From e5009cd41d1fadda741c5e56809c440be4fa66cd Mon Sep 17 00:00:00 2001
From: Troels Henriksen <athas@sigkill.dk>
Date: Sat, 19 Jun 2021 15:59:15 +0200
Subject: [PATCH] Add Posix.IO.dup2, as specified by Basis Library.

---
 basis/POSIX_IO.sml  | 1 +
 basis/Posix.sml     | 4 ++++
 src/Runtime/Posix.c | 6 ++++++
 3 files changed, 11 insertions(+)

diff --git a/basis/POSIX_IO.sml b/basis/POSIX_IO.sml
index f72384417..4a1fa0889 100644
--- a/basis/POSIX_IO.sml
+++ b/basis/POSIX_IO.sml
@@ -24,6 +24,7 @@ signature POSIX_IO =
 
     val close : file_desc -> unit
     val dup : file_desc -> file_desc
+    val dup2 : {old : file_desc, new : file_desc} -> unit
     val dupfd : {old : file_desc, base : file_desc} -> file_desc
     val pipe : unit -> {infd : file_desc, outfd : file_desc}
    
diff --git a/basis/Posix.sml b/basis/Posix.sml
index f97616559..198fe5656 100644
--- a/basis/Posix.sml
+++ b/basis/Posix.sml
@@ -823,6 +823,10 @@ struct
 
     fun dup f = dupfd {old = f, base = 0}
 
+    fun dup2 {old, new} = let val a = prim ("@sml_dup2", (old : int, new : int)) : int
+                          in if a = ~1 then raiseSys "dup2" NONE "" else ()
+                          end
+
     fun lseek (fd, p, w) =
         let
           val k = case w of SEEK_SET => 0
diff --git a/src/Runtime/Posix.c b/src/Runtime/Posix.c
index fc58a27a2..f07ffb797 100644
--- a/src/Runtime/Posix.c
+++ b/src/Runtime/Posix.c
@@ -302,6 +302,12 @@ sml_dupfd(size_t f, size_t arg)
   return (size_t) fcntl((int) f, F_DUPFD, (long) arg);
 }
 
+size_t
+sml_dup2(size_t f, size_t t)
+{
+  return (size_t) dup2((int) f, (int) t);
+}
+
 uintptr_t
 sml_getStdNumbers(uintptr_t triple)
 {