WIP for ERANGE handling

wip.diff

diff --git a/src/unix/lwt_unix.cppo.ml b/src/unix/lwt_unix.cppo.ml
index 89bb84228..69ef1a45d 100644
--- a/src/unix/lwt_unix.cppo.ml
+++ b/src/unix/lwt_unix.cppo.ml
@@ -1543,29 +1543,48 @@ let getpwnam name =
   else
     run_job (getpwnam_job name)
 
-external getgrnam_job : string -> Unix.group_entry job = "lwt_unix_getgrnam_job"
+let retry_after_erange name trying =
+  let rec loop factor =
+     try
+       trying factor
+     with
+        | Unix.Unix_error(Unix.ERANGE, namename, _) -> begin
+          assert (name = namename);
+          loop (factor * 2)
+        end
+    in
+    loop 1
+
+
+external getgrnam_job : (string * int) -> Unix.group_entry job = "lwt_unix_getgrnam_job"
 
 let getgrnam name =
   if Sys.win32 || Lwt_config.android then
     Lwt.return (Unix.getgrnam name)
   else
-    run_job (getgrnam_job name)
+    retry_after_erange "getgrnam" (fun factor ->
+        run_job (getgrnam_job (name, factor))
+      )
 
-external getpwuid_job : int -> Unix.passwd_entry job = "lwt_unix_getpwuid_job"
+external getpwuid_job : (int * int) -> Unix.passwd_entry job = "lwt_unix_getpwuid_job"
 
 let getpwuid uid =
   if Sys.win32 || Lwt_config.android then
     Lwt.return (Unix.getpwuid uid)
   else
-    run_job (getpwuid_job uid)
+    retry_after_erange "getpwuid" (fun factor ->
+          run_job (getpwuid_job (uid, factor))
+      )
 
-external getgrgid_job : int -> Unix.group_entry job = "lwt_unix_getgrgid_job"
+external getgrgid_job : (int * int) -> Unix.group_entry job = "lwt_unix_getgrgid_job"
 
 let getgrgid gid =
   if Sys.win32 || Lwt_config.android then
     Lwt.return (Unix.getgrgid gid)
   else
-    run_job (getgrgid_job gid)
+    retry_after_erange "getgrnam" (fun factor ->
+        run_job (getgrgid_job (gid, factor))
+      )
 
 (* +-----------------------------------------------------------------+
    | Sockets                                                         |
diff --git a/src/unix/unix_c/unix_get_pw_gr_nam_id_job.c b/src/unix/unix_c/unix_get_pw_gr_nam_id_job.c
index e256a2963..d4cd0364f 100644
--- a/src/unix/unix_c/unix_get_pw_gr_nam_id_job.c
+++ b/src/unix/unix_c/unix_get_pw_gr_nam_id_job.c
@@ -16,7 +16,6 @@
 #include <pwd.h>
 #include <sys/types.h>
 #include <unistd.h>
-#include <errno.h>
 
 #include "lwt_unix.h"
 
@@ -78,21 +77,14 @@ static value alloc_group_entry(struct group *entry)
         ARG_DECL;                                                      \
     };                                                                 \
                                                                        \
-    static void worker_##FUNC(struct job_##FUNC *job)                  \
+    static void worker_##FUNC(struct job_##FUNC *job, int factor)      \
     {                                                                  \
         size_t buffer_size = sysconf(_SC_##CONF##_R_SIZE_MAX);         \
         if (buffer_size == (size_t)-1) buffer_size = 16384;            \
+        buffer_size = buffer_size * factor;                            \
         job->buffer = (char *)lwt_unix_malloc(buffer_size);            \
         job->result = FUNC##_r(job->ARG, &job->entry, job->buffer,     \
                                buffer_size, &job->ptr);                \
-        if (job->result == -1) {                                       \
-            if (errno == ERANGE) {                                         \
-                buffer_size = buffer_size *2;                              \
-                job->buffer = (char *)lwt_unix_malloc(buffer_size);        \
-                job->result = FUNC##_r(job->ARG, &job->entry, job->buffer, \
-                                       buffer_size, &job->ptr);            \
-            }                                                              \
-        }                                                              \
     }                                                                  \
                                                                        \
     static value result_##FUNC(struct job_##FUNC *job)                 \