src/Pure/General/sha1.ML

 (* C library and memory *)
 
 val library_path =
   Path.explode ("$ML_HOME/" ^ (if ML_System.platform_is_windows then "sha1.dll" else "libsha1.so"));
 
-val library_call =
+fun build_call () =
   Foreign.buildCall3
     (Foreign.getSymbol (Foreign.loadLibrary (File.platform_path library_path)) "sha1_buffer",
       (Foreign.cByteArray, Foreign.cUlong, Foreign.cPointer), Foreign.cPointer);
+
+val library_call =
+  if ML_System.platform_is_arm then fn args => build_call () args else build_call ();
 
 fun with_memory n =
   Thread_Attributes.uninterruptible (fn restore_attributes => fn f =>
     let
       val mem = Foreign.Memory.malloc (Word.fromInt n);