investigation: Segfault in GDB (IV) (related to #946)

now isolated the problem.
It is triggered by a std::function bound to a lambda
where some argument type is picked up from the
template parameter of the enclosing function.

research/crash_gdb_jessie-2015-08.sh

@@ -0,0 +1,51 @@
+#/!bin/sh
+#
+# crash_gdb -- demostrate a Segfault when invoking the debugger
+#              observed 8/2015 on Debian/Jessie on X86_64
+#              <deb@ichthyostega.de>
+
+CODE=`mktemp`
+
+cat << __END__ | g++ -x c++ - -o$CODE -std=gnu++11  && echo "compiled successfully to $CODE"
+
+#include <functional>
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cout;
+using std::endl;
+
+
+template<class ELM>
+inline string
+activate (ELM& something)
+  {
+    std::function<string(ELM const&)> lambda = [] (ELM const& val)
+                                                  {
+                                                    return string(val);
+                                                  };
+    return lambda(something);
+  }
+
+
+int
+main (int, char**)
+  {
+    cout << activate ("Data") << endl;
+    return 0;
+  }
+
+__END__
+
+
+$CODE && echo "executed successfully without debugger"
+
+echo -e "now try to crash the debugger...\n\n"
+
+gdb $CODE -ex run -ex quit
+
+if (($?))
+	then echo -e "\n\n\n\n *** Debugger crashed"
+	else echo -e "\n\n\n\n +++ Debugger worked, no crash"
+fi

research/try.cpp

@@ -31,81 +31,40 @@
 
 
 /** @file try.cpp
- ** Investigation: Segfault when loading into GDB (on Debian/Jessie 64bit)
+ ** Investigation: Segfault when loading into GDB (on Debian/Jessie 64bit).
+ ** 
+ ** Problem could be narrowed down to a std::function bound to lambda,
+ ** where some argument type is picked up as template parameter
  **
  */
 
-#include "lib/test/test-helper.hpp"
+#include <functional>
-//#include "lib/format-util.hpp"
-#include "lib/meta/trait.hpp"
-#include "lib/itertools.hpp"
-#include "lib/symbol.hpp"
-
 #include <iostream>
 #include <string>
-#include <vector>
 
 using std::string;
-using std::vector;
 using std::cout;
 using std::endl;
 
 
-  namespace { // helper to build range iterator on demand
-    template<class CON, typename TOGGLE = void>
-    struct _RangeIter
-      {
-        using StlIter = typename CON::const_iterator;
-        
-        lib::RangeIter<StlIter> iter;
-        
-        _RangeIter(CON const& collection)
-          : iter(begin(collection), end(collection))
-          { }
-      };
-    
-  }
 
-
+template<class ELM>
-template<class CON>
 inline string
-join (CON&& coll, string const& delim =", ")
+activate (ELM& something)
-{
+  {
-  using Coll = typename lib::meta::Strip<CON>::Type;
+    std::function<string(ELM const&)> lambda = [] (ELM const& val)
-  using Val =  typename Coll::value_type;
+                                                  {
-  
+                                                    return string(val);
-  std::function<string(Val const&)> toString = [] (Val const& val) { return string(val); };
+                                                  };
-  
+    return lambda(something);
-  _RangeIter<Coll> range(std::forward<Coll>(coll));
+  }
-  auto strings = lib::transformIterator(range.iter, toString);
-  
-  if (!strings) return "";
-  
-  std::ostringstream buffer;
-  for (string const& elm : strings)
-      buffer << elm << delim;
-  
-  // chop off last delimiter
-  size_t len = buffer.str().length();
-  ASSERT (len > delim.length());
-  return buffer.str().substr(0, len - delim.length());
-}
 
 
 
 int
 main (int, char**)
   {
-    vector<string> crew;
+    cout << activate("Data") << endl;
-    crew.push_back("Picard");
-    crew.push_back("Riker");
-    crew.push_back("Data");
-    crew.push_back("Troi");
-    crew.push_back("Worf");
-    crew.push_back("Crusher");
-    crew.push_back("La Forge");
-    
-    cout << "enterprise = " << join(crew)<<endl;
     
     cout <<  "\n.gulp.\n";