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## 8 Tools for use with Daikon

This chapter describes various tools that are included with the Daikon distribution.

Next: DtraceDiff utility, Up: Tools [Contents][Index]

### 8.1 Tools for manipulating invariants

This section gives information about tools that manipulate invariants (in the form of `.inv` files).

Next: MergeInvariants, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.1 Printing invariants

Daikon provides many options for controlling how invariants are printed. Often, you may want to print the same set of invariants several different ways. However, you only want to run Daikon once, since it may be very time consuming. The `PrintInvariants` utility prints a set of invariants from a `.inv` file.

`PrintInvariants` is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.PrintInvariants [flags] inv-file

`PrintInvariants` shares many flags with Daikon. These flags are only briefly summarized here. For more information about these flags, see Configuration options.

In particular, see the configuration options whose names start with `daikon.PrintInvariants`; see General configuration options.

`--help`

  Print usage message.

`--format name`

  Produce output in the given format. See Invariant syntax.

`--output filename`

  Send output to the specified file rather than `stdout`.

`--output_num_samples`

  Output numbers of values and samples for invariants and program points; for debugging.

`--ppt-select-pattern`

  Only outputs program points that match the specified regular expression

`--config filename`

  Load the configuration settings specified in the given file. See Configuration options, for details.

`--config_option name=value`

  Specify a single configuration setting. See Configuration options, for details.

`--dbg category`
`--debug`

  Enable debug loggers.

`--track class<var1,var2,var3>@ppt`

  Track information on specified invariant class, variables and program point. For more information, see Track logging in Daikon Developer Manual.

`--wrap_xml`

  Print extra info about invariants, and wrap in XML tags. This is primarily for programmatic use and for debugging. To add just the Java class of each invariant, use `--config_option daikon.PrintInvariants.print_inv_class=true`.

Next: Invariant Diff, Previous: Printing invariants, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.2 MergeInvariants

The `MergeInvariants` utility merges multiple serialized invariant files to create a single serialized invariant file that contains the invariants that are true across each of the input files. The results of merging N serialized invariant files should be the same as running Daikon on the N original `.dtrace` files.

`MergeInvariants` is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.MergeInvariants [flags]... file1 file2...

file1 and file2 are files containing serialized invariants produced by running Daikon. At least two invariant files must be specified.

`MergeInvariants` shares many flags with Daikon. These flags are only briefly summarized here. For more information about these flags, see Daikon configuration options.

`-h --help`

  Print usage message.

`-o inv_file`

  Output serialized invariants to the specified file; they can later be postprocessed, compared, etc. If not specified, the results are written to standard out.

`--config_option name=value`

  Specify a single configuration setting. See Configuration options, for details.

`--dbg category`

  Enable debug loggers.

`--track class<var1,var2,var3>@ppt`

  Track information on specified invariant class, variables and program point. For more information, see Track logging in Daikon Developer Manual.

Next: Annotate, Previous: MergeInvariants, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.3 Invariant Diff

The invariant diff utility is designed to output the differences between two sets of invariants. Invariant diff compares invariants at program points with the same name.

Invariant diff lets you compare the invariants generated by two versions of the same program, or compare the invariants generated by different runs of one program.

Invariant diff is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.diff.Diff [flags]... file1 [file2]

file1 and file2 are files containing serialized invariants produced by running Daikon or Diff with the `-o` flag. If file2 is not specified, file1 is compared with the empty set of invariants.

This section describes the optional flags.

`--help`

  Print usage message.

`-d`

  Display the tree of differing invariants (default). Invariants that are the same in file1 and file2 are not printed. At least one of the invariants must be justified. Does not print “uninteresting” invariants (currently some ‘`OneOf`’ and ‘`Bound`’ invariants).

`-a`

  Display the tree of all invariants. Includes invariants that are the same in file1 and file2, and unjustified invariants.

`-u`

  Include “uninteresting” invariants in the tree of differing invariants.

`-y`
`--ignore_unjustified`

  Include (statistically) unjustified invariants.

`-m`

  Compute (file1 - file2). This is all the invariants that appear in file1 but not file2. Unjustified invariants are treated as if they don’t exist. Output is written as a serialized ‘`InvMap`’ to the file specified with the `-o` option. To view the contents of the serialized ‘`InvMap`’, run `java daikon.diff.Diff file`.

`-x`

  Compute (file1 XOR file2). This is all the invariants that appear in one file but not the other. Unjustified invariants are treated as if they don’t exist. Output is written as a serialized ‘`InvMap`’ to the file specified with the `-o` option. To view the contents of the serialized ‘`InvMap`’, run `java daikon.diff.Diff file`.

`-n`

  Compute (file1 UNION file2). This is all the invariants that appear in either file. If the same invariant appears in both files, the one with the better justification is chosen. Output is written as a serialized ‘`InvMap`’ to the file specified with the `-o` option. To view the contents of the serialized ‘`InvMap`’, run `java daikon.diff.Diff file`.

`-o inv_file`

  Used in combination with the `-m` or `-x` option. Writes the output as a serialized ‘`InvMap`’ to the specified file.

`-p`

  Examine all program points. By default, only procedure entries and combined procedure exits are examined. This option also causes conditional program points to be examined.

`-e`

  Print empty program points. By default, program points are not printed if they contain no differences.

`--invSortComparator1 classname`
`--invSortComparator2 classname`
`--invPairComparator classname`

  Use the specified class as a custom comparator. A custom comparator can be used for any of 3 operations: sorting the first set of invariants, sorting the second set of invariants, and combining the two sets into the pair tree. The specified class must implement the Comparator interface, and accept objects of type Invariant.

`-v`

  Verbose output. Invariants are printed using the `repr()` method, instead of the `format()` method.

`-s`

  For internal use only. Display the statistics between two sets of invariants. The pairs of invariants are placed in bins according to the type of the invariant and the type of the difference.

`-t`

  For internal use only. Display the same statistics as `-s`, but as a tab-separated list.

`-j`

  For internal use only. Treat justification as a continuous value when gathering statistics. By default, justification is treated as a binary value — an invariant is either justified or it is not. For example, assume invariant ‘`I1`’ has a probability of .01, and ‘`I2`’ has a probability of .5. By default, this will be a difference of 1, since ‘`I1`’ is justified but ‘`I2`’ is not. With this option, this will be a difference of .49, the difference in the probabilities. This only applies when one invariant is justified, and the other is unjustified.

`-l`

  For debugging use only. Prints logging information describing the state of the program as it runs.

Next: AnnotateNullable, Previous: Invariant Diff, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.4 Annotate

The Annotate program inserts Daikon-generated invariants into Java source code as annotations in `DBC`, `ESC`, `Java` or `JML` format. These annotations are comments that can be automatically verified or otherwise manipulated by other tools. The Daikon website has an example of code after invariant insertion: http://plse.cs.washington.edu/daikon/StackAr.html.

Invoke Annotate like this:

    java -cp ${DAIKONDIR}/daikon.jar daikon.tools.jtb.Annotate Myprog.inv Myprog.java Myprog2.java ...

The first argument is a Daikon `.inv` or `.inv.gz` file produced by running Daikon with the `-o` command-line argument. All subsequent arguments are `.java` files. The original `.java` files are left unmodified, but Annotate produces new versions of the `.java` files (with names suffixed as `-escannotated`, `-jmlannotated`, or `-dbcannotated`) that include the Daikon invariants as comments.

The options are:

`--format name`

  Produce output in the given format. See Invariant syntax.

`--no_reflection`

  Do not use reflection to find information about the classes being instrumented. This allows Annotate to run without having access to the class files. Since the class files are necessary to generate ‘`also`’ tags, those tags will be left out when this option is chosen.

`--max_invariants_pp count`

  Output at most count invariants per program point (which ones are chosen is not specified).

`--wrap_xml`

  Each invariant is printed using the given format (`ESC`, `JML` or `DBC`), but the invariant expression is wrapped inside XML tags, along with other information about the invariant.

  For example, if this switch is set, the output format is `ESC`, and an invariant for method `foo(int x)` normally prints as

      /* requires x != 0; */

  Then the resulting output will look something like this (all in one line; we break it up here for clarity):

      /* requires <INVINFO>
      <INV> x != 0 </INV>
      <SAMPLES> 100 </SAMPLES>
      <DAIKON> x != 0 </DAIKON>
      <DAIKONCLASS> daikon.inv.unary.scalar.NonZero </DAIKONCLASS>
      <METHOD> foo() </METHOD>
      </INVINFO> ; */

  Note that the comment will no longer be a legal `ESC`/`JML`/`DBC` comment. To make it legal again, you must replace the XML tags with the string between the ‘`<INV>`’ tag.

  Also note the extra information printed with the invariant: the number of samples from which the invariant was inferred, the Daikon representation (i.e., the Daikon output format), the Java class that the invariant corresponds to, and the method that the invariant belongs to (`null` for object invariants).

If Annotate issues a warning message of the form

    Warning: Annotate: Daikon knows nothing about field ...

then the Annotate tool found a variable in the source code that was computed by Daikon. This can happen if Daikon was run omitting the variable, for instance due to `--std-visibility`. It can also happen due to a bug in Annotate or Daikon; if that is the case, please report it to the Daikon developers.

Next: Runtime-check instrumenter, Previous: Annotate, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.5 AnnotateNullable

By using the `AnnotateNullable` program, you can insert `@Nullable` annotations into your source code.

The purpose of `AnnotateNullable` is to make it easier to annotate programs for the Nullness Checker that is part of the Checker Framework. As background, the Nullness Checker warns the programmer about possible null dereference errors. This is useful, but it requires the programmer to write a `@Nullable` annotation anywhere that a variable might contain null. (An unannotated reference is assumed to never be null at run time.)

The `AnnotateNullable` tool automatically and soundly determines a subset of the proper `@Nullable` annotations, reducing the programmer’s burden. Each annotation that `AnnotateNullable` infers is correct. The programmer may need to write some additional `@Nullable` annotations, but that is much easier than writing them all.

To insert `@Nullable` annotations in your program, follow these steps:

1. Run your application one or more times to create a trace file. (It is not necessary to run DynComp.) The more thorough your test runs, the larger number of `@Nullable` annotations `AnnotateNullable` will produce.

       java -cp ${DAIKONDIR}/daikon.jar daikon.Chicory \
            --dtrace-file=an.dtrace.gz mypackage.MyClass arg1 arg2 ...

2. Run Daikon on the resulting `.dtrace` file:

       java -cp ${DAIKONDIR}/daikon.jar daikon.Daikon an.dtrace.gz --no_text_output \
           --config daikondir/java/daikon/annotate_nullable.config

3. Run the `AnnotateNullable` tool to create an annotation index file. `AnnotateNullable` writes its output to standard out, so you should redirect its output to a `.jaif` file.

       java -cp ${DAIKONDIR}/daikon.jar daikon.AnnotateNullable an.inv.gz > nullable-annotations.jaif

4. Use the Annotation File Utilities to insert the annotations in your `.class` or `.java` file.

       # To insert in class files:
       insert-annotations mypackage.MyClass nullable-annotations.jaif
       # To insert in source files:
       insert-annotations-to-source nullable-annotations.jaif \
           mypackage/MyClass.java annotated/mypackage/MyClass.java

`AnnotateNullable` is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.AnnotateNullable [flags] inv-file

The flags are:

`-n --nonnull-annotations`

  Adds ‘`NonNull`’ annotations as well as ‘`Nullable`’ annotations. Unlike ‘`Nullable`’ annotations, ‘`NonNull`’ annotations are not guaranteed to be correct.

Next: InvariantChecker, Previous: AnnotateNullable, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.6 Runtime-check instrumenter (runtimechecker)

The runtimechecker instrumenter inserts, into a Java file, instrumentation code that checks invariants as the program executes. For a full list of options, run:

    java -cp ${DAIKONDIR}/daikon.jar daikon.tools.runtimechecker.Main help

The `instrument` command to runtimechecker creates a new directory `instrumented-classes` containing a new version of the user-specified Java files, instrumented to check invariants at run time and to record a list of invariant violations in a Java data structure. You can compile and run the instrumented version of your program.

Here is an example of using the runtime-check instrumenter to create a version of file `ubs/BoundedStack.java` that checks the invariants in invariant file `BoundedStack.inv.gz`:

    java daikon.tools.runtimechecker.Main instrument BoundedStack.inv.gz \
        ubs/BoundedStack.java

The instrumented Java code references classes in the `daikon.tools.runtimechecker` package, so those classes must be present in the classpath when the instrumented classes are compiled and executed.

Invariants are evaluated at the program points at which they should hold. Three things can happen when evaluating an invariant:

- It evaluates to true, which means that the invariant holds. Program execution continues normally.
- It evaluates to false, which means that the invariant doesn’t hold. In this case the corresponding `daikon.tools.runtimechecker.Property` is added to a list in the class `daikon.tools.runtimechecker.Runtime`. A programmer can obtain the growing list of violated invariants through the method `daikon.tools.runtimechecker.Runtime.getViolations()`. (See that class for other useful methods.)
- A `Throwable` (exception) is thrown when evaluating the invariant. In this case, the throwable is added to the list `daikon.tools.runtimechecker.Runtime.internalInvariantEvaluationErrors`. The throwable is not rethrown.

Note that the instrumented program does not do anything with the list of violations; it merely creates the list. You will need to write your own code to process that list; see How to access violations.

Next: Problems compiling instrumented code, Up: Runtime-check instrumenter [Contents][Index]

#### 8.1.6.1 How to access violations

The instrumented class handles violations silently: it simply adds them to a list in the class `daikon.tools.runtimechecker.Runtime.` No “invariant violation” exceptions are thrown, and the violated invariants can only be obtained dynamically (while the program is running) by calling `daikon.tools.runtimechecker.Runtime.getViolations()`.

To obtain a file of all the violations for a program execution, you can use program `daikon.tools.runtimechecker.WriteViolationFile`. For example, if you usually run

    java MyProg arg1 arg2

then instead you would run

    java -cp myclasspath:${DAIKONDIR}/daikon.jar daikon.tools.runtimechecker.WriteViolationFile MyProg arg1 arg2

This will create a file called `violations.txt` in the current directory, immediately before the program exits normally. If the program under test calls `System.exit`, then no `violations.txt` file is created. (`JUnit` is an example of a program that calls `System.exit`.)

The following code snippet contains a method `callMethod()` which presumably calls one of the methods in the instrumented class. The code detects if any violations occurred, and if so, prints a message.

    daikon.tools.runtimechecker.Runtime.resetViolations();
    daikon.tools.runtimechecker.Runtime.resetErrors();

    callMethod();

    List<Violation> vs = daikon.tools.runtimechecker.Runtime.getViolations();

    if (!vs.isEmpty())
      System.out.println("Violations occurred.");

In addition, the instrumenter adds the following two methods to the instrumented class:

- `isDaikonInstrumented()`. Returns true (you could calling this method to see if the class has been instrumented).
- `getDaikonInvariants()`. Returns the array of properties being checked.

Previous: How to access violations, Up: Runtime-check instrumenter [Contents][Index]

#### 8.1.6.2 Problems compiling instrumented code

When compiling the instrumented code, the Java compiler might emit an error such as:

      error: longitude has private access in GeoPoint

If you receive the error above, then a variable in an invariant (longitude in this case) has been declared `private`.

There are two ways to fix this. To check invariants that mention private variables, supply the `--make_all_fields_public` command-line option when running ‘`java daikon.tools.runtimechecker.Main instrument ...`’. To ignore invariants that mention private variables, rebuild the `.dtrace` file by rerunning Chicory using the `--std-visibility` command-line option.

Another error the Java compiler might emit is:

      error: code too large for try statement

You get the above error if the combined size of the original source code, plus the instrumentation code, is larger than the JVM’s limit of 65536 bytes of bytecode per method.

You can correct the problem by using a smaller number of invariants when instrumenting. See Too much output.

(Eventually, it might be nice for the instrumenter to place its code in one or more separate methods so that no one of them is too large.)

Next: LogicalCompare, Previous: Runtime-check instrumenter, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.7 InvariantChecker

The `InvariantChecker` program takes a set of invariants found by Daikon and a set of data trace files. It checks each sample in the data trace files against each of the invariants. Any sample that violates an invariant is noted, via a message printed to standard output or to a specified output file.

`InvariantChecker` is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.tools.InvariantChecker [options] invariant-file dtrace-files

The invariant-files are invariant files (`.inv`) created by running Daikon. The dtrace-files are data trace (`.dtrace`) files created by running the instrumented program. The files may appear in any order; the file type is determined by whether the file name contains `.dtrace`, or `.inv`.

The options are:

`--help`

  Print usage message.

`--output output-file`

  Write any violations to the specified file.

`--conf`

  Checks only invariants that are above the default confidence level.

`--filter`

  Checks only invariants that are not filtered by the default filters.

`--verbose`

  Print all samples that violate an invariant. By default only the totals are printed.

`--dir directory-name`

  Processes all invariant files in the given directory and reports the number of invariants that failed on any of the `.dtrace` files in that directory. We only process invariants above the default confidence level and invariants that have not been filtered out by the default filters.

`--config_option name=value`
`--dbg category`
`--track class<var1,var2,var3>@ppt`

  These switches are the same as for Daikon. They are described in Running Daikon.

Previous: InvariantChecker, Up: Tools for manipulating invariants [Contents][Index]

#### 8.1.8 LogicalCompare

Suppose you have two sets of invariants describing the operation of a software module or describing two implementations of a module with the same interface. Roughly, one set of invariants is “stronger” than another if in any situation where the “stronger” invariants hold, the “weaker” invariants also hold. The `LogicalCompare` tool checks whether two sets of invariants satisfy this relationship.

In order to use `LogicalCompare`, Simplify must be installed (see Installing Simplify).

An invocation of `LogicalCompare` has the following form:

    java -cp ${DAIKONDIR}/daikon.jar daikon.tools.compare.LogicalCompare [options] \
        weak-invs strong-invs [enter-ppt [exit-ppt]]

The `LogicalCompare` program takes two mandatory arguments, which are `.inv` files containing invariants. `LogicalCompare` checks whether the invariants in the first file are weaker (implied by) the invariants in the second file. `LogicalCompare` prints any exceptions to this implication, preceded by the text “Invalid:”.

To be precise, for each pair of program points representing a single method or function, `LogicalCompare` will check that each precondition (`:::ENTER` point invariant) in the “stronger” invariant set is implied by some combination of invariants in the “weaker” invariant set, and that each postcondition (`:::EXIT` point invariant) in the “weaker” invariant set is implied by some combination of postconditions in the “stronger” set and preconditions in the “weaker” set.

If no other regular arguments besides the two `.inv` files are supplied, all the method or function program points that exist in both files will be compared, with a exception message reported for each method that exists in the “weaker” set but not the “stronger”. Alternatively, one or two additional arguments may be supplied, which name an `:::ENTER` program point and an `:::EXIT` program point to examine (if only an `:::ENTER` program point is supplied, the corresponding combined `:::EXIT` point is selected automatically).

`LogicalCompare` accepts the following options:

`--assume file`

  Read additional assumptions about the behavior of compared routines from the file file. The assumptions file should consist of lines starting with ‘`PPT_NAME`’, followed by the complete name of an `:::ENTER` program point, followed by lines each consisting of a Simplify formula, optionally followed by a `#` and a human-readable annotation. Blank lines and lines beginning with a `#` are ignored. The assumption properties will be used as if they were invariants true at the strong `:::EXIT` point when checking weak `:::EXIT` point invariants.

`--config_option option=value`

  Specify a single configuration setting. The available settings are the same as can be passed to Daikon’s `--config_option` option, though because the invariants have already been generated, some will have no effect. For a list of available options, see Configuration options.

`--config-file=file`

  Read configuration options from the file file. This file should have the same format as one passed to Daikon’s `--config` option, though because the invariants have already been generated, some will have no effect.

`--debug`
`--dbg category`

  These options have the same effect as the `--debug` and `--dbg` options to Daikon, causing debugging logs to be printed.

`--filters=[bBoOmjpi]`

  Control which invariants are removed from consideration before implications are checked. Note that except as controlled by this option, `LogicalCompare` does not perform any of the filters that normally control whether invariants are printed by Daikon. Also, invariants that cannot be formatted for the Simplify automatic theorem prover will be discarded in any case, as there would be no other way to process them. Each letter controls a filter: an invariant is rejected if it is rejected by any filter (or, equivalently, kept only if it passes through every filter).

  `b`

    Discard upper-bound and lower-bound invariants (such as ‘`x <= c`’ and ‘`x >= c`’ for a constant c), when Daikon considers the constant to be uninteresting. Currently, Daikon has a configurable range of interesting constant: by default, -1, 0, 1, and 2 are interesting, and no other numbers are.

  `B`

    Discard all bound invariants, whether or not the constants in them are considered interesting.

  `o`

    Discard ‘`one-of`’ invariants (which signify that a variable always had one of a small set of values at run time), when the values that the variable took are considered uninteresting by Daikon.

  `O`

    Discard all ‘`one-of`’ invariants, whether or not the values involved are interesting.

  `m`

    Discard invariants for which it was never the case that all the variables involved in the invariant were present at the same time.

  `j`

    Discard invariants that Daikon determines to be statistically unjustified, according to its tests.

  `p`

    Discard invariants that refer to the values of pass-by-value parameters in the postcondition, or to the values of objects pointed to by parameters in postconditions, when the pointer is not necessarily the same as at the entrance to the method or function. Usually such invariants reflect implementation details that would not be visible to the caller of a method.

  `i`

    Discard implication invariants when they appear in `:::ENTER` program points.

  The default set of filters corresponds to the letters `ijmp`.

`--help`

  Print a brief summary of available command-line options.

`--no-post-after-pre-failure`

  If implication is not verified between two invariant sets after examining the preconditions, do not continue to check the implication involving postconditions. Because the postconditions aren’t formally meaningful outside the domain specified by the preconditions, this is the safest behavior, but in practice trivial precondition mismatches may prevent an otherwise meaningful postcondition comparison. See also `--post-after-pre-failure`.

`--proofs`

  For each implication among invariants that is verified, print a minimal set of conditions that establish the truth of the conclusion. The set is minimal, in the sense that if any condition were removed, the conclusion would no longer logically follow according to Simplify, but it is not the least such set: there may exist a smaller set of conditions that establish the conclusion, if that set is not a subset of the set printed. Beware that because this option uses a naive search technique, it may significantly slow down output.

`--post-after-pre-failure`

  Even if implication is not verified between two invariant sets after examining the preconditions, continue to check the implication involving postconditions. This is somewhat dangerous, in that if the implication does not hold between the preconditions, the invariant sets may be inconsistent, in which case reasoning about the postconditions is formally nonsensical, but the tool will attempt to ignore the contradiction and carry on in this case. This is now the default behavior, so the option has no effect, but it is retained for backward compatibility. See also `--no-post-after-pre-failure`.

`--show-count`

  Print a count of the number of invariants checked for implication.

`--show-formulas`

  For each invariant, show how it is represented as a logical formula passed to Simplify.

`--show-sets`

  Rather than testing implications among invariants, simply print the sets of weak and strong `:::ENTER` and `:::EXIT` point invariants that would normally be compared. The invariants are selected and filtered as implied by other options.

`--show-valid`

  Print invariants that are verified to be implied (“valid”), as well as those for which the implication could not be verified (“invalid” invariants, which are always printed).

`--timing`

  For each set of invariants checked, print the total time required for the check. This time includes both processing done by `LogicalCompare` directly, and time spent waiting for processing done by Simplify, but does not include time spent deserializing the `.inv` input files.

Next: Reading dtrace files, Previous: Tools for manipulating invariants, Up: Tools [Contents][Index]

### 8.2 DtraceDiff utility

`DtraceDiff` is a utility for comparing data trace (`.dtrace`) files. It checks that the same program points are visited in the same order in both files, and that the number, names, types, and values of variables at each program point are the same. The differences are found using a content-based, rather than text-based, comparison of the two files.

`DtraceDiff` stops by signaling an error when it finds a difference between the two data trace files. (Once execution paths have diverged, continuing to emit record-by-record differences is likely to produce output that is far too voluminous to be useful.) It also signals an error when it detects incompatible program point declarations or when one file is shorter than the other.

`DtraceDiff` is invoked as follows:

    java -cp ${DAIKONDIR}/daikon.jar daikon.tools.DtraceDiff [flags] \
       [declsfiles1] dtracefile1  [declsfiles2] dtracefile2

Corresponding declarations (`.decls`) files can optionally be specified on the command line before each of the two `.dtrace` files. Multiple `.decls` files can be specified. If no `.decls` file is specified, `DtraceDiff` assumes that the declarations are included in the `.dtrace` file instead.

`DtraceDiff` supports the following Daikon command-line flags:

`--help`

  Print usage message.

`--config filename`

  Load the configuration settings specified in the given file. See Configuration options, for details.

`--config_option name=value`

  Specify a single configuration setting. See Configuration options, for details.

`--ppt-select-pattern=ppt_regexp`

  Only process program points whose names match the regular expression.

`--ppt-omit-pattern=ppt_regexp`

  Do not process program points whose names match the regular expression. This takes priority over the `--ppt-select-pattern` argument.

`--var-select-pattern=ppt_regexp`

  Only process variables (whether in the trace file or derived) whose names match the regular expression.

`--var-omit-pattern=var_regexp`

  Ignore variables (whether in the trace file or derived) whose names match the regular expression, which uses Perl syntax. This takes priority over the `--var-select-pattern` argument.

`DtraceDiff` uses appropriate comparisons for the type of the variables in each program point being compared. In particular:

- Hashcode (pointer or address) values may differ from one run of the same program to the next, and there may not be a one-to-one mapping of hashcode values between different program executions, so the comparison function only looks for null versus non-null pointer values.
- Floating-point values are subject to roundoff error from printing and reading, so they are compared with a “fuzzy” rather than exact equality test.

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### 8.3 Reading dtrace files

If you wish to write a program that manipulates `.dtrace` files, then see See Reading dtrace files in Daikon Developer Manual.

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