Suppress warnings from CPD for C/C++ code

Question

We are using PMD Copy Paste Detector (CPD) to analyze our C and C++ code. However, there are a few parts of the code that are very similar, but with a good reason and we would like to suppress the warnings for these parts.

The documentation of PMD CPD only mentions something about annotations, but this will not work for our these languages.

How can I still ignore warnings for specific parts?

Is there a comment to do so perhaps?

[UPDATE] I'm using the following Groovy script to run CPD:

@GrabResolver(name = 'jcenter', root = 'https://jcenter.bintray.com/')
@Grab('net.sourceforge.pmd:pmd-core:5.4.+')
@Grab('net.sourceforge.pmd:pmd-cpp:5.4.+')
import net.sourceforge.pmd.cpd.CPD
import net.sourceforge.pmd.cpd.CPDConfiguration
import java.util.regex.Pattern

def tokens = 60
def scanDirs = ['./path/to/scan', './scan/this/too']
def ignores = [
    './ignore/this/path',
    './this/must/be/ignored/too'
    ].collect({ it.replace('/', File.separator) })
def rootDir = new File('.')
def outputDir = new File('./reports/analysis/')

def filename_date_format = 'yyyyMMdd'
def encoding = System.getProperty('file.encoding')
def language_converter = new CPDConfiguration.LanguageConverter()
def config = new CPDConfiguration()
config.language = new CPDConfiguration.LanguageConverter().convert('c')
config.minimumTileSize = tokens
config.renderer = config.getRendererFromString 'xml', 'UTF-8'
config.skipBlocksPattern = '//DUPSTOP|//DUPSTART'
config.skipLexicalErrors = true
def cpd = new CPD(config)

scanDirs.each { path ->
    def dir = new File(path);
    dir.eachFileRecurse(groovy.io.FileType.FILES) {
        // Ignore file?
        def doIgnore = false
        ignores.each { ignore ->
            if(it.path.startsWith(ignore)) {
                doIgnore = true
            }
        }
        if(doIgnore) {
            return
        }

        // Other checks
        def lowerCaseName = it.name.toLowerCase()
        if(lowerCaseName.endsWith('.c') || lowerCaseName.endsWith('.cpp') || lowerCaseName.endsWith('.h')) {
            cpd.add it
        }
    }
}

cpd.go();

def duplicationFound = cpd.matches.hasNext()

def now = new Date().format(filename_date_format)
def outputFile = new File(outputDir.canonicalFile, "cpd_report_${now}.xml")
println "Saving report to ${outputFile.absolutePath}"

def absoluteRootDir = rootDir.canonicalPath
if(absoluteRootDir[-1] != File.separator) {
    absoluteRootDir += File.separator
}

outputFile.parentFile.mkdirs()
def xmlOutput = config.renderer.render(cpd.matches);
if(duplicationFound) {
  def filePattern = "(<file\\s+line=\"\\d+\"\\s+path=\")${Pattern.quote(absoluteRootDir)}([^\"]+\"\\s*/>)"
  xmlOutput = xmlOutput.replaceAll(filePattern, '$1$2')
} else {
  println 'No duplication found.'
}

outputFile.write xmlOutput

Answer 1

I know this is a ~3 years old question, but for completeness, CPD started supporting this in PMD 5.6.0 (April 2017) in Java, and since 6.3.0 (April 2018) it has been extended to many other languages such as C/C++. Nowadays, almost all CPD supported languages allow for comment-based suppressions.

The complete (current) docs for comment-based suppression are available at https://pmd.github.io/pmd-6.13.0/pmd_userdocs_cpd.html#suppression

It's worth noting, if a file has a // CPD-OFF comment, but no matching // CPD-ON, everything will be ignored until the end of file.

Answer 2

After searching through the code of PMD on GitHub, I think I can safely say that this is NOT supported at this point in time (current version being PMD 5.5.0).

A search for CPD-START in their repository, does not show any results within the pmd-cpp directory (see the search results on GitHub).

Answer 3

You can define your custom markers for excluding certain blocks from analysis through the --skip-blocks-pattern option.

--skip-blocks-pattern Pattern to find the blocks to skip. Start and End pattern separated by |. Default is #if 0|#endif.

For example the following will ignore blocks between /* SUPPRESS CPD START */ and /* SUPPRESS CPD END */ comments (the comment must occupy a separate line):

$ ./run.sh cpd --minimum-tokens 100 --files /path/to/c/source --language cpp ----skip-blocks-pattern '/* SUPPRESS CPD START */|/* SUPPRESS CPD END */'

Note however, that this will cause the tool perform copy-paste-detection inside code delimited by #if 0/#endif.

Answer 4

I don't have any help for CPD. In general, I know about such tools; I don't understand the bit about "warnings".

Our CloneDR tool finds exact and near-miss duplicate code. IMHO, it finds better clones than CPD, because it uses the language syntax/ structure as a guide. [This fact is backed up by a research report done by a third party that you can find at the site]. And it does not issue "warnings".

If there is code that it thinks is involved in a clone, the tool will generate an output report page for the clones involved. But that isn't a warning. There is no way to suppress the reporting behavior. Obviously, if you have seen such a clone and decide it is not interesting, you can mark one of the clone entries with a comment stating that it is an uninteresting clone; that comment will show up in the clone report. (Such) comments have no impact whatsover on what clones are detected by CloneDR, so adding them does not change the computed answer.