For these two simple programs:
with Ada.Text_IO; use Ada.Text_IO; procedure Hello is begin Put("Hello"); Put(" "); Put("World!"); end Hello;
with Ada.Text_IO; use Ada.Text_IO; with Ada.Text_IO.Text_Streams; use Ada.Text_IO.Text_Streams; procedure hello_stream is std_out : Stream_Access; begin std_out := Stream (Standard_Output); String'Write (std_out, "Hello"); String'Write (std_out, " "); String'Write (std_out, "World!"); end hello_stream;
When executing the two program, you would have two different result, for hello program:
# ./hello Hello World! #
For hello_stream program:
# ./hello_stream Hello World!#
I have known this problem for some time, but did not dig into the root cause of it. Recently I asked this question in comp.lang.ada group for a root cause of it. And Jeffrey gave me the answer.
For gnat compiler File_Type is defined at a-textio.ads:
... type Text_AFCB; type File_Type is access all Text_AFCB; type Text_AFCB is new FCB.AFCB with record ... end record ... procedure AFCB_Close (File : not null access Text_AFCB);Where FCB.AFCB is a tagged type defined in s-ficobl.ads. In AFCB_Close() procedure, it calls Terminate_Line(), which will try to insert a new line if not terminate properly.
It seems, when program exit, gnat doing the finalization for Standard_Output call AFCB_Close(), which insert the new line if necessary.
p.s. This is tested under Slackware64 Linux with GCC gnat compiler.