[Bug libfortran/66650] New: libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[Bug libfortran/66650] New: libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

            Bug ID: 66650
           Summary: libgfortran: warning: left shift of negative value
                    [-Wshift-negative-value]
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tschwinge at gcc dot gnu.org
                CC: mpolacek at gcc dot gnu.org
  Target Milestone: ---

As of the changes in context of PR65179,
<http://news.gmane.org/find-root.php?message_id=%3C20150422183633.GI28950%40redhat.com%3E>,
I'm seeing a bunch of -Wshift-negative-value warnings in the libgfortran build,
for example:

    In file included from [...]/libgfortran/intrinsics/cshift0.c:26:0:
    [...]/libgfortran/intrinsics/cshift0.c: In function 'cshift0':
    [...]/libgfortran/libgfortran.h:408:48: warning: left shift of negative
value [-Wshift-negative-value]
       ((~((index_type) 0) >> GFC_DTYPE_SIZE_SHIFT) << GFC_DTYPE_SIZE_SHIFT)
                                                    ^
    [...]/libgfortran/libgfortran.h:409:35: note: in expansion of macro
'GFC_DTYPE_SIZE_MASK'
     #define GFC_DTYPE_TYPE_SIZE_MASK (GFC_DTYPE_SIZE_MASK |
GFC_DTYPE_TYPE_MASK)
                                       ^
    [...]/libgfortran/libgfortran.h:411:52: note: in expansion of macro
'GFC_DTYPE_TYPE_SIZE_MASK'
     #define GFC_DTYPE_TYPE_SIZE(desc) ((desc)->dtype &
GFC_DTYPE_TYPE_SIZE_MASK)
                                                        ^
    [...]/libgfortran/intrinsics/cshift0.c:94:15: note: in expansion of macro
'GFC_DTYPE_TYPE_SIZE'
       type_size = GFC_DTYPE_TYPE_SIZE (array);
                   ^

Unless this will be resolved by demoting the warning (I have not reviewed the
recent discussion, such as PR66066,
<http://news.gmane.org/find-root.php?message_id=%3C20150511142112.GO3384%40redhat.com%3E>),
I supposed this should be fixed in libgfortran/libgfortran.h, perhaps by making
index_type an unsiged type if that's possible?

[Bug libfortran/66650] libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
Patch that rewrites GFC_DTYPE_SIZE_MASK definition to avoid "left shift of
negative value" warning:

--cut here--
Index: libgfortran.h
===================================================================
--- libgfortran.h       (revision 226339)
+++ libgfortran.h       (working copy)
@@ -404,8 +404,7 @@

 /* Macros to get both the size and the type with a single masking operation 
*/

-#define GFC_DTYPE_SIZE_MASK \
-  ((~((index_type) 0) >> GFC_DTYPE_SIZE_SHIFT) << GFC_DTYPE_SIZE_SHIFT)
+#define GFC_DTYPE_SIZE_MASK (-((index_type) 1 << GFC_DTYPE_SIZE_SHIFT))
 #define GFC_DTYPE_TYPE_SIZE_MASK (GFC_DTYPE_SIZE_MASK | GFC_DTYPE_TYPE_MASK)

 #define GFC_DTYPE_TYPE_SIZE(desc) ((desc)->dtype & GFC_DTYPE_TYPE_SIZE_MASK)
--cut here--
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg055

--- Comment #5 from Henning Baldersheim <balder@yahoo-inc.com> ---
Actually -fno-inline-functions was enough as a workaround. Then I can still use
the same general -O3 option.

[Bug libfortran/66650] libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

--- Comment #3 from uros at gcc dot gnu.org ---
Author: uros
Date: Wed Jul 29 15:42:03 2015
New Revision: 226355

URL: https://gcc.gnu.org/viewcvs?rev=226355&root=gcc&view=rev
Log:
        PR libgfortran/66650
        * libgfortran.h (GFC_DTYPE_SIZE_MASK): Rewrite to avoid
        "left shift of negative value" warning.


Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/libgfortran.h

[Bug libfortran/66650] libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

--- Comment #4 from uros at gcc dot gnu.org ---
Author: uros
Date: Wed Jul 29 17:12:28 2015
New Revision: 226357

URL: https://gcc.gnu.org/viewcvs?rev=226357&root=gcc&view=rev
Log:
        PR libgfortran/66650
        * libgfortran.h (GFC_DTYPE_SIZE_MASK): Rewrite to avoid
        "left shift of negative value" warning.


Modified:
    branches/gcc-5-branch/libgfortran/ChangeLog
    branches/gcc-5-branch/libgfortran/libgfortran.h

[Bug libfortran/66650] libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

--- Comment #5 from uros at gcc dot gnu.org ---
Author: uros
Date: Wed Jul 29 17:45:07 2015
New Revision: 226360

URL: https://gcc.gnu.org/viewcvs?rev=226360&root=gcc&view=rev
Log:
        PR libgfortran/66650
        * libgfortran.h (GFC_DTYPE_SIZE_MASK): Rewrite to avoid
        "left shift of negative value" warning.


Modified:
    branches/gcc-4_9-branch/libgfortran/ChangeLog
    branches/gcc-4_9-branch/libgfortran/libgfortran.h

[Bug libfortran/66650] libgfortran: warning: left shift of negative value [-Wshift-negative-value]

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66650

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
           Assignee|unassigned at gcc dot gnu.org      |ubizjak at gmail dot com
   Target Milestone|---                         |4.9.4

--- Comment #6 from Uroš Bizjak <ubizjak at gmail dot com> ---
Fixed everywhere.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg058

--- Comment #2 from Lenjoy <mars.lenjoy at gmail dot com> ---
(In reply to Markus Trippelsdorf from comment #1)
> This is an LLVM bug.

okay, filed https://llvm.org/bugs/show_bug.cgi?id$304