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Mixing Fortran and C

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Carola Bloemer_1
Occasional Contributor

Mixing Fortran and C

I have a program code mixing Fortran77 and C. I can compile each source file to an o-file using the aCC and Fortran 90 compiler but the linking of the program fails.

Here the code:

>>>>>>>>>> main.c: <<<<<<<<<<
int main(unsigned int argc,char **argv)
extern void halloc(void);
extern void hallof(void);
/* c calls fortran: */
/* c calls c: */
void halloc(void){ printf("hallo cn"); }

>>>>>>>>>> help.f: <<<<<<<<<<
subroutine hallof
print *,"HALLO F"
C.....fortran calls c:
call halloc()

I tried different ways to compile this test-program. Reading the online-manuals I discover the tip to link with "-lisamstub". This has no effect. Here how I tried to compile and link the program:
f90 -c help.f
aCC -c main.o
aCC -o test main.o help.f -lisamstub
Can anybody help me solving this problem?

Thanking you in advance.
Stefan Farrelly
Honored Contributor

Re: Mixing Fortran and C

You havent specificed the error you get when trying to link it. Can you ?

Meanwhile you could try;
aCC -o test main.o help.f -l:isamstub

Im from Palmerston North, New Zealand, but somehow ended up in London...
Andy Bennett
Valued Contributor

Re: Mixing Fortran and C

The problem with is that you've switched from using a C compiler (cc) to a C++ one (aCC). If you have no genuine C++ code it is probably unecessary to switch this compiler since cc is still a fully supported and current product. Your unresolved symbols should vanish by doing this alone. You may need libraries "-lF90 -lcl" in your link line to support the additional f90 runtime functions if your fortran code makes use of it.

The problem is caused by C++ mangling the real function names when it constructs code. By performing an "nm main.o" we can see what ld is really looking for:

halloc__Fv | 68|extern|entry |$CODE$
hallof__Fv | |undef |code |

As you can see, aCC has attached an "_Fv" denoting a (void) argument list. If you wish to use the functions as if they were C, you must 'extern "C"' them.

That is:

<< main.c >>


extern "C" void halloc(void);
extern "C" void hallof(void);

int main(unsigned int argc,char **argv)
/* c calls fortran: */
/* c calls c: */

void halloc(void){ printf("hallo cn"); }

$ f90 -c help.f
external subroutine HALLOF

6 Lines Compiled
$ aCC -c main.c
$ aCC -o test main.o help.o
$ ./test
hallo cnhallo cn$

For more about this, please see the "Mixing C++ with Other Languages" section of the aCC online programmers guide (run "aCC +help").