Re: Losing character between SkipLine and ReadString from TextIO

[Gaius Mulley]

Rudolf Schubert <rudolf@muc.de> writes:

> Hi,
>
> I recently hit problems with my 'big squash program' when using SkipLine and
> ReadString from TextIO when reading text from files. 
>
> In the meantime I've done some first steps with 'cgdb' and could indeed see
> that there is a problem somewhere in the 'lower IO routines'. My knowledge
> does not suffice to point out exactly what's going wrong. Perhaps it has
> something to do with a missing doUnReadChar when 'switching' from SkipLine
> to ReadString? But I'm just guessing.
>
> My question would just be: could someone please have a look at my test program
> which I've included here? I'm creating a file with 2 lines of text in it.
> Then after having created the file I'm opening it again, calling SkipLine
> in order to jump to the second line. A ReadString should then read the second
> line but obviously the first character of the second line is missing from the
> output then.
>
>
> Here is my test program:
>
> (BTW is it ok to put the program here as text or should I better append it?)
>
> MODULE port_test6_gm2;
>
> FROM ChanConsts IMPORT
>   OpenResults, old, read, write;
> FROM IOChan IMPORT
>   ChanId;
> FROM StdChans IMPORT
>   StdOutChan;
> IMPORT StreamFile;
> FROM TextIO IMPORT
>   ReadString, SkipLine, WriteLn, WriteString;
>
>
> PROCEDURE SkipReadTest();
>   CONST
>     arr_len=                    128;
>
>   TYPE
>     arr_type=                   ARRAY[0..arr_len-1] OF CHAR;
>
>   VAR
>     cid_file:                   ChanId;
>     cid_out:                    ChanId;
>     file_name:                  arr_type;
>     a_str:                      arr_type;
>     res:                        OpenResults;
>
>   BEGIN                         (* PROCEDURE SkipReadTest *)
>     cid_out:=StdOutChan();
>
>     file_name:='test_data';
>
>     (* create file and write 2 lines to it *)
>     StreamFile.Open(cid_file, file_name, write+old, res);
>     IF res=opened THEN
>       WriteString(cid_file, '# line1');
>       WriteLn(cid_file);
>       WriteString(cid_file, '# line2');
>       WriteLn(cid_file);
>       StreamFile.Close(cid_file);
>     END;                        (* IF res=opened *)
>
>     (* (re-)open file and read from it *)
>     StreamFile.Open(cid_file, file_name, read, res);
>     IF res=opened THEN
>       SkipLine(cid_file);
>       ReadString(cid_file, a_str);
>       WriteString(cid_out, a_str);
>       WriteLn(cid_out);
>       StreamFile.Close(cid_file);
>     END;                        (* IF res=opened *)
>   END SkipReadTest;
>
>
> BEGIN                           (* MODULE port_test6_gm2 *)
>   SkipReadTest();
> END port_test6_gm2.
>
>
> BR
>
> Rudolf
>
> --
> Rudolf Schubert                 \
> Kirchstr. 18a                    \  mailto:rudolf@muc.de
> 82054 Sauerlach                   > http://www.dose.muc.de
> Deutschland                      /
> Tel. 08104/908311               /

Hi Rudolf,

thanks for the bug report and test code - I can also confirm the bug
exists and have filed a PR
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109779 and will fix it,

regards,
Gaius