Allow escripts with only two lines

The current implementation assumes that escripts all have at least
three lines. But according to the escript documentation, comments
on the second line and emulator flags on the third line are all
optional. Thus escripts with only two lines -- shebang on the
first line and code on the second line -- will not run. This commit
fixes the problem by rearranging the escript header parsing logic,
and recognize the escript body on the second line if the header only
contains a line of shebang.

3 files changed, 59 insertions, 41 deletions

diff --git a/lib/stdlib/src/escript.erl b/lib/stdlib/src/escript.erl
index 7f5ef4df42..c42ae981e7 100644
--- a/lib/stdlib/src/escript.erl
+++ b/lib/stdlib/src/escript.erl
@@ -481,46 +481,49 @@ find_first_body_line(Fd, HeaderSz0, LineNo, KeepFirst, Sections) ->
     %% Look for special comment on second line
     Line2 = get_line(Fd),
     {ok, HeaderSz2} = file:position(Fd, cur),
-    case classify_line(Line2) of
-	emu_args ->
-	    %% Skip special comment on second line
-	    Line3 = get_line(Fd),
-	    {HeaderSz2, LineNo + 2, Fd,
-	     Sections#sections{type = guess_type(Line3),
-			       comment = undefined,
-			       emu_args = Line2}};
-	Line2Type ->
-	    %% Look for special comment on third line
-	    Line3 = get_line(Fd),
-	    {ok, HeaderSz3} = file:position(Fd, cur),
-	    Line3Type = classify_line(Line3),
-	    if
-		Line3Type =:= emu_args ->
-		    %% Skip special comment on third line
-		    Line4 = get_line(Fd),
-		    {HeaderSz3, LineNo + 3, Fd,
-		     Sections#sections{type = guess_type(Line4),
-				       comment = Line2,
-				       emu_args = Line3}};
-		Sections#sections.shebang =:= undefined,
-		KeepFirst =:= true ->
-		    %% No shebang. Use the entire file
-		    {HeaderSz0, LineNo, Fd,
-		     Sections#sections{type = guess_type(Line2)}};
-		Sections#sections.shebang =:= undefined ->
-		    %% No shebang. Skip the first line
-		    {HeaderSz1, LineNo, Fd,
-		     Sections#sections{type = guess_type(Line2)}};
-		Line2Type =:= comment ->
-		    %% Skip shebang on first line and comment on second
-		    {HeaderSz2, LineNo + 2, Fd,
-		     Sections#sections{type = guess_type(Line3),
-				       comment = Line2}};
-		true ->
-		    %% Just skip shebang on first line
-		    {HeaderSz1, LineNo + 1, Fd,
-		     Sections#sections{type = guess_type(Line2)}}
-	    end
+    if
+        Sections#sections.shebang =:= undefined,
+        KeepFirst =:= true ->
+            %% No shebang. Use the entire file
+            {HeaderSz0, LineNo, Fd,
+             Sections#sections{type = guess_type(Line2)}};
+        Sections#sections.shebang =:= undefined ->
+            %% No shebang. Skip the first line
+            {HeaderSz1, LineNo, Fd,
+             Sections#sections{type = guess_type(Line2)}};
+        true ->
+            case classify_line(Line2) of
+                emu_args ->
+                    %% Skip special comment on second line
+                    Line3 = get_line(Fd),
+                    {HeaderSz2, LineNo + 2, Fd,
+                     Sections#sections{type = guess_type(Line3),
+                                       comment = undefined,
+                                       emu_args = Line2}};
+                comment ->
+                    %% Look for special comment on third line
+                    Line3 = get_line(Fd),
+                    {ok, HeaderSz3} = file:position(Fd, cur),
+                    Line3Type = classify_line(Line3),
+                    if
+                        Line3Type =:= emu_args ->
+                            %% Skip special comment on third line
+                            Line4 = get_line(Fd),
+                            {HeaderSz3, LineNo + 3, Fd,
+                             Sections#sections{type = guess_type(Line4),
+                                               comment = Line2,
+                                               emu_args = Line3}};
+                        true ->
+                            %% Skip shebang on first line and comment on second
+                            {HeaderSz2, LineNo + 2, Fd,
+                             Sections#sections{type = guess_type(Line3),
+                                               comment = Line2}}
+                    end;
+                _ ->
+                    %% Just skip shebang on first line
+                    {HeaderSz1, LineNo + 1, Fd,
+                     Sections#sections{type = guess_type(Line2)}}
+            end
     end.
 
 classify_line(Line) ->
diff --git a/lib/stdlib/test/escript_SUITE.erl b/lib/stdlib/test/escript_SUITE.erl
index 28d69232a0..0b9106a99c 100644
--- a/lib/stdlib/test/escript_SUITE.erl
+++ b/lib/stdlib/test/escript_SUITE.erl
@@ -28,6 +28,7 @@
 	 strange_name/1,
 	 emulator_flags/1,
 	 emulator_flags_no_shebang/1,
+	 two_lines/1,
 	 module_script/1,
 	 beam_script/1,
 	 archive_script/1,
@@ -49,7 +50,7 @@ suite() ->
 
 all() -> 
     [basic, errors, strange_name, emulator_flags,
-     emulator_flags_no_shebang,
+     emulator_flags_no_shebang, two_lines,
      module_script, beam_script, archive_script, epp,
      create_and_extract, foldl, overflow,
      archive_script_file_access, unicode].
@@ -153,6 +154,18 @@ emulator_flags(Config) when is_list(Config) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+two_lines(Config) when is_list(Config) ->
+    Data = proplists:get_value(data_dir, Config),
+    Dir = filename:absname(Data),		%Get rid of trailing slash.
+    run(Dir, "two_lines -arg1 arg2 arg3",
+	[<<"main:[\"-arg1\",\"arg2\",\"arg3\"]\n"
+	   "ERL_FLAGS=false\n"
+	   "unknown:[]\n"
+	   "ExitCode:0">>]),
+    ok.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 emulator_flags_no_shebang(Config) when is_list(Config) ->
     Data = proplists:get_value(data_dir, Config),
     Dir = filename:absname(Data),		%Get rid of trailing slash.
diff --git a/lib/stdlib/test/escript_SUITE_data/two_lines b/lib/stdlib/test/escript_SUITE_data/two_lines
new file mode 100755
index 0000000000..cf4e99639c
--- /dev/null
+++ b/lib/stdlib/test/escript_SUITE_data/two_lines
@@ -0,0 +1,2 @@
+#! /usr/bin/env escript
+main(MainArgs) -> io:format("main:~p\n", [MainArgs]), ErlArgs = init:get_arguments(), io:format("ERL_FLAGS=~p\n", [os:getenv("ERL_FLAGS")]), io:format("unknown:~p\n",[[E || E <- ErlArgs, element(1, E) =:= unknown]]).