Technical data

Chapter 3: Fortran Program Interfaces

• S, C, and D would be passed as values of length 16 bits, 64 bits, and 8

bits, respectively. F would be converted to a 64-bit DOUBLE before

being passed, unless the –f option had been speciﬁed. If the –f option

had been speciﬁed, F would be passed as a 32-bit value. Because the

type of I is not speciﬁed, it would be assumed to be INT and would

also be passed as a 32-bit value. Storing values in any of these

parameters would not have any effect on the original Fortran data.

Fortran Character Array Lengths

When the wrapper generator is used, a character variable that is speciﬁed as

char* in the C parameter list is copied and null terminated. C may thus

determine the length of the string by the use of the standard C function

strlen.

If a character variable is speciﬁed as a character array in the C parameter list,

the address of the character variable is passed, making it impossible for C to

determine its length, as it is not null terminated. When the call occurs, the

wrapper code receives this length from Fortran. For those C functions

needing this information, the wrapper passes it by extending the C

parameter list.

For example, if the C function header is speciﬁed as follows

func1 (carr1,i,str,j,carr2)

char carr1[],*str,carr2[];

int i, j;

{}

mkf2c will pass a total of seven parameters to C. The sixth parameter will be

the length of the Fortran character variable corresponding to carr1, and the

seventh will be the length of carr2. The C function func1() must use the

varargs macros to retrieve these hidden parameters. mkf2c will ignore the