C++: Add FailedExtractions.ql

cpp/ql/src/Diagnostics/FailedExtractions.ql

@@ -0,0 +1,22 @@
+/**
+ * @kind diagnostic
+ * @id cpp/diagnostics/failed-extractions
+ */
+import cpp
+
+class AnonymousCompilation extends Compilation {
+  override string toString() {
+    result = "<compilation>"
+  }
+}
+
+string describe(Compilation c) {
+  if c.getArgument(1) = "--mimic"
+  then result = "compiler invocation " + concat(int i | i > 1 | c.getArgument(i), " " order by i)
+  else result = "extractor invocation " + concat(int i | | c.getArgument(i), " " order by i)
+}
+
+from Compilation c
+where not c.normalTermination()
+select c, "Extraction failed for " + describe(c), 2
+