version : @(#)jvm.jcov.txt 1.1 99/06/22 JCOV support in JDK1.3 Up to JDK1.2.x Jcov runtime support has been an integral part of the debug version of the Javasoft's JVM, therefore it could not work with any other JVMs. In JDK1.3 all Jcov support was isolated in a separate library and implemented basing upon the Java Virtual Machine Profiler Interface (JVMPI), so it theoretically can work with any JVM that support JVMPI. This library is loaded by a JVM at its startup, if the -Xrunjcov option is specified. For more information about how JVM finds and loads libraries passed via the -Xrun JVM's option, please consult JVMPI docs. usage: java [other java options] -Xrunjcov[:][help]|[=, ...] classname where is the name of an option, is its value. The recognized command-line options are : include= makes Jcov profile only those classes whose names begin with given class name prefix. This option may be specified multiple times - in this case class name must satisfy at least one of the class name prefixes to be profiled. exclude= tells Jcov not to profile classes whose names begin with given class name prefix. This option may be given multiple times - if a class name satisfies at least one of the class name prefixes then it will not be profiled. type= value can be either B or M. Sets jcov data gathering mode : in B mode method/block/branch coverage data is gathered, in M only method coverage data is gathered. Default value is B. file= specifies savefile name, default - java.jcov. Example 1. > java -Xrunjcov class This command will make Jcov profile all loaded classes which have the CoverageTable class attribute (i.e. all loaded classes which had been compiled with the -Xjcov compiler option) and save method/block/branch coverage data to a file named java.jcov in current directory. Example 2. > java -Xrunjcov:include=java,exclude=java.lang,exclude=java.io,type=M,file=/tmp/sys.jcov class This command will make Jcov profile all classes from the java package and its subpackages except java.lang and java.io, only method coverage statistics will be gathered and saved to a file named sys.jcov' in the /tmp directory. Note that 1.JVM must not be run in debug mode (-Xdebug option must not be specified), since Jcov cannot work correctly in this JVM's mode. 2.When gathered data is saved to an existing Jcov data file, then it is merged (on per-class basis) with the corresponding data found in the file. If the data types of two classes being merged don't match, then both classes are saved in the resulting jcov data file. 3.For Jcov to work correctly any JIT compiler must be turned off (for example, by specifying the -Djava.compiler=NONE JVM's option) 4.If a class or an interface contains only abstract methods then it will not be profiled at all (i.e. no code coverage data will be gathered for it). 5.Only non-abstract methods are profiled. 6.If data gathering mode is set to B then those classes, having no CoverageTable class attribute, will not be profiled. 7.For Jcov to be able to gather block/branch coverage data for a certain class, this class must have CoverageTable class attribute. This can be achived by compiling this class with the -prof=jcov (JDK1.1 - JDK 1.1.x) option or the -Xjcov (JDK1.2 - JDK 1.2.x) option.