In the meantime I found out what is causing the problem. There seems to be a bug in the connection from gfortran to UCRT (Microsofts universal C runtime, that ships with Windows 10 and 11). If I switch to a compiler that uses MSVCRT (Microsoft Visual C runtime, an older library, but still available) the problem disappears.
The port of the mingw64 I use comes in both flavors. So using the MSVCRT version solves it. Juergen Am 18.02.25 um 13:56 schrieb Jürgen Bausa:
I am trying to compile some C and fortran code inserted into a dll to be called by Excel. However, on each successful Fortran open statment Excel crashes without any message. Everything else works perfectly so I am sure the Excel/DLL interface works in principle. I also found out, that the crash only happens if the open (for reading, STATUS='OLD') statment is successful. So if I delete the file to open, the program runs fine. I then tried to call the same routine in the dll from a C program. That works fine in both cases (file to open exists or does not exist). As the problem arose in a very big project I tried to write a very simple version that results in the same problem (see below). At the moment I think the problem is most likely caused by libgfortrans implementation of open. It seems to be somehow incompatible with Excel. Is there a way to debug this? I was thinking about compiling my own ligfortran and add some debug code to find out, where exactly the problem is. Any other suggestions? I am using Windows 11 and Excel 365 (both 64 Bit) and GCC 14.2.0 WIN64 from winlibs (https://winlibs.com/). Here is my example: f77open.f --------------------------------------- SUBROUTINE F77OPEN(STATUS) INTEGER STATUS STATUS=0 OPEN (UNIT=10, FILE='C:\Users\ztbau\btx.dat', 2 ERR=100, IOSTAT=IOERR, STATUS='OLD') CLOSE(10) RETURN 100 STATUS=2 RETURN END ------------------------------------------------- f77open.h --------------------------------------- #include <stddef.h> #ifdef __cplusplus #include <complex> #define __GFORTRAN_FLOAT_COMPLEX std::complex<float> #define __GFORTRAN_DOUBLE_COMPLEX std::complex<double> #define __GFORTRAN_LONG_DOUBLE_COMPLEX std::complex<long double> extern "C" { #else #define __GFORTRAN_FLOAT_COMPLEX float _Complex #define __GFORTRAN_DOUBLE_COMPLEX double _Complex #define __GFORTRAN_LONG_DOUBLE_COMPLEX long double _Complex #endif /* Prototypes for external procedures generated from f77open.f by GNU Fortran (MinGW-W64 x86_64-ucrt-posix-seh, built by Brecht Sanders, r3) 14.2.0. Use of this interface is discouraged, consider using the BIND(C) feature of standard Fortran instead. */ void f77open_ (int *status); #ifdef __cplusplus } #endif --------------------------------------------------- dlltest2.c ---------------------------------------- #include <windows.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> #include "f77open.h" int WINAPI dlltest2() { int status=0; f77open_ (&status); return status; } ---------------------------------------------------- to compile I use the following commands: ---------------------------------------------------- gcc -march=native -fno-diagnostics-color -Wall -c -o dlltest2.o dlltest2.c gfortran -march=native -fno-diagnostics-color -Wall -c f77open.f gcc -march=native -fno-diagnostics-color -shared -Wl,--add-stdcall-alias dlltest2.o f77open.o -o dlltest2.dll -lgfortran ---------------------------------------------------- Regards, Juergen
