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Table 3-2 “HP C versus HP Fortran 90 Storage ” shows the differences
in storage allocation between HP C and HP Fortran 90. The notes
the table refers to are located after the table in the section called
"Notes on HP C and HP Fortran 90." Table 3-2 HP C versus HP Fortran 90 Storage HP C Type | HP C Description | HP Fortran 90 Type | HP Fortran 90 Description |
|---|
char,
signed char,
char enum | 1 byte, byte aligned |
| 1 byte, 1-byte aligned | unsigned char | 1 byte, byte aligned | CHARACTER*1 | 1 byte, 1-byte aligned | short,
short enum | 2 bytes, 2-byte aligned | INTEGER*2 | 2 bytes, 2-byte aligned | unsigned short | 2 bytes, 2-byte aligned |
|
| int,
int enum | 4 bytes, 4-byte aligned | INTEGER*4
or INTEGER | 4 bytes, 4-byte aligned | unsigned int | 4 bytes, 4-byte aligned |
|
| long,
long enum | 4 bytes, 4-byte aligned (8 bytes in LP64) | INTEGER*4
or INTEGER | 4 bytes, 4-byte aligned | unsigned long | 4 bytes, 4-byte aligned (8 bytes in LP64) |
|
| float | 4 bytes, 4-byte aligned | REAL
or REAL*4 | 4 bytes, 4-byte aligned | double | 8 bytes, 8-byte aligned | REAL*8
or DOUBLE PRECISION | 8 bytes, 8-byte aligned | long double | 16 bytes, 16-byte aligned | REAL*16 | 16 bytes, 16-byte aligned | (See Note 1) | 8 bytes, 4-byte aligned | COMPLEX
or COMPLEX*8 | 8 bytes, 4-byte aligned | (See Note 2) | 16 bytes, 8-byte aligned | DOUBLE COMPLEX
or COMPLEX*16 | 16 bytes, 8-byte aligned | enum | 4 bytes, 4-byte aligned | INTEGER*4
or INTEGER | 4 bytes, 4-byte aligned | pointer to type
long pointer to type |
| Not available |
| string (char *) |
| CHARACTER*n
(See Note 3) |
| char
array |
| CHARACTER*1
array (See Notes 4 &5) |
| (See Note 5) |
| Hollerith array |
| arrays | Size is number of elements times element
size. Aligned according to element type. | (See Note 4) | Size is number of elements times element
size. Aligned according to element type. | struct | (See Note 6) | STRUCTURE | Used to declare Fortran 90 record structures. | union | (See Note 6) | UNION | Used to declare Fortran 90 union types. | short
(used for logical test) | 2 bytes, 2-byte aligned | LOGICAL*2
(See Note 7) | 2 bytes, 2-byte aligned | int
(used for logical test) | 4 bytes, 4-byte aligned | LOGICAL*4
(See Note 7) | 4 bytes, 4-byte aligned | void |
| Used when calling a SUBROUTINE |
| function |
| Used when calling a FUNCTION |
|
Notes on HP C and HP Fortran 90 | |
The following HP C structure is equivalent to the HP Fortran
90 type listed in the table: struct complex {
float real_part;
float imag_part;
}; |
The following HP C structure is equivalent to the
HP Fortran 90 type listed in the table: struct double_complex {
double real_part;
double imag_part;
}; |
HP Fortran 90 passes strings as parameters using
string descriptors corresponding to the following HP C declarations: char *char_string; /* points to string */
int len; /* length of string */ |
HP C stores arrays in row-major order, whereas HP
Fortran 90 stores arrays in column-major order. The lower bound
for HP C is always zero; for HP Fortran 90, the default lower bound
is 1. HP C terminates character strings with a null byte,
while HP Fortran 90 does not. The size is equal to the size of all members plus
any padding needed for the alignment. (See Chapter 2 for details
on alignment.) The alignment is that of the member with the strictest
alignment requirement. HP C and HP Fortran 90 do not share a common definition
of true or false. In HP Fortran 90, logical values are determined
by the low-order bit of the high-order byte. If this bit is 1, the
logical value is .TRUE.,
and if the bit is zero, the logical value is .FALSE..
HP C interprets nonzero value as true and interprets
zero as false.
Mixing C and Fortran File I/O | |
A Fortran unit cannot be passed to a C routine to perform
I/O on the associated file. Nor can a C file pointer be
used by a Fortran routine. However, a file created by a program
written in either language can be used by a program of the other
language if the file is declared and opened within the latter program.
C accesses the file using I/O subroutines and intrinsics.
This method of file access can also be used from Fortran instead
of Fortran I/O. Be aware that HP Fortran 90 on HP 9000 workstations and servers
using HP-UX uses the unbuffered I/O system calls read
and write (described
in the HP-UX Reference manual) for all terminal
I/O, magnetic tape I/O, and direct access I/O.
It uses the system calls fread
and fwrite for
all other I/O. This can cause problems in programs that
mix C and Fortran I/O. In particular, C programs that use
stdio(3S) output
procedures such as printf
and fwrite and
Fortran output statements must flush stdio
buffers (by calling the libc
function fflush)
if they are in use before returning to Fortran output or the I/O
may be asynchronous (if the library is using write). Mixing Fortran direct, terminal, or tape READ statements with stdio fread
input results in the Fortran READ commencing from the beginning
of the next block after the contents of the buffer, not from the
current position of the input cursor in the fread
buffer. The same situation in reverse may occur by mixing read
with a Fortran sequential disc read. You can avoid these problems
by using only the read
and write calls
in the C program that the Fortran I/O library uses. Passing Parameters Between HP C and HP Fortran 90 | |
All parameters in HP Fortran 90 are passed by reference. This
means that all arguments in an HP C call to an HP Fortran 90 routine
must be pointers. In addition, all parameters in an HP C routine
called from HP Fortran 90 must be pointers, unless the HP Fortran
90 code uses the $ALIAS
directive to define the parameters as value parameters. Refer to
the example called "HP Fortran 90 Nested Structure" later in this
chapter. Passing string variables of any length must
be done by: building and passing a two-parameter descriptor (defined
in Note 3 above), initializing the string appropriately, and by
passing two arguments. The two arguments are the pointer
to the characters and the value of the length word. This is shown
below: char *chars = "Big Mitt";
int len;
.
.
.
len = strlen(chars);
pass_c_string (chars, len);
.
.
. |
Linking HP Fortran 90 Routines on HP-UX | |
When calling HP Fortran 90 routines on an HP-UX system, you
have to include the HP Fortran 90 run-time libraries by adding the
option: to the cc
command line. For details on linking external libraries, see the -l
option of the cc(1)
and ld(1) commands
in the HP-UX Reference manual. |
