[llvm] r217756 - Fix a non-virtual destructor warning introduced in r217747.

[Hans Wennborg]

On Tue, Sep 16, 2014 at 10:00 AM, Frédéric Riss <friss at apple.com> wrote:
>
> On 16 Sep 2014, at 18:52, Hans Wennborg <hans at chromium.org> wrote:
>
> On Mon, Sep 15, 2014 at 12:33 PM, Frédéric Riss <friss at apple.com> wrote:
>
>
> On 15 Sep 2014, at 20:19, David Blaikie <dblaikie at gmail.com> wrote:
>
>
>
> On Mon, Sep 15, 2014 at 3:38 AM, Frederic Riss <friss at apple.com> wrote:
>
>
> Author: friss
> Date: Mon Sep 15 05:38:13 2014
> New Revision: 217756
>
> URL: http://llvm.org/viewvc/llvm-project?rev=217756&view=rev
> Log:
> Fix a non-virtual destructor warning introduced in r217747.
>
> Modified:
>    llvm/trunk/lib/DebugInfo/DWARFUnit.h
>
> Modified: llvm/trunk/lib/DebugInfo/DWARFUnit.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/DebugInfo/DWARFUnit.h?rev=217756&r1=217755&r2=217756&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/DebugInfo/DWARFUnit.h (original)
> +++ llvm/trunk/lib/DebugInfo/DWARFUnit.h Mon Sep 15 05:38:13 2014
> @@ -35,6 +35,8 @@ public:
>   /// Returns the Unit that contains the given section offset in the
>   /// same section this Unit originated from.
>   virtual DWARFUnit *getUnitForOffset(uint32_t Offset) const = 0;
> +
> +  virtual ~DWARFUnitSectionBase() {}
>
>
>
> Since these objects are never polymorphically owned, a better fix for this
> would be to make the base dtor protected, and the derived classes final.
> That will satisfy the warning without adding an unneeded vtable
> entry/virtual call overhead.
>
>
> I’ll do that in a followup commit tomorrow.
>
>
> This is causing problems for me after r217871:
>
> In file included from
> third_party/llvm/llvm/lib/DebugInfo/DWARFCompileUnit.h:13:0,
>                 from
> third_party/llvm/llvm/lib/DebugInfo/DWARFDebugInfoEntry.cpp:11:
> third_party/llvm/llvm/lib/DebugInfo/DWARFUnit.h: In instantiation of
> 'class llvm::DWARFUnitSection<llvm::DWARFCompileUnit>':
> third_party/llvm/llvm/lib/DebugInfo/DWARFContext.h:32:38:   required from
> here
> third_party/llvm/llvm/lib/DebugInfo/DWARFUnit.h:45:7: error: 'class
> llvm::DWARFUnitSection<llvm::DWARFCompileUnit>' has virtual functions
> and accessible non-virtual destructor [-Werror=non-virtual-dtor]
>
>
> With what compiler is that? I tested it with a fresh clang from master and
> it didn’t generate the warning. clang < 3.5 is known to produce a bogus
> warning in this case, but the build system should detect it and not pass
> -Wnon-virtual-dtor in that case.
>
> I won’t have time to look at this right now, if it is a blocking you and you
> can’t easily fix it, feel free to revert. (But I’d really like to understand
> the issue).

It's an internal build using GCC. I'm not entirely sure which version.
I know this has come up before, so I'm trying to understand what's
going on here and how it was fixed that time.

 - Hans