CPP: Resolve #endif FPs.

cpp/ql/src/Documentation/CommentedOutCode.qll

@@ -47,12 +47,27 @@ private predicate looksLikeCode(string line) {
   )
 }
 
+/**
+ * Holds if there is a preprocessor directive on the line indicated by
+ * `f` and `line`.
+ */
+private predicate preprocLine(File f, int line) {
+  exists(PreprocessorDirective pd, Location l |
+    pd.getLocation() = l and
+    l.getFile() = f and
+    l.getStartLine() = line
+  )
+}
+
 /**
  * The line of a C++-style comment within its file `f`.
  */
 private int lineInFile(CppStyleComment c, File f) {
   f = c.getFile() and
-  result = c.getLocation().getStartLine()
+  result = c.getLocation().getStartLine() and
+
+  // Ignore comments on the same line as a preprocessor directive.
+  not preprocLine(f, result)
 }
 
 /**
@@ -89,9 +104,17 @@ private int commentId(CppStyleComment c, File f, int line) {
  */
 class CommentBlock extends Comment {
   CommentBlock() {
-    this instanceof CppStyleComment
-    implies
-    not exists(CppStyleComment pred, File f | lineInFile(pred, f) + 1 = lineInFile(this, f))
+  	(
+      this instanceof CppStyleComment
+      implies
+      not exists(CppStyleComment pred, File f | lineInFile(pred, f) + 1 = lineInFile(this, f))
+    ) and (
+      // Ignore comments on the same line as a preprocessor directive.
+      not exists(Location l |
+        l = this.getLocation() and
+        preprocLine(l.getFile(), l.getStartLine())
+      )
+    )
   }
 
   /**