HP Fortran Programmer's Guide (B3908-90031; September 2011)

Compiling and linking
Special-purpose compilations
Chapter 2 85
Special-purpose compilations
The default behavior of the HP Fortran compiler has been designed to handle typical compilations. Most
applications should require no more than a few of the f90 options to compile successfully (see Table on
page 25 for a list of commonly used options).
However, the compiler can also meet the needs of more specialized compilations. This section explains how
to use the f90 command for the following purposes:
• To compile programs that contain Fortran modules.
• To compile programs that will execute on different PA-RISC machines.
• To create object files for shared libraries.
• To process source files that contain C preprocessor directives.
• To create demand-loadable programs.
• To create shareable executable programs.
• To compile 32-bit programs in 64-bit mode.
Compiling programs with modules
One of the features of standard Fortran is the module, a program unit that facilitates shared access to data
and procedures. Modules are fully described in the HP Fortran Programmer’s Reference.
A benefit to using modules is that they provide interface information to the compiler, allowing it to catch
mismatch errors between (for example) dummy arguments and actual arguments. When the
HP Fortran compiler processes a file that defines a module, it generates a .mod file with the interface
information. Later, when the compiler processes a file that uses the module, it reads the .mod file and checks
that module entities that are referenced in the using file correctly match the information in the .mod file.
To make the .mod files available to the compiler, you must therefore compile the files that define modules
before the files that use modules. Likewise, if you make changes to a file that defines a module, you must
recompile that file as well as any files that use the module, in that order.
Also, if a module is defined and used in the same file, the definition must lexically precede any USE
statements that reference the module. This requirement allows the compiler to generate the .mod file first, so
that it can resolve the references in any USE statements.
This section discusses the following topics:
• How to compile a program that uses modules
• How to design makefiles to work with modules