[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

-- 

fxcoudert at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Keywords||wrong-code
  Known to fail||4.3.0
   Last reconfirmed|-00-00 00:00:00 |2007-08-15 13:05:53
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

--- Comment #1 from fxcoudert at gcc dot gnu dot org  2007-08-15 14:05 
---
The problem is shared by the TRIM and MIN/MAX. It is demonstrated by:

  character(len=1) :: s
  character(len=0) :: s0
  s = " "
  s0 = ""
  call bar ("")
  call bar (s)
  call bar (s0)
  call bar (trim(s))
  call bar (min(s0,s0))
contains
  subroutine bar (s)
character(len=*), optional :: s
if (.not. present (S)) call abort
  end subroutine bar
end

The problem is that a zero-length character string isn't NULL, it's "" (ie a
pointer to a '\0'). The following patch fixes it:

Index: intrinsics/string_intrinsics.c
===
--- intrinsics/string_intrinsics.c  (revision 127490)
+++ intrinsics/string_intrinsics.c  (working copy)
@@ -167,16 +167,21 @@ string_trim (GFC_INTEGER_4 * len, void *
 }
   *len = i + 1;

-  if (*len > 0)
+  if (*len == 0)
+{
+  /* A zero-length Fortran string is "".  */
+  char * tmp = internal_malloc_size (1);
+  tmp[0] = '\0';
+  *dest = tmp;
+}
+  else
 {
   /* Allocate space for result string.  */
   *dest = internal_malloc_size (*len);

-  /* copy string if necessary.  */
+  /* Copy string if necessary.  */
   memmove (*dest, src, *len);
 }
-  else
-*dest = NULL;
 }


@@ -403,14 +408,18 @@ string_minmax (GFC_INTEGER_4 *rlen, void
 }
   va_end (ap);

-  if (*rlen > 0)
+  if (*rlen == 0)
+{
+  /* A zero-length Fortran string is "".  */
+  char * tmp = internal_malloc_size (1);
+  tmp[0] = '\0';
+  *dest = tmp;
+}
+  else
 {
   char * tmp = internal_malloc_size (*rlen);
   memcpy (tmp, res, reslen);
   memset (&tmp[reslen], ' ', *rlen - reslen);
   *dest = tmp;
 }
-  else
-*dest = NULL;
 }
-


-- 

fxcoudert at gcc dot gnu dot org changed:

   What|Removed |Added

 AssignedTo|unassigned at gcc dot gnu   |fxcoudert at gcc dot gnu dot
   |dot org |org
 Status|NEW |ASSIGNED
   Keywords||patch
   Last reconfirmed|2007-08-15 13:05:53 |2007-08-15 14:05:29
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[schwab at suse dot de]

--- Comment #2 from schwab at suse dot de  2007-08-15 14:18 ---
Why do you need to special case len == 0?  The other strings aren't NUL
terminated either.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

--- Comment #3 from fxcoudert at gcc dot gnu dot org  2007-08-15 14:22 
---
(In reply to comment #2)
> Why do you need to special case len == 0?  The other strings aren't NUL
> terminated either.

The zero-termination is just a detail to avoid keeping memory uninitialized.
The thing is that *dest should not be NULL, and malloc(0) will return NULL.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

-- 

fxcoudert at gcc dot gnu dot org changed:

   What|Removed |Added

URL||http://gcc.gnu.org/ml/gcc-
   ||patches/2007-
   ||08/msg01012.html
   Target Milestone|--- |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[patchapp at dberlin dot org]

--- Comment #4 from patchapp at dberlin dot org  2007-08-16 13:25 ---
Subject: Bug number PR33079

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01012.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

--- Comment #5 from fxcoudert at gcc dot gnu dot org  2007-08-17 13:09 
---
Subject: Bug 33079

Author: fxcoudert
Date: Fri Aug 17 13:09:23 2007
New Revision: 127584

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=127584
Log:
PR fortran/33079

* intrinsics/string_intrinsics.c (string_trim, string_minmax): Fix
the zero-length result case.

* gfortran.dg/zero_length_2.f90: New test.

Added:
trunk/gcc/testsuite/gfortran.dg/zero_length_2.f90
Modified:
trunk/gcc/testsuite/ChangeLog
trunk/libgfortran/ChangeLog
trunk/libgfortran/intrinsics/string_intrinsics.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079

[Bug libfortran/33079] Optional empty strings do not appear to be 'PRESENT'

[fxcoudert at gcc dot gnu dot org]

--- Comment #6 from fxcoudert at gcc dot gnu dot org  2007-08-17 13:10 
---
Fixed.


-- 

fxcoudert at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution||FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33079