 /64, that would be a useful achievment, worthy of a section in ftn95.chm ! |
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PaulLaidler Site Admin

Joined: 21 Feb 2005 Posts: 7774 Location: Salford, UK
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Posted: Thu Aug 12, 2021 6:53 am Post subject: |
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John
For the moment you can use the information in the help files for 32 bit FTN95 with Visual Basic. This information is also in the Forum Knowledge Base.
Except one doesn't use F_STDCALL for 64 bits and a call to LoadLibrary is probably not needed. |
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