[sqlite] symlink too-long db paths for db_open

Summary:
Add more defence for too long database paths: when creating a database and when opening an existing one.

Also fix bug where `Filename.temp_file` creates empty file and symlink creation fails.

Reviewed By: dulmarod

Differential Revision:
D66536892

Privacy Context Container: L1208441

fbshipit-source-id: 1d4031d7577299e175431018caa9beb3bfc36031

infer/src/base/Database.ml

@@ -138,14 +138,31 @@ type location = Primary | Secondary of string [@@deriving show {with_path= false
 let results_dir_get_path entry = ResultsDirEntryName.get_path ~results_dir:Config.results_dir entry
 
 let get_db_path location id =
-  match location with Primary -> results_dir_get_path (get_db_entry id) | Secondary file -> file
+  match location with
+  | Secondary file ->
+      file
+  | Primary ->
+      let path_to_db = results_dir_get_path (get_db_entry id) in
+      if String.length path_to_db > SqliteUtils.sqlite_max_path_length then (
+        let link_name = Filename.temp_file "infer-merge-sqlite-trampoline" ".db" in
+        Unix.unlink link_name ;
+        Unix.symlink ~target:(Filename.dirname path_to_db) ~link_name ;
+        Filename.concat link_name (Filename.basename path_to_db) )
+      else path_to_db
 
 
 let create_db location id =
   let final_db_path = get_db_path location id in
   let pid = Unix.getpid () in
+  let in_dir =
+    (* if the length of the path to the results directory is greater than Sqlite's limit
+       then create the DB in [$TMPDIR] otherwise in [results_dir/tmp] *)
+    let results_temp_dir = results_dir_get_path Temporary in
+    if String.length results_temp_dir > SqliteUtils.sqlite_max_path_length - 50 then None
+    else Some results_temp_dir
+  in
   let temp_db_path =
-    Filename.temp_file ~in_dir:(results_dir_get_path Temporary)
+    Filename.temp_file ?in_dir
       ( match id with
       | CaptureDatabase ->
           "capture." ^ Pid.to_string pid ^ ".db"

infer/src/base/SqliteUtils.ml

@@ -103,9 +103,10 @@ let with_attached_db ~db_file ~db_name ?(immutable = false) ~f db =
     then (db_file, false)
     else
       let in_dir = ResultsDirEntryName.get_path ~results_dir:Config.results_dir Temporary in
-      let link_name = Filename.temp_file ~in_dir "infer-merge-sqlite-trampoline" "db" in
-      Unix.symlink ~target:db_file ~link_name ;
-      (link_name, true)
+      let link_name = Filename.temp_file ~in_dir "infer-merge-sqlite-trampoline-out" "" in
+      Unix.unlink link_name ;
+      Unix.symlink ~target:(Filename.dirname db_file) ~link_name ;
+      (Filename.concat link_name (Filename.basename db_file), true)
   in
   let attach_stmt =
     Printf.sprintf "ATTACH '%s%s%s' AS %s"

infer/src/base/SqliteUtils.mli

@@ -14,6 +14,9 @@ exception Error of string
 (** Raised from serializers when final size exceeds Sqlite3 limits (normally 1000_000_000 bytes). *)
 exception DataTooBig
 
+val sqlite_max_path_length : int
+(** an underapproximation of the maximum path length allowed in sqlite *)
+
 val check_result_code : Sqlite3.db -> log:string -> Sqlite3.Rc.t -> unit
 (** Assert that the result is either [Sqlite3.Rc.OK] or [Sqlite3.Rc.ROW]. If the result is not
     valid, raise {!Error}. *)