There were remaining assignments that were tricker to get to, now I've updated my script:

{
        macros[1] = "NSK_VERIFY"
        macros[2] = "NSK_JNI_VERIFY"
        macros[3] = "NSK_JVMTI_VERIFY"

        indentation = gensub(/([ ]*).*/, "\\1" , "g", $0)
        #print "Indent: " indentation "-"

        pattern = ".*NULL)(.*)"
        suffix = gensub(pattern, "\\1" , "g", $0)

        comparator = gensub(/.* (..) NULL.*/, "\\1", "g", $0)

        for (m in macros) {
                macro = macros[m]

                pattern = macro "((.* = .* .. NULL))"
                if ($0 ~ pattern) {
                        pattern = "(.*" macro "\\().*"
                        prefix = gensub(pattern, "\\1", "g", $0)

                        #print "Prefix: " prefix

                        pattern = ".*" macro "\\([^\\(]*\\((.*)\\) .. NULL)).*"
                        assignment = gensub(pattern, "\\1" , "g", $0)

                        #print "Assignment: " assignment

                        dest = gensub(/(.*) =.*/, "\\1" , "g", assignment)

                        print indentation assignment ";"
                        print prefix dest " " comparator " NULL)" suffix
                        next
                }
        }

        if ($0 ~ "((.* = .* .. NULL))") {
                assignment = gensub(/.*\(\((.*)) .. NULL).*/, "\\1" , "g", $0)
                prefix = gensub(/(.*if \().*/, "\\1", "g", $0)

                dest = gensub(/(.*) =.*/, "\\1" , "g", assignment)

                print indentation assignment ";"
                print prefix dest " " comparator " NULL)" suffix
                next
        }

        # No macro...
        print $0
}