|Fortran Programming Guide|
This chapter briefly introduces two powerful program development tools,
makeand SCCS, that can be used very successfully with Fortran programs.
A number of good, commercially published books on using
makeand SCCS are currently available, including Managing Projects with make, by Andrew Oram and Steve Talbott, and Applying RCS and SCCS, by Don Bolinger and Tan Bronson. Both are from O'Reilly & Associates.
Facilitating Program Builds With the
makeutility applies intelligence to the task of program compilation and linking. Typically, a large application consists of a set of source files and
INCLUDEfiles, requiring linking with a number of libraries. Modifying any one or more of the source files requires recompilation of that part of the program and relinking. You can automate this process by specifying the interdependencies between files that make up the application along with the commands needed to recompile and relink each piece. With these specifications in a file of directives,
makeensures that only the files that need recompiling are recompiled and that relinking uses the options and libraries you need to build the executable. The following discussion provides a simple example of how to use
make. For a summary, see
A file called
makein a structured manner which source and object files depend on other files. It also defines the commands required to compile and link the files.
commonblock, and you wish to compile each
.ffile and link the three relocatable files, along with a series of libraries, into a program called
The makefile looks like this:
cat makefilepattern: pattern.o computepts.o startupcore.o
f77pattern.o computepts.o startupcore.o -lcore77 \-lcore -lsunwindow -lpixrect -o patternpattern.o: pattern.f commonblock
f77-c -u pattern.fcomputepts.o: computepts.f commonblock
f77-c -u computepts.fstartupcore.o: startupcore.f
f77-c -u startupcore.fdemo%
The first line of
makefileindicates that making
startupcore.o. The next line and its continuations give the command for making
patternfrom the relocatable
.ofiles and libraries.
Each entry in
makefileis a rule expressing a target object's dependencies and the commands needed to make that object. The structure of a rule is:
- Dependencies. Each entry starts with a line that names the target file, followed by all the files the target depends on.
- Commands. Each entry has one or more subsequent lines that specify the Bourne shell commands that will build the target file for this entry. Each of these command lines must be indented by a tab character.
makeutility looks for a file named
Makefilein the current directory and takes its instructions from that file.
makefileto determine all the target files it must process, the files they depend on, and the commands needed to build them.
- Finds the date and time each file was last changed.
- Rebuilds any target file that is older than any of the files it depends on, using the commands from
makefilefor that target.
makeutility's macro facility allows simple, parameterless string substitutions. For example, the list of relocatable files that make up the target program
patterncan be expressed as a single macro string, making it easier to change.
A macro string definition has the form:
NAME = string
Use of a macro string is indicated by:
which is replaced by
makewith the actual value of the macro string.
Now the macro can be used in both the list of dependencies as well as on the
f77link command for target
f77$(OBJ) -lcore77 -lcore -lsunwindow \-lpixrect -o pattern
For macro strings with single-letter names, the parentheses may be omitted.
Overriding of Macro Values
The initial values of
makemacros can be overridden with command-line options to
make. For example:
FFLAGS=-uOBJ = pattern.o computepts.o startupcore.opattern: $(OBJ)
f77$(FFLAGS) $(OBJ) -lcore77 -lcore -lsunwindow \-lpixrect -o patternpattern.o: pattern.f commonblockf77 $(FFLAGS) -c pattern.fcomputepts.o:
f77$(FFLAGS) -c computepts.f
Here, the definition of the
FFLAGSmacro on the
makecommand line overrides the
makefileinitialization, and both the
-Oflag and the
-uflag are passed to
f77. Note that
"FFLAGS="can also be used on the command to reset the macro to a null string so that it has no effect.
Suffix Rules in
To make writing a makefile easier,
makewill use its own default rules depending on the suffix of a target file. Recognizing the
f77compiler, passing as arguments any flags specified by the
-cflag, and the name of the source file to be compiled.
The example below demonstrates this rule twice:
OBJ = pattern.o computepts.o startupcore.oFFLAGS=-upattern: $(OBJ)
f77$(OBJ) -lcore77 -lcore -lsunwindow \-lpixrect -o patternpattern.o: pattern.f commonblock
f77$(FFLAGS) -c pattern.fcomputepts.o: computepts.f commonblockstartupcore.o: startupcore.f
makeuses default rules to compile
Similarly, suffix rules for
.f90files will also invoke the
f95compiler. However, there are no suffix rules currently defined for
.f95Fortran 95 source files or
.modFortran 95 module files.
Version Tracking and Control With SCCS
SCCS stands for Source Code Control System. SCCS provides a way to:
- Keep track of the evolution of a source file--its change history
- Prevent a source file from being simultaneously changed by other developers
- Keep track of the version number by providing version stamps
The basic three operations of SCCS are:
This section shows you how to use SCCS to perform these tasks, using the previous program as an example. Only basic SCCS is described and only three SCCS commands are introduced:
Controlling Files With SCCS
Putting files under SCCS control involves:
- Making the SCCS directory
- Inserting SCCS ID keywords into the files (this is optional)
- Creating the SCCS files
Making the SCCS Directory
SCCSmust be in uppercase.
Inserting SCCS ID Keywords
Some developers put one or more SCCS ID keywords into each file, but that is optional. These keywords are later identified with a version number each time the files are checked in with an SCCS
delgetcommand. There are three likely places to put these strings:
The advantage of using keywords is that the version information appears in the source listing and compiled object program. If preceded by the string @(#), the keywords in the object file can be printed using the
Included header files that contain only parameter and data definition statements do not generate any initialized data, so the keywords for those files usually are put in comments or in parameter statements. In some files, like ASCII data files or makefiles, the SCCS information will appear in comments.
SCCS keywords appear in the form
%and are expanded into their values by the SCCS
getcommand. The most commonly used keywords are:
%Z%expands to the identifier string
@(#)recognized by the
%M%expands to the name of the source file.
%I%expands to the version number of this SCCS maintained file.
%E%expands to the current date.
When this file is processed by SCCS, compiled, and the object file processed by the SCCS
whatcommand, the following is displayed:
f77 -c pattern.f...demo%
what patternpattern:pattern.f 1.2 96/06/10
Note Use of single letter derived type component names in Fortran 95 source code files can conflict with SCCS keyword recognition. For example, the Fortran 95 structure component reference
XZwhen passed through SCCS will become
XZafter an SCCS
get. Care should be taken not to define structure components with single letters when using SCCS on Fortran 95 programs. For example, had the structure reference in the Fortran 95 program been to
%YY%would not have been interpreted by SCCS as a keyword reference. Alternatively, the SCCS
get -koption will retrieve the file without expanding SCCS keyword IDs.
Creating SCCS Files
Checking Files Out and In
Once your source code is under SCCS control, you use SCCS for two main tasks: to check out a file so that you can edit it, and to check in a file you have finished editing.
SCCS then makes a writable copy of
computepts.fin the current directory, and records your login name. Other users cannot check the file out while you have it checked out, but they can find out who has checked it out.
This command causes the SCCS system to:
- Make sure that you are the user who checked out the file by comparing login names
- Prompt for a comment from you on the changes
- Make a record of what was changed in this editing session
- Delete the writable copy of
computepts.ffrom the current directory
- Replace it by a read-only copy with the SCCS keywords expanded
delgetcommand is a composite of two simpler SCCS commands,
deltacommand performs the first three tasks in the list above; the
getcommand performs the last two tasks.
Sun Microsystems, Inc.
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