HP OpenVMS Systems Documentation

HP Fortran for OpenVMS
User Manual

Example 1-1 shows a short Fortran 90/95 main program using free-form source.

! File hello.f90

     PROGRAM HELLO_TEST

       PRINT *, 'hello world'
       PRINT *, ' '

     END PROGRAM HELLO_TEST

To create and revise your source files, use a text editor, such as the Extensible Versatile Editor (EVE). For instance, to use EVE to edit the file HELLO.F90, enter:

$ EDIT HELLO.F90

The following FORTRAN command compiles the program named HELLO.F90. The LINK command links the compiled object file into an executable program file named HELLO.EXE:

$ FORTRAN HELLO.F90
$ LINK HELLO

In this example, because all external routines used by this program reside in standard OpenVMS libraries searched by the LINK command, additional libraries or object files are not specified on the LINK command line.

To run the program, enter the RUN command and the program name:

$ RUN HELLO

If the executable program is not in your current default directory, specify the directory before the file name. Similarly, if the executable program resides on a different device than your current default device, specify the device name and directory name before the file name.

For More Information:

• On the OpenVMS programming environment, see the operating system documents listed in the Preface of this manual.
• On specifying files on an OpenVMS system, see the OpenVMS User's Manual.

Example 1-2 shows a sample HP Fortran main program using free-form source that uses a module and an external subprogram.

The function CALC_AVERAGE is contained in a separately created file and depends on the module ARRAY_CALCULATOR for its interface block.

 ! File: main.f90
 ! This program calculates the average of five numbers

   PROGRAM MAIN

     USE ARRAY_CALCULATOR                 (1)
     REAL, DIMENSION(5) :: A = 0
     REAL :: AVERAGE

     PRINT *, 'Type five numbers: '
     READ  (*,'(BN,F10.3)') A
     AVERAGE = CALC_AVERAGE(A)            (2)
     PRINT *, 'Average of the five numbers is: ', AVERAGE

   END PROGRAM MAIN

1. The USE statement accesses the module ARRAY_CALCULATOR. This module contains the function declaration for CALC_AVERAGE (use association).
2. The 5-element array is passed to the function CALC_AVERAGE, which returns the value to the variable AVERAGE for printing.

Example 1-3 shows the module referenced by the main program. This example program shows more Fortran 90 features, including an interface block and an assumed-shape array.

 ! File: array_calc.f90.
 ! Module containing various calculations on arrays.

   MODULE ARRAY_CALCULATOR
     INTERFACE
       FUNCTION CALC_AVERAGE(D)
         REAL :: CALC_AVERAGE
         REAL, INTENT(IN) :: D(:)
       END FUNCTION CALC_AVERAGE
     END INTERFACE

   ! Other subprogram interfaces...

   END MODULE ARRAY_CALCULATOR

Example 1-4 shows the function declaration CALC_AVERAGE referenced by the main program.

 ! File: calc_aver.f90.
 ! External function returning average of array.

   FUNCTION CALC_AVERAGE(D)
     REAL :: CALC_AVERAGE
     REAL, INTENT(IN) :: D(:)
     CALC_AVERAGE = SUM(D) / UBOUND(D, DIM = 1)
   END FUNCTION CALC_AVERAGE

During the early stages of program development, the three files might be compiled separately and then linked together, using the following commands:

$ FORTRAN ARRAY_CALC.F90
$ FORTRAN CALC_AVER.F90
$ FORTRAN MAIN.F90
$ LINK/EXECUTABLE=CALC.EXE MAIN, ARRAY_CALC, CALC_AVER

In this sequence of FORTRAN commands:

• Each of the FORTRAN commands creates one object file (OBJ file type).
• The first FORTRAN command creates the object file ARRAY_CALC.OBJ and the module file ARRAY_CALCULATOR.F90$MOD. The name in the MODULE statement (ARRAY_CALCULATOR) in Example 1-3 determines the file name of the module file. The FORTRAN command creates module files in the process default device and directory with a F90$MOD file type.
• The second FORTRAN command creates the file CALC_AVER.OBJ (Example 1-4).
• The third FORTRAN command creates the file MAIN.OBJ (Example 1-2) and uses the module file ARRAY_CALCULATOR.F90$MOD.
• The LINK command links all object files (OBJ file type) into the executable program named CALC.EXE.

To allow more optimizations to occur (such as the inline expansion of called subprograms), compile the entire set of three source files together using a single FORTRAN command:

$ FORTRAN/OBJECT=CALC.OBJ ARRAY_CALC.F90 + CALC_AVER.F90 + MAIN.F90

The order in which the file names are specified is significant. This FORTRAN command:

• Compiles the file ARRAY_CALC.F90, which contains the module definition (shown in Example 1-3), and creates its object file and the file ARRAY_CALCULATOR.F90$MOD in the process default device and directory.
• Compiles the file CALC_AVER.F90, which contains the external function CALC_AVERAGE (shown in Example 1-4).
• Compiles the file MAIN.F90 (shown in Example 1-2). The USE statement references the module file ARRAY_CALCULATOR.F90$MOD.
• Creates a single object file named CALC.OBJ.

When you omit the file type on the FORTRAN command line, the FORTRAN command searches for a file with the F90 file type before a file with the FOR or F file type, so you can enter the previous command (without file types) as follows:

$ FORTRAN/OBJECT=CALC.OBJ ARRAY_CALC + CALC_AVER + MAIN

Use a LINK command to link the single object file into an executable program:

$ LINK CALC

When you omit the file type on the LINK command line, the Linker searches for a file with a file type of OBJ. Unless you will specify a library on the LINK command line, you can omit the OBJ file type.

1.4.2 Running the Sample Program

If the current default directory contains the file named CALC you can run the program by entering the RUN command followed by its name:

$ RUN CALC

When you omit the file type on the RUN command line, the image activator searches for a file with a file type of EXE (you can omit the EXE file type).

When running the sample program, the PRINT and READ statements in the main program result in the following dialogue between user and program:

Type five numbers:
55.5
4.5
3.9
9.0
5.6
Average of the five numbers is:   15.70000

To debug a program using the OpenVMS Debugger, compile and link with the /DEBUG qualifier to request additional symbol table information for source line debugging in the object and executable program files. The following FORTRAN command names the object file CALC_DEBUG.OBJ. The LINK command then creates the program file CALC_DEBUG.EXE with full debugging information:

$ FORTRAN/DEBUG/OBJECT=CALC_DEBUG.OBJ/NOOPTIMIZE ARRAY_CALC + CALC_AVER + MAIN
$ LINK/DEBUG CALC_DEBUG

The OpenVMS debugger has a character-cell interface and a windowing interface (available with the DECwindows Motif product). To debug an executable program named CALC_DEBUG.EXE, enter the following command:

$ RUN CALC_DEBUG

For more information on running the program within the debugger and the windowing interface, see Chapter 4.

1.5 Program Development Stages and Tools

This manual primarily addresses the program development activities associated with implementation and testing phases. For information about topics usually considered during application design, specification, and maintenance, see your operating system documentation or appropriate commercially published documentation.

HP Fortran provides the standard features of a compiler and the OpenVMS operating system provides a linker.

Use a LINK command to link the object file into an executable program.

Table 1-1 describes some of the software tools you can use when developing (implementing) and testing a program:

To perform other program development functions at various stages of program development, use the following DCL commands:

• Use the LIBRARIAN command to create an object or text library, add or delete library modules in a library, list the library modules in a library, and perform other functions. For more information, enter HELP LIBRARIAN or see the VMS Librarian Utility Manual.
• Use the LINK/NODEBUG command to remove symbolic and other debugging information to minimize image size. For more information, see Chapter 3.
• The LINK/MAP command creates a link map, which shows information about the program sections, symbols, image section, and other information.
• The ANALYZE/OBJECT command shows which compiler compiled the object file and the version number used. It also does a partial error analysis and shows other information.
• The ANALYZE/IMAGE command checks information about an executable program file. It also shows the date it was linked and the version of the operating system used to link it.

For More Information:

• On the OpenVMS programming environment, see the Preface of this manual.
• On DCL commands, use DCL HELP or see the HP OpenVMS DCL Dictionary.

This chapter describes:

• Section 2.1, Functions of the Compiler
• Section 2.2, FORTRAN Command Syntax, Use, and Examples
• Section 2.3, FORTRAN Command Qualifiers
• Section 2.4, Creating and Maintaining Text Libraries
• Section 2.5, Using CDD/Repository
• Section 2.6, Compiler Limits, Diagnostic Messages, and Error Conditions
• Section 2.7, Compiler Output Listing Format

The primary functions of the HP Fortran compiler are to:

• Verify the HP Fortran source statements and to issue messages if the source statements contain any errors
• Venerate machine language instructions from the source statements of the HP Fortran program
• Group these instructions into an object module for the OpenVMS Linker

When the compiler creates an object file, it provides the linker with the following information:

• The program unit name. The program unit name is the name specified in the PROGRAM, MODULE, SUBROUTINE, FUNCTION, or BLOCK DATA statement in the source program. If a program unit does not contain any of these statements, the source file name is used with $MAIN (or $DATA, for block data subprograms) appended.
• A list of all entry points and common block names that are declared in the program unit. The linker uses this information when it binds two or more program units together and must resolve references to the same names in the program units.
• Traceback information, used by the system default condition handler when an error occurs that is not handled by the program itself. The traceback information permits the default handler to display a list of the active program units in the order of activation, which aids program debugging.
• A symbol table, if specifically requested (/DEBUG qualifier). A symbol table lists the names of all external and internal variables within a object module, with definitions of their locations. The table is of primary use in program debugging.

For More Information:

On the OpenVMS Linker, see Chapter 3.

2.2 FORTRAN Command Syntax, Use, and Examples

The FORTRAN command initiates compilation of a source program.

The command has the following form:

/qualifiers

Indicates either special actions to be performed by the compiler or special properties of input or output files.

file-spec-list

Specifies the source files containing the program units to be compiled. You can specify more than one source file:

• If source file specifications are separated by commas (,), the programs are compiled separately.
• If source file specifications are separated by plus signs (+), the files are concatenated and compiled as one program.

When compiling source files with the default optimization (or additional optimizations), concatenating source files allows full interprocedure optimizations to occur.

In interactive mode, you can also enter the file specification on a separate line by entering the command FORTRAN, followed by a carriage return. The system responds with the following prompt:

 _File:

Enter the file specification immediately after the prompt and then press Return.

2.2.1 Specifying Input Files and Source Form

If you omit the file type on the FORTRAN command line, the compiler searches first for a file with a file type of F90. If a file with a file type of F90 is not found, it then searches for file with a file type of FOR and then F.

For example, the following FORTRAN command line shows how file type searching occurs:

$ FORTRAN PROJ_ABC

This FORTRAN command searches for the following files:

1. It searches first for PROJ_ABC.F90.
2. If PROJ_ABC.F90 does not exist, it then searches for PROJ_ABC.FOR.
3. If PROJ_ABC.F90 and PROJ_ABC.FOR do not exist, it then searches for PROJ_ABC.F.

Indicate the Fortran 90 source form used in your source files by using certain file types or a command-line qualifier:

• For files using fixed form, use a file type of FOR or F.
• For files using free form, use a file type of F90.
• You can also specify the /SOURCE_FORM qualifier on the FORTRAN command line to specify the source form (FIXED or FREE) for:
  • All files on that command line (when used as a command qualifier)
  • Individual source files in a comma-separated list of files (when used as a positional qualifier)

For example, if you specify a file as PROJ_BL1.F90 on an FORTRAN command line (and omit the /SOURCE_FORM=FIXED qualifier), the FORTRAN command assumes the file PROJ_BL1.F90 contains free-form source code.

2.2.2 Specifying Multiple Input Files

When you specify a list of input files on the FORTRAN command line, you can use abbreviated file specifications for those files that share common device names, directory names, or file names.

The system applies temporary file specification defaults to those files with incomplete specifications. The defaults applied to an incomplete file specification are based on the previous device name, directory name, or file name encountered in the list.

The following FORTRAN command line shows how temporary defaults are applied to a list of file specifications:

$ FORTRAN USR1:[ADAMS]T1,T2,[JACKSON]SUMMARY,USR3:[FINAL]

The preceding FORTRAN command compiles the following files:

USR1:[ADAMS]T1.F90 (or .FOR or .F)
USR1:[ADAMS]T2.F90 (or .FOR  or .F)
USR1:[JACKSON]SUMMARY.F90 (or .FOR or .F)
USR3:[FINAL]SUMMARY.F90 (or .FOR or .F)

To override a temporary default with your current default directory, specify the directory as a null value. For example:

$ FORTRAN [OMEGA]T1, []T2

The empty brackets indicate that the compiler is to use your current default directory to locate T2.

FORTRAN qualifiers typically apply to the entire FORTRAN command line. One exception is the /LIBRARY qualifier, which specifies that the file specification it follows is a text library (positional qualifier). The /LIBRARY qualifier is discussed in Section 2.3.27.

You can specify multiple files on the FORTRAN command line. You can separate the multiple source file specifications with:

• Plus signs (+)
  All files separated by plus signs are concatenated and compiled as one program into a single object file.
  A positional qualifier after one of the file specifications applies to all files concatenated by plus signs (+). One exception is the /LIBRARY qualifier (used only as a positional qualifier).
  Concatenating source files allows full interprocedure optimizations to occur across the multiple source files (unless you specify certain command qualifiers, such as /NOOPTIMIZE and /SEPARATE_COMPILATION).
• Commas (,)
  When separated by commas, the files are compiled separately into multiple object files.
  A positional qualifier applies only to the file specification it immediately follows.
  Separate compilation by using comma-separated files (or by using multiple FORTRAN commands) prevents certain interprocedure optimizations.

If you use multiple FORTRAN commands to compile multiple HP Fortran source files that are linked together into the same program, you must be consistent when specifying any qualifiers that affect run-time results. For example, suppose you do the following:

1. Specify /FLOAT=IEEE_FLOAT on one command line
2. Specify /FLOAT=G_FLOAT on another command line
3. Link the resulting object files together into a program

When you run the program, the values returned for floating-point numbers in a COMMON block will be unpredictable. For qualifiers related only to compile-time behavior (such as /LIST and /SHOW), this restriction does not apply.