[Bug libfortran/56737] [4.6/4.7/4.8/4.9 Regression] Wrong I/O result with format cache for Hollerith strings

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56737

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |burnus at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2013-03-28 10:00:42 UTC ---
(In reply to comment #3)
> Note the comment at line 728 of format.c where we must disable format caching
> when we encounter FMT_STRING.  The problem is related to saving a pointer to a
> string rather than the string itself.  That pointer can go out of scope on
> subsequent I/O operations so caching the format data will not work.

Well, one could save the data. The string is also stored in the hash:

  u->format_hash_table[hash].key = xmalloc (dtp->format_len);
  memcpy (u->format_hash_table[hash].key, dtp->format, dtp->format_len);

Thus, instead of saving it after the parsing as key, one can duplicate the
string and store it as dtp->format before parsing the string.

That's what I do in the patch, submitted at:
http://gcc.gnu.org/ml/fortran/2013-03/msg00155.html