WHOUSES

- NAME
- MOTTO
- SYNOPSIS
- DESCRIPTION
- .AUDIT FILES
- CLASSIC CODE ANALYSIS COMPARED

- MINUSES
- PLUSES

- AUTHOR
- COPYRIGHT
- STATUS
- PORTING
- SEE ALSO

# NAME

whouses - impact analysis in a clearmake build environment

# MOTTO

You give me a clean CR, I'll give you a clean impact analysis.

# SYNOPSIS

Run this script with the `-help` option for usage details. Here are some additional sample usages with explanations:

      whouses foobar.h

Shows all DO's that make use of any file matching /foobar.h/.

      whouses -recurse foobar.h

Same as above but follows the chain of derived files recursively.

      whouses -exact /vobs_xyz/include/foobar.h

Shows all DO's that make use of the specified file (must be given as a an absolute pathname).

# DESCRIPTION

Whouses provides a limited form of ``impact analysis'' in a clearmake build environment. This is different from traditional impact analysis (see CLASSIC CODE ANALYSIS COMPARED below for details) and in particular operates at the granularity of files rather than language elements.

Whouses is best described by example. Imagine you have a VOB '/vobs_sw' in which you build the incredibly simple application foo from foo.c. You have a Makefile which compiles foo.c to foo.o and then links it to produce foo. And let's further assume you've just done a build using clearmake.

Now, foo is a DO which has a config record (``CR'') showing how it was made. Whouses analyzes that CR and prints the data in easy-to-read indented format. For instance:

            % whouses -cr foo foo.c
            /vobs_sw/src/foo.c  =>
              /vobs_sw/src/foo.o

The ``-cr foo'' points to the derived object from which to extract and analyze the CR; it will be implicit in the remaining examples. The output indicates that foo.o uses foo.c, or in other words that foo.c is a contributor to foo.o. If we add the -recurse flag:

            % whouses -r foo.c
            /vobs_sw/src/foo.c =>
              /vobs_sw/src/foo.o
                /vobs_sw/src/foo

We see all files to which foo.c contributes, indented according to how many generations removed they are. If we now add -terminals

            % whouses -r -t foo.c
            /vobs_sw/src/foo.c =>
              /vobs_sw/src/foo

Intermediate targets such as foo.o are suppressed so we see only the ``final'' targets descended from foo.c.

We can also go in the other direction using -backwards:

            % whouses -b -e foo
            /vobs_sw/src/foo <=
              /vobs_sw/src/foo.o

Which shows foo.o as a progenitor of foo. Note that the arrow (<=) is turned around to indicate -backwards mode. We also introduced the -exact flag here. By default arguments to whouses are treated as patterns, not file names, and since foo has no extension it would have matched foo.c and foo.o as well. We can combine recursion with backwards mode:

            % whouses -b -e -r foo
            /vobs_sw/src/foo <=
              /vobs_sw/src/foo.o
                  /vobs_sw/src/foo.c
                  /vobs_sw/src/foo.h
                  /vobs_sw/src/bar.h

And discover that foo.h and bar.h were also used.

When used recursively in the forward direction, this script answers the question ``if I change file X, which derived files will need to be rebuilt''? This is the classic use, the one for which it was written.

Because extracting a recursive CR can be quite slow, whouses provides ways of dumping the CR data to a file representation for speed. Use of -save:

            % whouses -cr foo -save ...

will write out the data to foo.crdb. Subsequently, if foo.crdb exists and is newer than foo data will be taken from it rather than re-generating the recursive catcr report. See also the -db and -fmt flags.

The default save format is that of Data::Dumper. It was chosen because it results in a nicely indented, human-readable text format file. Provision is made for subclassing to alternate storage formats, and subclasses for Storable and Data::Denter are provided as examples. Although the Storable format may be somewhat faster than the default, the real reason for the override capability is to allow an actual, fast database to be used.

# .AUDIT FILES

Derived objects matching the Perl RE /\.AUDIT/i are ignored. These are presumed to be ``meta-DO's'' by convention, which aren't part of the build per se but rather pseudo-targets whose only purpose is to hold CR's which refer back to all real deliverables.

# CLASSIC CODE ANALYSIS COMPARED

Whouses can best be described by comparison with ``real'' impact analysis products. There are a number of full-scale tools on the market. Typically, these work by parsing the source code into some representation which they can then analyze. It's a powerful technique but entails some tradeoffs:

#### MINUSES

- A true code analysis tool must have knowledge of each programming language in use. I.e. to add support for Java, a Java parser must be added.

- A corollary of the above is that this tool requires lot of work by expert programmers. Thus the tools tend to be large, complex and expensive.

- Another corollary is that the tool must track each advance in each language, usually with significant lag time.

- Also, since analysis basically entails compiling the code, analysis of a large code base can take a long time, potentially as long or longer than actually building it.

- If some part of your application is written in a language the tool doesn't know (say Python or Visual Basic or Perl or an IDL), no analysis of that area can take place.

#### PLUSES

- The analysis can be as granular and as language-knowledgeable as its developers can make it. If you change the signature of a C function, it can tell you how many uses of that function, in what files and on what lines, will need to change.

- A code analysis tool may be tied to a set of languages but by the same token it's NOT tied to a particular SCM or build system.

The minuses above are not design flaws but inherent tradeoffs. For true code impact analysis you must buy one of these tools and accept the costs.

Whouses doesn't attempt code analysis per se. As noted above, true code analysis programs are tied to language but not to an SCM system. Whouses flips this around; it doesn't care about language but it only works with build systems that use clearmake, which is part of ClearCase.

# AUTHOR

David Boyce <dsb@boyski.com>

# COPYRIGHT

Copyright (c) 2000-2001 David Boyce. All rights reserved. This Perl program is free software; you may redistribute and/or modify it under the same terms as Perl itself.

# STATUS

This is currently ALPHA code and thus I reserve the right to change the UI incompatibly. At some point I'll bump the version suitably and remove this warning, which will constitute an (almost) ironclad promise to leave the interface alone.

# PORTING

I've tried to write this in a platform independent style but it has not been heavily tested on Windows (actually it hasn't been all that heavily tested anywhere). It does pass ``make test'' on Windows and appears to work fine in limited testing.

# SEE ALSO

perl(1), ClearCase::CRDB(3)