[Bug fortran/61632] Memory corruption on error when writing formatted data

["dominiq at lps dot ens.fr" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61632

--- Comment #22 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> Created attachment 33160 [details]
> Updated patch taking care of valgrind error
>
> This patch includes fixing the valgrind error by allocating and setting
> the NULL byte at the end of the format string.

With this patch all my tests for this PR pass without problem: no more memory
corruption and the caret is at the right position!-).

I have two questions:

(1) my understanding of 

  offset = (j > 60) ? j - 40 : 0;

  j -= offset;
  width = dtp->format_len - offset;

is to set j to 40 and to decrease width by j-40 if j>60.

This part is now removed, should not we limit offset to something?

(2) Do you need me to package one or two of my tests for the caret position?

Indeed I'ld perfectly happy if the behavior reported in comment 10 would be at
least understood. Note that with the code

      program p
      call ss0()
      call ss()
      end program p
      subroutine ss0
      CHARACTER(3), save :: ZTYP(4)
      DATA ZTYP /'WWW','XXX','YYY','ZZZ'/
      write(10,500,err=10,iostat=iosa) 'AAA','BBB',0.0,ZTYP
 500  FORMAT(2(A3),1PE13.5,A3)
      return
 10   write(10, *)
      write(10, *) 'iostat =', iosa
      end subroutine ss0
      subroutine ss
      CHARACTER(3), save :: ZTYP(4)
      DATA ZTYP /'WWW','XXX','YYY','ZZZ'/
      write(10,600) 'AAA','BBB',0.0,ZTYP
 600  FORMAT(A3,1PE13.5,2(A3))
      end subroutine ss

gives at run time

[Book15] f90/bug% cat fort.10
AAABBB  0.00000E+00WWW

 iostat =        5006

but my mother is saying "le mieux est l'ennemi du bien" (~ the best is against
the good) so I think this should not defer the commit of the patch.