Merge pull request #5385 from github/igfoo/failed_extractions

C++: Add FailedExtractions.ql

cpp/change-notes/2021-03-11-failed-extractions.md

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+codescanning
+* Added cpp/diagnostics/failed-extractions. This query gives information about which extractions did not run to completion.

cpp/ql/src/Diagnostics/FailedExtractions.ql

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+/**
+ * @name Failed extractions
+ * @description Gives the command-line of compilations for which extraction did not run to completion.
+ * @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