Don't crash when a cg cannot be loaded.

Summary:
public This assert false causes the whole analysis to crash.
It is currently happening intermittently which makes it hard to debug.
Other inconsistencies don't cause the whole analysis to crash normally,
so this one seems to be too strict.

Reviewed By: cristianoc

Differential Revision: D2849864

fb-gh-sync-id: de6dce0

infer/src/backend/exe_env.ml

@@ -85,29 +85,32 @@ let add_active_proc exe_env proc_name =
 (** like add_cg, but use exclude_fun to determine files to be excluded *)
 let add_cg_exclude_fun (exe_env: t) (source_dir : DB.source_dir) exclude_fun =
   let cg_fname = DB.source_dir_get_internal_file source_dir ".cg" in
-  let cg = match Cg.load_from_file cg_fname with
-    | None -> (L.err "cannot load %s@." (DB.filename_to_string cg_fname); assert false)
+  let cg_opt = match Cg.load_from_file cg_fname with
+    | None -> (L.stderr "cannot load %s@." (DB.filename_to_string cg_fname); None)
     | Some cg ->
         Cg.restrict_defined cg exe_env.active_opt;
-        cg in
-  let source = Cg.get_source cg in
-  if exclude_fun source then None
-  else
-    let nLOC = Cg.get_nLOC cg in
-    Cg.extend exe_env.cg cg;
-    let file_data = new_file_data source nLOC cg_fname in
-    let defined_procs = Cg.get_defined_nodes cg in
-    IList.iter (fun pname ->
-        let should_update =
-          if Procname.Hash.mem exe_env.proc_map pname then
-            let old_source = (Procname.Hash.find exe_env.proc_map pname).source in
-            exe_env.procs_defined_in_several_files <- Procname.Set.add pname exe_env.procs_defined_in_several_files;
-            (* L.err "Warning: procedure %a is defined in both %s and %s@." Procname.pp pname (DB.source_file_to_string source) (DB.source_file_to_string old_source); *)
-            source < old_source (* when a procedure is defined in several files, map to the first alphabetically *)
-          else true in
-        if should_update then Procname.Hash.replace exe_env.proc_map pname file_data) defined_procs;
-    Hashtbl.add exe_env.file_map source file_data;
-    Some cg
+        Some cg in
+  match cg_opt with
+  | None -> None
+  | Some cg ->
+      let source = Cg.get_source cg in
+      if exclude_fun source then None
+      else
+        let nLOC = Cg.get_nLOC cg in
+        Cg.extend exe_env.cg cg;
+        let file_data = new_file_data source nLOC cg_fname in
+        let defined_procs = Cg.get_defined_nodes cg in
+        IList.iter (fun pname ->
+            let should_update =
+              if Procname.Hash.mem exe_env.proc_map pname then
+                let old_source = (Procname.Hash.find exe_env.proc_map pname).source in
+                exe_env.procs_defined_in_several_files <- Procname.Set.add pname exe_env.procs_defined_in_several_files;
+                (* L.err "Warning: procedure %a is defined in both %s and %s@." Procname.pp pname (DB.source_file_to_string source) (DB.source_file_to_string old_source); *)
+                source < old_source (* when a procedure is defined in several files, map to the first alphabetically *)
+              else true in
+            if should_update then Procname.Hash.replace exe_env.proc_map pname file_data) defined_procs;
+        Hashtbl.add exe_env.file_map source file_data;
+        Some cg
 
 (** add call graph from fname in the spec db, with relative tenv and cfg, to the execution environment *)
 let add_cg exe_env (source_dir : DB.source_dir) =