Show error reason when compiler cannot write file

When the compiler fails to write an output file, it used to just print
"error writing file".  With this change, it also prints the error
reason:

    $ echo "-module(foo)." > foo.erl
    $ chmod -w .
    $ erlc foo.erl
    /tmp/bar/foo.bea#: error writing file: permission denied

1 files changed, 6 insertions, 4 deletions

diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index 82ff8a95f3..9fdfdadebf 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -236,6 +236,8 @@ format_error({epp,E}) ->
     epp:format_error(E);
 format_error(write_error) ->
     "error writing file";
+format_error({write_error, Error}) ->
+    io_lib:format("error writing file: ~ts", [file:format_error(Error)]);
 format_error({rename,From,To,Error}) ->
     io_lib:format("failed to rename ~ts to ~ts: ~ts",
 		  [From,To,file:format_error(Error)]);
@@ -1479,8 +1481,8 @@ save_binary_1(St) ->
 			 end,
 		    {error,St#compile{errors=St#compile.errors ++ Es}}
 	    end;
-	{error,_Error} ->
-	    Es = [{Tfile,[{none,compile,write_error}]}],
+	{error,Error} ->
+	    Es = [{Tfile,[{none,compile,{write_error,Error}}]}],
 	    {error,St#compile{errors=St#compile.errors ++ Es}}
     end.
 
@@ -1628,8 +1630,8 @@ listing(LFun, Ext, St) ->
 	    LFun(Lf, Code),
 	    ok = file:close(Lf),
 	    {ok,St};
-	{error,_Error} ->
-	    Es = [{Lfile,[{none,compile,write_error}]}],
+	{error,Error} ->
+	    Es = [{Lfile,[{none,compile,{write_error,Error}}]}],
 	    {error,St#compile{errors=St#compile.errors ++ Es}}
     end.