PR9931: generate log to help diagnosing occasional cache hash collisions

Ideas from Frank Ch. Eigler:
- extending the hash.add() function to pass names along with the
  hash-mix values, so that class hash can internally track the
  hash-report string
- storing the reports themselves in the cache, beside the .ko / .c
  files, and changing the cache-size-limit logic to delete
  these .txt files upon garbage collection

* hash.h : New member parm_stream.
* hash.cxx (get_parms): New function to convert parms stream to string.
  (hash::add): Aggregrate parms stream.
  (create_hash_log): New function to log hash operation.
  (find_*_hash): Log hash at the end of function.
* cache.cxx (clean_cache): Remove log when cache reaches limitation.

1 files changed, 5 insertions, 0 deletions

diff --git a/hash.h b/hash.h
index 6bb1c78a..173f8e51 100644
--- a/hash.h
+++ b/hash.h
@@ -1,5 +1,7 @@
 #include <string>
 #include <vector>
+#include <sstream>
+#include <fstream>
 
 extern "C" {
 #include <string.h>
@@ -13,9 +15,11 @@ class hash
 {
 private:
   struct mdfour md4;
+  std::ostringstream parm_stream;
 
 public:
   hash() { start(); }
+  hash(const hash &base) { start(); parm_stream << base.parm_stream.str();}
 
   void start();
 
@@ -34,6 +38,7 @@ public:
   void add_file(const std::string& filename);
 
   void result(std::string& r);
+  std::string get_parms();
 };
 
 void find_hash (systemtap_session& s, const std::string& script);