[Bug other/46268] New: gengtype warning when GTY(()) markers have no effect

[Bug other/46268] New: gengtype warning when GTY(()) markers have no effect

[dnovillo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46268

           Summary: gengtype warning when GTY(()) markers have no effect
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dnovillo@gcc.gnu.org


Recently I was adding GTY markers to new structures but had forgotten to
declare a GC root variable.  This was causing gengtype to ignore the structure,
which meant that no ggc_alloc_cleared_XXX function was generated.  This caused
a failure during stage 2 when the compiler warned that no such function had
been declared.

The warning is removed from the immediate cause.  If gengtype had warned me
that I was adding a useless GTY marker, it would have made it easier to fix.

Additionally, the automatic generation of the ggc_... function family is not
very clearly documented in doc/gty.texi.

[Bug other/46268] gengtype warning when GTY(()) markers have no effect

[lauras at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46268

Laurynas Biveinis <lauras at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2010.11.10 05:02:53
     Ever Confirmed|0                           |1

--- Comment #1 from Laurynas Biveinis <lauras at gcc dot gnu.org> 2010-11-10 05:02:53 UTC ---
I have just committed documentation patch that should provide some help with
these issues.  The gengtype warning still needs to be implemented.

[Bug other/46268] gengtype warning when GTY(()) markers have no effect

[lauras at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46268

Laurynas Biveinis <lauras at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |SUSPENDED

--- Comment #2 from Laurynas Biveinis <lauras at gcc dot gnu.org> 2010-12-02 12:50:11 UTC ---
Currently straightforward implementation of this warning gives way too may
false positives.  To resolve them:

1) C preprocessor needs to be run on the gengtype input in order to resolve
conditionally defined types, fields, or types used only by some backends and
maybe help with vector issues too.

2) Vector macro machinery needs to be updated to sometimes output GTYs and
sometimes not.  This would cause a lot of leaking of implementation details to
the macro users.

The first one is a major roadblock for now.