Error when calling c++ dll from delphi

Question

I am trying to use create a c++ wrapper (using MSVS2013) for some fortran code. The wrapper is supposed to be called from DELPHI (old code created in DELPHI 5 - which I cannot touch). (DELPHI -> C++ dll -> fortran dll) The aim is that some data struct s ( record in delphi) with int 's and double 's and double[] 's are passed from delphi to fortran for calculations. The c++ dll -> fortran is no problem - that I have tested with another c++ executable. It works. The problem is when delphi calls c++ and c++ calls fortran. Then I get an error that says

Project "myDelphiProject.exe" raised exception class EZeroDivide with message 'Floating point division by zero'.

There is no problem calling the c++ wrapper if the call to fortran does not happen. I have tested and confirmed that all variables get through between delphi and c++. Calling convention is set to cdecl .

Simplified code: Delphi

interface
rec1 = record
  var1,var2: double;
  end;
procedure myCppWrap(record1: myrecord); cdecl; external 'mycppwrap.dll' name '_myCppWrap'
implementation
procedure MyDelphiFunc();
var
 ...
begin
 myCppWrap(rec1)
 ...

Simplified c++ code:

struct rec1
{
  double var1,var2;
}
extern "C" __declspec(dllexport) __cdecl myCppWrap(rec1 r1);
extern "C" *myFortranSub(double *varF1,double *varF2);

In short: DELPHI -> C++ works, C++ -> Fortran works, DELPHI -> C++ -> Fortran does not work.

Does anyone have any idea of what is wrong?

---

EDIT: OK.. so I have managed to narrow it down: I have division by zero that results in infinity (which is a correct internal result with the given input - this is not direct output from fortran dll). This goes well when being called by c++ but not from delphi when the fortran dll is compiled using default release settings. However it does work when using debug settings, both in c++ and delphi. I output variables to a text file (before and after division) for verification and in all 4 cases the divisor is 0 and the result is 'inf' in the three cases that goes well. Both in debug and release mode I have the same setting for floating point exception handling "Produce NaN, signed infinities, and denormal results".

This turns out to be more of a compiler setting/flag problem than coding...

Anyone have any experience with this?? (I am working on a small and verifiable code piece)

Answer 1

So following David Heffeman 's advice... adding

use ifcore

and

fpe_old_flags = FOR_SET_FPE(0)

in the beginning of the code solved it. Thanks a lot David!