Emoji brings down hello-world example

[TamaMcGlinn]

If you put this program into the interactive hello-world compiler box, it apparently crashes. Changing the program again seems to still work, so I'm not sure this is really a problem.

with Ada.Text_IO; use Ada.Text_IO;

procedure Greet is
   Message : String (1 .. 4) := "😊";
   --        ^ Pre-defined array type.
   --          Component type is Character
begin
   for I in reverse Message'Range loop
      --    ^ Iterate in reverse order
      Put (Message (I));
   end loop;
   New_Line;
end Greet;

The error message is:

$ ./greet
The machine running the examples may not be available or is busy, please try again now or come back later.

[gusthoff]

This is an interesting corner case. Your example makes celery crash in the backend:

celery.backends.base.UnicodeDecodeError: ('Traceback (most recent call last):', '  File "/vagrant/app/widget/tasks.py", line 38, in run_program', '    code, out = project.run()', '  File "/vagrant/app/widget/project.py", line 307, in run', '    code, out, err = self.container.execute(line, reporter=rep)', '  File "/vagrant/app/widget/container.py", line 149, in execute', '    user)', '  File "/vagrant/app/widget/container.py", line 118, in _stream_exec', '    temp = stdout.decode("utf-8")', "UnicodeDecodeError: 'utf-8' codec can't decode byte 0x8a in position 0: invalid start byte", '')

The first issue with your code example is that you're using reverse in the loop, which invalidates the original UTF-8 string. This is indicated in the error message above.

However, even when removing the reverse keyword, the fact that you're calling Put for each character still makes celery crash:

celery.backends.base.UnicodeDecodeError: ('Traceback (most recent call last):', '  File "/vagrant/app/widget/tasks.py", line 38, in run_program', '    code, out = project.run()', '  File "/vagrant/app/widget/project.py", line 307, in run', '    code, out, err = self.container.execute(line, reporter=rep)', '  File "/vagrant/app/widget/container.py", line 149, in execute', '    user)', '  File "/vagrant/app/widget/container.py", line 118, in _stream_exec', '    temp = stdout.decode("utf-8")', "UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf0 in position 0: unexpected end of data", '')

In this case, celery most probably processes each character as a separate string. Of course, such a string would be incomplete, as it doesn't have a complete sequence in UTF-8 format. This is what might be causing the error message above.

[gusthoff]

Note that the correct version of the code example works fine:

with Ada.Text_IO;              use Ada.Text_IO;
with Ada.Strings.UTF_Encoding; use Ada.Strings.UTF_Encoding;

procedure Greet is
   Message : constant UTF_8_String := "😊";
begin
   Put_Line (Message);
end Greet;

Also, if you assume that all strings are in UTF-8 format and don't need to be processed, you could just write this instead:

with Ada.Text_IO; use Ada.Text_IO;

procedure Greet is
   Message : constant String := "😊";
begin
   Put_Line (Message);
end Greet;