[pulse] Add unreachable point to the trace of memory leaks

Summary: When looking at some reports I realised that adding the place where the memory becomes unreachable to the trace makes it more readable.

Reviewed By: skcho

Differential Revision: D20790277

fbshipit-source-id: d5df69e68

infer/src/pulse/PulseDiagnostic.ml

@@ -110,13 +110,13 @@ let get_trace = function
            ~pp_immediate:(fun fmt -> F.pp_print_string fmt "invalid access occurs here")
            access_trace
       @@ []
-  | MemoryLeak {allocation_trace} ->
+  | MemoryLeak {location; allocation_trace} ->
       let access_start_location = Trace.get_start_location allocation_trace in
       add_errlog_header ~title:"allocation part of the trace starts here" access_start_location
       @@ Trace.add_to_errlog ~nesting:0
            ~pp_immediate:(fun fmt -> F.pp_print_string fmt "allocation occurs here")
            allocation_trace
-      @@ []
+      @@ [Errlog.make_trace_element 0 location "memory becomes unreachable here" []]
   | StackVariableAddressEscape {history; location; _} ->
       ValueHistory.add_to_errlog ~nesting:0 history
       @@

infer/tests/codetoanalyze/c/pulse/issues.exp

@@ -1,3 +1,3 @@
-codetoanalyze/c/pulse/memory_leak.c, malloc_interproc_no_free_bad, 0, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,when calling `create_p` here,allocation occurs here]
+codetoanalyze/c/pulse/memory_leak.c, malloc_interproc_no_free_bad, 0, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,when calling `create_p` here,allocation occurs here,memory becomes unreachable here]
-codetoanalyze/c/pulse/memory_leak.c, malloc_interproc_no_free_bad2, 4, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,allocation occurs here]
+codetoanalyze/c/pulse/memory_leak.c, malloc_interproc_no_free_bad2, 4, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,allocation occurs here,memory becomes unreachable here]
-codetoanalyze/c/pulse/memory_leak.c, malloc_no_free_bad, 0, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,allocation occurs here]
+codetoanalyze/c/pulse/memory_leak.c, malloc_no_free_bad, 0, PULSE_MEMORY_LEAK, no_bucket, ERROR, [allocation part of the trace starts here,allocation occurs here,memory becomes unreachable here]