[Bug ada/66390] New: Text_IO.Get_Line does not correctly handle missing line marker for last line in all cases

[tornenvi at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66390

            Bug ID: 66390
           Summary: Text_IO.Get_Line does not correctly handle missing
                    line marker for last line in all cases
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tornenvi at gmail dot com
  Target Milestone: ---

Created attachment 35685
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35685&action=edit
Program file

For a "non canonical" file as described in the reference manual
   gcc\ada\doc\gnat_rm\the_implementation_of_standard_i_o.html#text-io 
  which has no line marker at the end of file, then it is possible for 
  Get_Line to return the incorrect length.

  Note that a "non canonical" file is a "standard" file in windows so this
  use case is common.

  The program file attached FileRead.adb simply reads the first line of a
  text file into a 6 character buffer, and outputs the length of the line
  read, the line and the line again as hex.

  I compile FileRead.adb with

    gnatmake FileRead.adb

  I use windows notepad to create the test file Test.txt. note that
  windows notepad will not place a end of line marker at the end of 
  the file.


  When using Test.txt with the one line of text
   ABCD
  with no blank line at the end of the file I get output 1 below

-- Output 1 ------------------------------------------------------
Length=  4
Line=[ABCDXX]
Line as hex=[414243445858]
------------------------------------------------------------------

  as expected. However if Test.txt is the one line of text
   ABCDE
  with no blank line at the end of the file then I get output 2 below

-- Output 2 -----------------------------------------------------
Length=  6
Line=[ABCDE ]
Line as hex=[4142434445ff]
-----------------------------------------------------------------

  I receive an unexpected length of 6, expected 5. The fact that the last two
  characters are not 'XX' is acceptable since ARM A.10.7 19 says
  "The values of characters not assigned are not specified."

  I get the same output 2 if I compile the program with
  GNAT GPL 2014, 2013,2012 or 2011 or with mingw FSF GNAT 4.7.0-1 or 4.8.1-4.

  However if I compile with mingw FSF GNAT 4.5.2-1 , 4.5.0-1, 4.4.0 or
  3.4.5 then I get the expected output 3 below

-- Output 3 -----------------------------------------------------
Length=  5
Line=[ABCDEX]
Line as hex=[414243444558]
-----------------------------------------------------------------

  Under windows the one line text file does not have an end of line
  character (usually CRLF) which means it is not a canonical text file
  as described here

  gcc\ada\doc\gnat_rm\the_implementation_of_standard_i_o.html#text-io 

  however that section also states that text_io can be use to read non 
  canonical text files and the very last line of that section says
    "Every LF character is considered to end a line, and there is an
    implied LF character at the end of the file."

  this indicates to me that there should be an implied LF at the end of the
  file and I should be getting the expected output 3 result for
  all the compilers. 

  The program works correctly for test.txt with 4 and less or 6 and more
  characters.


  I believe the problem is in 

    \gcc\ada\a-tigeli.adb

  at line 187 a comment says

    --  If we get EOF after already reading data, this is an incomplete
    --  last line, in which case no End_Error should be raised.

  however at line 193 there is no test to 
  check that the last character read 'ch' is the EOF marker instead
  it adds it the Item buffer and increments the length.

  I suggest line 193 be changed from 

      elsif ch /= LM then
  to 
      elsif ch /= LM and ch /= EOF then