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<HTML>
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<TITLE>Using Project Files</TITLE>
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<A HREF="toc.html">Table of Contents</A><P>
<P>Previous: <A HREF="sect5.html">Changing the Defaults</A><HR><P>
<H2><A NAME="sect6" HREF="toc.html#toc6">Using Project Files </A></H2>
This section contains detailed information on how to use project
files most effectively, and how to avoid some pitfalls. <P>
One can divide
the checks <B>ftnchek </B> does into two categories, local and global. Local
checking is restricted to within a single routine, and catches things
like uninitialized variables, unintended loss of precision in arithmetic
expressions, etc. This sort of checking can be done on each subprogram
independently. Furthermore, local checking of a subprogram does not need
to be repeated when some other subprogram is changed. Global checking
catches things like calling a subroutine with the wrong argument types,
or disagreeing in common block declarations. It requires looking at the
whole set of subprograms interacting with each other. <P>
The purpose of project
files is to allow the local checking and global checking steps to be separated.
Assuming that each subprogram is in its own source file, you can run
<B>ftnchek </B> once on each one to do local checking while suppressing global
checking. Then <B>ftnchek </B> can be run once on all the project files together
to do the global checking. The sample makefile below shows how to automate
this task. The ``.f.prj '' target updates a project file for a particular file
any time the source file changes. The information needed for global checking
is saved in the project file. The ``check '' target does the combined global
checking. Typically ``make check '' would repeat the ``ftnchek <A HREF="project.html">-project</A> '' step
only on changed source files, then do the global check. This is obviously
a big advantage for large programs, when many subprograms seldom if ever
change. <P>
It is best when using project files to place each subprogram in
a separate source file. If each source file may contain more than one
subprogram, it complicates the definition of ``local'' and ``global'' checking
because there is some inter-module checking that is contained within a
file. <B>ftnchek </B> tries to do the right thing in this case, but there are
some complications (described below) due to the trade-off between avoiding
re-doing cross-checks and preserving information about the program's structure.
<P>
Ordinarily, to do the least amount of re-checking, project files should
be created with the <B><A HREF="library.html">-library</A> </B> flag in effect. In this mode, the information
saved in the project file consists of all subprogram declarations, all
subprogram invocations not resolved by declarations in the same file,
and one instance of each COMMON block declaration. This is the minimum
amount of information needed to check agreement between files. <P>
If the source
file contains more than one routine, there are some possible problems
that can arise from creating the project file in library mode, because
the calling hierarchy among routines defined within the file is lost.
Also, if the routines in the file make use of COMMON blocks that are shared
with routines in other files, there will not be enough information saved
for the correct checking of set and used status of COMMON blocks and COMMON
variables according to the <B><A HREF="usage.html">-usage</A> </B> setting. Therefore if you plan to use
project files when <B><A HREF="usage.html">-usage</A> </B> checking is turned on (which is the default
situation), and if multiple routines in one project file share COMMON
blocks with routines in other files, the project files should be created
with the <B><A HREF="library.html">-library</A> </B> flag turned off. In this mode, <B>ftnchek </B> saves, besides
the information listed above, one invocation of each subprogram by any
other subprogram in the same file, and all COMMON block declarations.
This means that the project file will be larger than necessary, and that
when it is read in, <B>ftnchek </B> may repeat some inter-module checks that it
already did when the project file was created. If each project file contains
only one module, there is no loss of information in creating the project
files in library mode. <P>
Because of the possible loss of information entailed
by creating a project file with the <B><A HREF="library.html">-library</A> </B> flag in effect, whenever
that project file is read in later, it will be treated as a library file
regardless of the current setting of the <B><A HREF="library.html">-library</A> </B> flag. On the other hand,
a project file created with library mode turned off can be read in later
in either mode. <P>
Here is an example of how to use the UNIX <B>make </B> utility
to automatically create a new project file each time the corresponding
source file is altered, and to check the set of files for consistency.
Add these lines to your makefile . The example assumes that a macro OBJS
has been defined which lists all the names of object files to be linked
together to form the complete executable program. (In this makefile , the
indented lines should each begin with a tab, not blanks.) If any source
file contains multiple routines that share common blocks among themselves,
then the no-com-\* option should be removed from NOGLOBAL , and/or drop
the <A HREF="library.html">-library</A> flag. <BR>
<PRE>
# tell make what a project file suffix is
.SUFFIXES: .prj
# these options suppress global checks.
NOGLOBAL=<A HREF="usage.html">-usage</A>=no-ext-undefined,no-com-\*
# tell make how to create a .prj file from a .f file
.f.prj:
ftnchek <A HREF="project.html">-project</A> $(NOGLOBAL) <A HREF="library.html">-library</A> $<
# set up macro PRJS containing project filenames
PRJS= $(OBJS:.o=.prj)
# "make check" will check everything that has been changed.
check: $(PRJS)
ftnchek $(PRJS)
</PRE>
<P><HR><P>Next: <A HREF="sect7.html">an Example </A>
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