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Detecting invariants involves two steps:
This section briefly describes how to obtain data traces for Java, C, C#, Perl, and Eiffel programs, and how to run Daikon. For detailed information about these and other front ends that are available for Daikon, see Front ends and instrumentation.
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Before detecting invariants in Java programs, you must run
make -C $DAIKONDIR/java dcomp_rt.jar
(for more details, see Instrumenting the JDK with DynComp).
In order to detect invariants in a Java program, you will run the program twice — once using DynComp (see DynComp for Java) to create a .decls file and once using Chicory (see Chicory) to create a data trace file. Then, run Daikon on the data trace file to detect invariants. With the --daikon option to Chicory, a single command performs the last two steps.
For example, if you usually run
java -cp myclasspath mypackage.MyClass arg1 arg2 arg3
then instead you would run these two commands:
java -cp myclasspath:$DAIKONDIR/daikon.jar daikon.DynComp mypackage.MyClass arg1 arg2 arg3 java -cp myclasspath:$DAIKONDIR/daikon.jar daikon.Chicory --daikon \ --comparability-file=MyClass.decls-DynComp \ mypackage.MyClass arg1 arg2 arg3
and the Daikon output is written to the terminal.
• StackAr example | ||
• Detecting invariants when running a Java program from a jar file | ||
• Understanding the invariants | ||
• Second Java example |
Next: Detecting invariants when running a Java program from a jar file, Up: Detecting invariants in Java programs [Contents][Index]
The Daikon distribution contains some sample programs that will help you get practice in running Daikon.
To detect invariants in the StackAr sample program, perform the following steps after installing Daikon (see Installing Daikon).
cd examples/java-examples/StackAr javac -g DataStructures/*.java
java -cp .:$DAIKONDIR/daikon.jar daikon.DynComp DataStructures.StackArTester
java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory --daikon \ --comparability-file=StackArTester.decls-DynComp \ DataStructures.StackArTester
Alternately, replacing the --daikon argument by --daikon-online has the same effect, but does not write a data trace file to disk.
If you wish to have more control over the invariant detection process, you can split the third step above into multiple steps. Then, step 3 would become:
java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory \ --comparability-file=StackArTester.decls-DynComp \ DataStructures.StackArTester
java -cp $DAIKONDIR/daikon.jar daikon.Daikon StackArTester.dtrace.gz
There are various ways to do this.
PrintInvariants
program to display the invariants.
java -cp $DAIKONDIR/daikon.jar daikon.PrintInvariants StackArTester.inv.gz
For more options to the PrintInvariants
program, see Printing invariants.
java -cp .:$DAIKONDIR/daikon.jar daikon.tools.jtb.Annotate StackArTester.inv.gz \ DataStructures/StackAr.java
Now examine file DataStructures/StackAr.java-escannotated. For more information about the Annotate program, see Annotate.
Daikon can analyze multiple runs (executions) of the program. You can supply Daikon with multiple trace files:
java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory \ --dtrace-file=StackArTester1.dtrace.gz \ --comparability-file=StackArTester.decls-DynComp DataStructures.StackArTester java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory \ --dtrace-file=StackArTester2.dtrace.gz \ --comparability-file=StackArTester.decls-DynComp DataStructures.StackArTester java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory \ --dtrace-file=StackArTester3.dtrace.gz \ --comparability-file=StackArTester.decls-DynComp DataStructures.StackArTester java -cp $DAIKONDIR/daikon.jar daikon.Daikon StackArTester*.dtrace.gz
(In this example, all the runs are identical, so multiple runs yield the same invariants as one run.)
Next: Understanding the invariants, Previous: StackAr example, Up: Detecting invariants in Java programs [Contents][Index]
If your Java program is run directly from a jar file, such as either of:
java mypackage.jar arguments java -cp myclasspath mypackage.jar arguments
then to detect invariants in that Java program, run these two commands:
java -cp myclasspath:$DAIKONDIR/daikon.jar daikon.DynComp <MyMain> arguments java -cp myclasspath:$DAIKONDIR/daikon.jar daikon.Chicory --daikon \ --comparability-file=<MyMain>.decls-DynComp <MyMain> arguments
where <MyMain>
is the Main-class of the jar file, which you
can determine by running the command:
unzip -p mypackage.jar META-INF/MANIFEST.MF | grep '^Main-Class:'
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This section examines some of the invariants for the StackAr example. For more help interpreting invariants, see Interpreting output.
The StackAr example is an array-based stack implementation. Take a look at DataStructures/StackAr.java to get a sense of the implementation. Now, look at the sixth section of Daikon output.
====================================================================== StackAr:::OBJECT this.theArray != null this.theArray.getClass().getName() == java.lang.Object[].class this.topOfStack >= -1 this.topOfStack <= size(this.theArray[])-1 ======================================================================
These four annotations describe the representation invariant. The
array is never null, and its run-time type is Object[]
. The
topOfStack
index is at least -1 and is less than the length
of the array.
Next, look at the invariants for the top()
method.
top()
has two different exit points, at lines 74 and 75
in the original source. There is a set of invariants for each exit
point, as well as a set of invariants that hold for all exit points.
Look at the invariants when top()
returns at line 75.
====================================================================== StackAr.top():::EXIT75 return == this.theArray[this.topOfStack] return == this.theArray[orig(this.topOfStack)] return == orig(this.theArray[post(this.topOfStack)]) return == orig(this.theArray[this.topOfStack]) this.topOfStack >= 0 return != null ======================================================================
The return value is never null, and is equal to the array element at
index topOfStack
. The top of the stack is at least 0.
Previous: Understanding the invariants, Up: Detecting invariants in Java programs [Contents][Index]
A second example is located in the examples/java-examples/QueueAr subdirectory. Run this sample using the following steps:
cd examples/java-examples/QueueAr javac -g DataStructures/*.java
java -cp .:$DAIKONDIR/daikon.jar daikon.DynComp DataStructures.QueueArTester java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory --daikon \ --comparability-file=QueueArTester.decls-DynComp \ DataStructures.QueueArTester
Alternately, you can split the very last command into two parts:
java -cp .:$DAIKONDIR/daikon.jar daikon.Chicory \ --comparability-file=QueueArTester.decls-DynComp \ DataStructures.QueueArTester
java -cp $DAIKONDIR/daikon.jar daikon.Daikon QueueArTester.dtrace.gz
Next: Detecting invariants in C# programs, Previous: Detecting invariants in Java programs, Up: Example usage [Contents][Index]
In order to detect invariants over C or C++ programs, you must first install a C/C++ front end (instrumenter). We recommend that you use Kvasir (see Kvasir), and this section gives examples using Kvasir. By default, Kvasir also runs the DynComp tool to improve Daikon’s performance and Daikon’s output by filtering out invariants involving unrelated variables (see DynComp for C/C++).
To use the C/C++ front end Kvasir with your program, first compile your
program.
(If you use gcc
to compile your program, use the following
command-line arguments: -gdwarf-2 -no-pie.
Also use -fno-stack-clash-protection if your gcc
supports it.
Note that if your build system separates the
compile and link steps, then -no-pie needs to be on the link
step.)
Then, run your program as usual, but prepend
kvasir-dtrace
to the command line.
Kvasir will produce two output files: a .dtrace file containing a trace of a particular execution, and a .decls file that contains information about what variables and functions exist in a program, along with information grouping the variables into abstract types. You will supply both of these files to Daikon.
For more information about Kvasir, including more detailed documentation on its command-line options, see Kvasir.
• C examples | ||
• Dealing with large examples |
The Daikon distribution comes with several example C programs to enable users to become familiar with running Daikon on C programs. These examples are located in the examples/c-examples directory.
To detect invariants for a program with Kvasir, you need to perform two basic tasks: run the program under Kvasir to create a trace and declaration files (steps 1–3), and run Daikon over these files to produce invariants (step 4). The following instructions are for the wordplay example, which is a program for finding anagrams.
cd $DAIKONDIR/examples/c-examples/wordplay
gcc -gdwarf-2 -no-pie wordplay.c -o wordplay
Kvasir can also be used for programs constructed by compiling a number of .c files separately, and then linking them together; in such a program, specify -gdwarf-2 when compiling each source file containing code you wish to see invariants about.
kvasir-dtrace
to the command line.
kvasir-dtrace ./wordplay -f words.txt 'Daikon Dynamic Invariant Detector'
Any options to the program can be specified as usual; here, for instance, we give commands to look for anagrams of the phrase “Daikon Dynamic Invariant Detector” using words from the file words.txt.
Executing under Kvasir, the program runs normally, but Kvasir executes additional checks and collects trace information (for this reason, the program will run more slowly than usual). Kvasir creates a directory named daikon-output under the current directory, and creates the wordplay.dtrace file, which lists variable values, and the wordplay.decls file that contains information about what variables and functions exist in a program, along with information grouping the variables into abstract types.
Kvasir will also print messages if it observes your program doing something with undefined effects; these may indicate bugs in your program, or they may be spurious. (If they are bugs, they can also be tracked down by using Valgrind (https://valgrind.org/) with its regular memory checking tool; if they do not appear with that tool, they are probably spurious).
java -cp $DAIKONDIR/daikon.jar daikon.Daikon \ --config_option daikon.derive.Derivation.disable_derived_variables=true \ daikon-output/wordplay.decls daikon-output/wordplay.dtrace
The invariants are printed to standard output, and a binary representation of the invariants is written to wordplay.inv.gz. Note that the example uses a configuration option to disable the use of derived variables; it can also run without that option, but takes significantly longer.
Daikon can analyze multiple runs (executions) of the program. You can supply Daikon with multiple trace files:
kvasir-dtrace --dtrace-file=daikon-output/wordplay1.dtrace \ ./wordplay -f words.txt 'daikon dynamic invariant detector' kvasir-dtrace --no-dyncomp --dtrace-file=daikon-output/wordplay2.dtrace \ ./wordplay -f words.txt 'better results from multiple runs' kvasir-dtrace --no-dyncomp --dtrace-file=daikon-output/wordplay3.dtrace \ ./wordplay -f words.txt 'more testing equals better testing' java -Xmx3600m -cp $DAIKONDIR/daikon.jar daikon.Daikon \ daikon-output/wordplay*.dtrace daikon-output/wordplay.decls
Note that this example makes the assumption that the DynComp .decls information
for wordplay
does not vary from run to run.
Thus it specifies --no-dyncomp on subsequent runs to improve performance.
(This assumption may not be true for other programs.)
Alternatively, you can append information from multiple runs in a single trace file:
kvasir-dtrace --dtrace-file=daikon-output/wordplay-all.dtrace \ ./wordplay -f words.txt 'daikon dynamic invariant detector' kvasir-dtrace --no-dyncomp --dtrace-append \ --dtrace-file=daikon-output/wordplay-all.dtrace \ ./wordplay -f words.txt 'better results from multiple runs' kvasir-dtrace --no-dyncomp --dtrace-append \ --dtrace-file=daikon-output/wordplay-all.dtrace \ ./wordplay -f words.txt 'more testing equals better testing' java -Xmx3600m -cp $DAIKONDIR/daikon.jar daikon.Daikon \ daikon-output/wordplay-all.dtrace daikon-output/wordplay.decls
PrintInvariants
program to display the invariants.
For help understanding the invariants, see Interpreting output.
There is a second example C program in the bzip2 directory.
It may be run in a similar fashion as the wordplay example,
but it is a more complex program and the kvasir-dtrace
step may take several minutes.
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Since the default memory size used by a Java virtual machine varies, we suggest that Daikon be run with at least 256 megabytes of memory (and perhaps much more). For many JVMs, specify a maximum heap size of 3.6GB by the option -Xmx3600m. For more information about specifying the memory usage for Daikon, see Out of memory.
Disk usage can be reduced by specifying that the front end should compress its output .dtrace files.
In some cases, the time and space requirements of the examples can be reduced by reducing the length of the program run. However, Daikon’s running time depends on both the length of the test run and the size of the program data (such as its use of global variables and nested data structures). The examples also demonstrate disabling derived variables, which significantly improves Daikon’s performance at the cost of producing fewer invariants. For more techniques for using Daikon with large programs and long program runs, see Large dtrace files.
Next: Detecting invariants in Perl programs, Previous: Detecting invariants in C/C++ programs, Up: Example usage [Contents][Index]
The Daikon front end for .NET languages (C#, F#, and Visual Basic) is called Celeriac.
Please see its documentation at https://github.com/codespecs/daikon-dot-net-front-end.
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The Daikon front end for Perl is called dfepl
.
Using the Perl front end is a two-pass process: first you must run the annotated program so that the runtime system can dynamically infer the kind of data stored in each variable, and then you must re-annotate and re-run the program with the added type information. This is necessary because Perl programs do not contain type declarations.
dfepl
requires version 5.8 or later of Perl.
• Instrumenting Perl programs | ||
• Perl examples |
Next: Perl examples, Up: Detecting invariants in Perl programs [Contents][Index]
Perl programs must be instrumented twice. First they must be instrumented without type information. Then, once the first instrumented version has been run to produce type information, they must be instrumented again taking the type information into account.
To instrument a stand-alone Perl program, invoke dfepl
with
the name of the program as an argument.
dfepl program.pl
To instrument a Perl module or a collection of modules, invoke
dfepl
either with the name of each module, or with the name
of a directory containing the modules. To instrument all the modules
in the current directory, give dfepl
the argument ..
For instance, if the current directory contains a module
Acme::Trampoline
in Acme/Trampoline.pm and another
module Acme::Date
in Acme/Date.pm, they can be annotated
by either of the following two commands:
dfepl Acme/Trampoline.pm Acme/Date.pm dfepl .
Once type information is available, run the instrumentation command again with the -T or -t options added to use the produced type information.
For more information about dfepl
, see dfepl.
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The Daikon distribution includes sample Perl programs suitable for use with Daikon in the examples/perl-examples directory.
Here are step-by-step instructions for examining a simple module, Birthday.pm, as used by a test script test-bday.pl.
cd examples/perl-examples
dfepl Birthday.pm
This command creates a directory daikon-untyped, and puts the instrumented version of Birthday.pm into daikon-untyped/Birthday.pm. As the directory name implies, this instrumented version doesn’t contain type information.
dtype-perl test_bday.pl 10
The dtype-perl is a script that runs Perl with the appropriate command line options to find the modules used by the Daikon Perl runtime tracing modules, and to use the instrumented versions of modules in daikon-untyped in preference to their original ones. The number 10 is an argument to the test_bday.pl script telling it to run a relatively short test.
This will also generate a file daikon-instrumented/Birthday.types recording the type of each variable seen during the execution of the instrumented program.
dfepl -T Birthday.pm
This step repeats step 2, except that the -T flag to
dfepl
tells it to use the type information generated in the
previous step, and to put the output in the directory
daikon-instrumented. dfepl
also converts the
type information into a file daikon-output/Birthday.decls
containing subroutine declarations suitable for Daikon.
dtrace-perl test_bday.pl 30
Here we run another test suite, which happens to be the same
test_bday.pl, but running for longer. (The example will also
work with a smaller number). The script dtrace-perl
is
similar to dtype-perl
mentioned earlier, but looks for
instrumented source files in daikon-instrumented.
This creates daikon-output/test_bday-combined.dtrace, a trace file containing the values of variables at each invocation. (The file name is formed from the name of the test program, with -combined appended because it contains the trace information from all the instrumented modules invoked from the program).
cd daikon-output
java -cp $DAIKONDIR/daikon.jar daikon.Daikon Birthday.decls test_bday-combined.dtrace
PrintInvariants
program and other Daikon tools.
For example:
java -cp $DAIKONDIR/daikon.jar daikon.PrintInvariants Birthday.inv.gz
Invariants produced from Perl programs can be examined using the same tools as other Daikon invariants.
In the example above, the script test_bday.pl was not itself instrumented; it was only used to test the instrumented code. The Perl front end can also be used to instrument stand-alone Perl programs. The following sequence of commands, similar to those above, show how Daikon can be used with the stand-alone program standalone.pl, also in the examples/perl-examples directory.
dfepl standalone.pl dtype-perl daikon-untyped/standalone.pl dfepl -T standalone.pl dtrace-perl daikon-instrumented/standalone.pl cd daikon-output java -cp $DAIKONDIR/daikon.jar daikon.Daikon -o standalone.inv standalone-main.decls \ standalone-combined.dtrace
Note two differences when running a stand-alone program. First, the
instrumented versions of the program, in the daikon-untyped or
daikon-instrumented directory, are run directly. Second, the
declarations file is named after the package in which the subroutines
were declared, but since every stand-alone program uses the
main
package, the name of the program is prepended to the
.decls file name to avoid collisions.
Next: Detecting invariants in Simulink/Stateflow programs, Previous: Detecting invariants in Perl programs, Up: Example usage [Contents][Index]
CITADEL is an Eiffel front-end to the Daikon invariant detector. You can obtain Citadel from https://se.inf.ethz.ch/people/polikarpova/citadel/.
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Hynger (HYbrid iNvariant GEneratoR) instruments Simulink/Stateflow (SLSF) block diagrams to generate Daikon input (.dtrace files). Hynger was created by Taylor Johnson, Stanley Bak, and Steven Drager. You can obtain Hynger from https://github.com/verivital/hynger.
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