Silicon Graphics IRIS Workstation, User Manual

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80 IRIS WORKSTATION GUIDE
Version 1.0
Appendix D:
int and will also be passed as a 32-bit value. Storing into any of these
parameters will not have any effect on the original FORTRAN data.
• A copy of the character string whose address is str1 would be
passed. C may store into this freely without affecting FORTRAN.
The character string will be null-terminated.
• A pointer to each of the character arrays str2 and str3 will be passed
to C. These character arrays will not be null-terminated, and storing
into them will affect the original FORTRAN data.
If this was a function passed to mkc2f , calling FORTRAN from C would cause
all of the parameters to be transformed to reference parameters but storing into
the parameters s , c , f , or d would not affect the original C variables. FORTRAN
would be passed one as the length of elements of the array str2 , and thirty as the
length of elements of the array str3 .
Lengths of FORTRAN Character Arrays
When FORTRAN is calling C, a character string 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 use of the standard C function strlen . If a character
variable is specified as a character array in the C parameter list, it may be
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 that need this information, the wrapper will pass it by extending the
C parameter list. For example, if the C function header is specified as:
func1(str1,i,cptr,j,str2)
char str1[],*cptr,str2[];
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 str1 , and the
seventh will be the length str2 . The C function func1() must index off of the
stack to retrieve these hidden parameters. In the case above, the length of strl as
passed by FORTRAN could be copied into str1_len by
char **s;
int str1_1en;
s = &(char *)str2; str1_1en = (int)(*(s+1))
Similarly, the length of the array str2 can be accessed by
(int)(*(s+2))