[extlib] add recursive mkdir function (fixes #425)

src/kernel_services/plugin_entry_points/plugin.ml

@@ -325,7 +325,7 @@ struct
 
     let mk_dir d =
       try
-        Unix.mkdir d 0o755;
+        Extlib.mkdir ~parents:true d 0o755;
         L.warning "creating %s directory `%s'" O.option_name d;
         d
       with Unix.Unix_error _ -> 

src/libraries/stdlib/extlib.ml

@@ -343,6 +343,18 @@ let try_finally ~finally f x =
   hence interrupting the process, might not work: child processes still need to
   run some daemons, such as [flush_all] which is registered by default. *)
 
+let rec mkdir ?(parents=false) name perm =
+  try Unix.mkdir name perm
+  with
+  | Unix.Unix_error (Unix.ENOENT,_,_) when parents ->
+    let parent_name = Filename.dirname name in
+    if name <> parent_name then
+      begin
+        mkdir ~parents parent_name perm;
+        Unix.mkdir name perm
+      end
+  | e -> raise e
+
 let pid = Unix.getpid ()
 let safe_at_exit f =
   at_exit

src/libraries/stdlib/extlib.mli

@@ -331,6 +331,17 @@ val try_finally: finally:(unit -> unit) -> ('a -> 'b) -> 'a -> 'b
 (** System commands *)
 (* ************************************************************************* *)
 
+val mkdir : ?parents:bool -> string -> Unix.file_perm -> unit
+  (** [mkdir ?parents name perm] creates directory [name] with permission
+      [perm]. If [parents] is true, recursively create parent directories
+      if needed. [parents] defaults to false.
+      Note that this function may create some of the parent directories
+      and then fail to create the children, e.g. if [perm] does not allow
+      user execution of the created directory. This will leave the filesystem
+      in a modified state before raising an exception.
+      @raise [Unix.Unix_error] if cannot create [name] or its parents.
+      @since Frama-C+dev  *)
+
 val safe_at_exit : (unit -> unit) -> unit
   (** Register function to call with [Pervasives.at_exit], but only
       for non-child process (fork). The order of execution is preserved