GNU Info

(g77-295.info)f2c Skeletons and Prototypes

---

Next: C++ Considerations Prev: C Access to Type Information Up: Interoperating with C and C++

---

Enter node , (file) or (file)node

Generating Skeletons and Prototypes with `f2c'
----------------------------------------------

   A simple and foolproof way to write `g77'-callable C routines--e.g.
to interface with an existing library--is to write a file (named, for
example, `fred.f') of dummy Fortran skeletons comprising just the
declaration of the routine(s) and dummy arguments plus `END' statements.
Then run `f2c' on file `fred.f' to produce `fred.c' into which you can
edit useful code, confident the calling sequence is correct, at least.
(There are some errors otherwise commonly made in generating C
interfaces with `f2c' conventions, such as not using `doublereal' as
the return type of a `REAL' `FUNCTION'.)

   `f2c' also can help with calling Fortran from C, using its `-P'
option to generate C prototypes appropriate for calling the Fortran.(1)
If the Fortran code containing any routines to be called from C is in
file `joe.f', use the command `f2c -P joe.f' to generate the file
`joe.P' containing prototype information.  `#include' this in the C
which has to call the Fortran routines to make sure you get it right.

   Note: Arrays (DIMENSION), for information on the differences
between the way Fortran (including compilers like `g77') and C handle
arrays.

   ---------- Footnotes ----------

   (1) The files generated like this can also be used for inter-unit
consistency checking of dummy and actual arguments, although the
`ftnchek' tool from `ftp://ftp.netlib.org/fortran' or
`ftp://ftp.dsm.fordham.edu' is probably better for this purpose.