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.