fortc - Online in the Cloud

PROGRAM:

NAME

fortc - Unidata utility to generate fortran-compatible C code

SYNOPSIS

fortc [-L LibDir] [-O OpSys] file

DESCRIPTION

fortc Reads C code from `file', transforms it into FORTRAN compatible code, and then
writes the result to standard output. The transformation is operating-system dependent
because there are no standards in this matter.

The target operating-system can be specified in several ways. If the `-O' option is
given, then the operating-system specified by its argument is used; otherwise, if the
environmental variable `OS' exists, then the operating-system specified by it's value is
used; otherwise, the default operating-system -- determined at installation time -- is
used.

Global names that are not function definitions but that are to be accessible from both C
and FORTRAN should be enclosed by the `FC_NAME()' macro:

extern int FC_NAME(foo)(void); /* FORTRAN function */

extern struct {
float f;
int i;
} FC_NAME(comblk); /* FORTRAN common block */

cfoo()
{
return FC_NAME(foo)(); /* call FORTRAN function */
}

C functions which are to be called from FORTRAN are written as follows:

int
/*FORTRAN*/
foo(
character pathname, /* file name of new file */
real amount, /* amount to frobdicate by */
doubleprecision dbl, /* amount to tizzle by */
void function errf, /* error routine */
integer rcode /* returned error code */)
{
...

or, equivalently,

int
/*FORTRAN*/
foo(char* pathname, float* amount, double* dbl,
void (*errf)(), int* rcode)
{
...

The points to note in writing FORTRAN-compatible functions are:

1. Functions to be transformed are marked by a proceeding `/*FORTRAN*/' comment, which
must appear on the line prior to the function name. Any return-type declarations must
proceed the comment.

2. The formal parameters must be declared within function parentheses and be separated by
commas.

3. The formal parameters are restricted to the following types:

character or char*
For Fortran character-variables.

doubleprecision or double*"
For double-precision floating-point values.

real or float*
For single-precision floating-point values.

integer or int*
For integer values.

type function name or type (*name)()
For functions returning type `type'.

4. There must be nothing important after the opening brace, `{', and on the same line.

The functions should be written using variables with the same names as the formal
parameters, and with the same semantics. In the case of formal parameters of type
`character' (i.e. Fortran character-variables), a variable with the same name will exist
and will be of type `char*'. In addition, for each character-variable argument, a local
variable of integral type will be created and its value will be the size of the associated
character-variable. The name of this variable will be the name of the associated
character variable with "_len" appended (e.g. "pathname_len"). These length variables may
be used in the function just like any other variable.

For example, under SunOS the previous function would become (if it is contained in the
file `foo.src'):

#line 1 "foo.src"
unsigned int
#line 2 "foo.src"
foo_(pathname, amount, errf, rcode, pathname_len)
char *pathname;
int pathname_len;
float *amount;
void (*errf)();
int *rcode;
{
#line 9 "foo.src"

Note that 1) preprocessor line directives have been added; 2) the function name has been
suffixed with an underscore; and 3) a formal parameter, `pathname_len', has been created.

Under UNICOS, the same file would become

#include <fortran.h>
#line 1 "foo.src"
unsigned int
#line 2 "foo.src"
FOO(pathnamed, amount, errf, rcode)
_fcd pathnamed;
float *amount;
void (*errf)();
int *rcode;
{
char *pathname = _fcdtocp (pathnamed);
unsigned pathname_len = _fcdlen (pathnamed);
#line 9 "foo.src"

Note, in particular, the additional `#include <fortran.h>' and the creation and
initialization of the local variables `pathname' and `pathname_len'.

This utility is implemented as a script and uses the system-supplied utilities sed(1) and
m4(1).

OPTIONS

-L LibDir"
Defines the directory containing the `fortc' library files. The default is
determined at installation time.

-O OpSys
Defines the operating-system as OpSys. Known values include `aix', `convexos',
`domainos', `hpux', `irix', `msoft', `next-absoft', `newsos', `sunos', `ultrix',
`unicos', and `vms'. To allow for greater flexibility, the known values may have
any suffix (e.g. `sunos_4.1').

ENVIRONMENT

OS Defines the operating system if the `-O' option is not specified. Known values
are the same as the -O option.

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