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Re: [PATCH (for gdb)] enum-flags.h: Add trailing semicolon to example in comment


On Tue, 2018-06-05 at 18:31 +0100, Pedro Alves wrote:
> [adding gdb-patches]
> 
> On 06/05/2018 06:56 PM, David Malcolm wrote:
> > On Tue, 2018-06-05 at 17:13 +0100, Pedro Alves wrote:
> > > On 06/05/2018 03:49 PM, David Malcolm wrote:
> > > > On Tue, 2018-06-05 at 04:40 -0400, Trevor Saunders wrote:
> > > > > You may want to look at gdb's enum-flags.h which I think
> > > > > already
> > > > > implements what your doing here.
> > > > 
> > > > Aha!  Thanks!
> > > > 
> > > > Browsing the git web UI, that gdb header was introduced by
> > > > Pedro
> > > > Alves
> > > > in:
> > > >   https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=co
> > > > mmit
> > > > diff;h=8d297bbf604c8318ffc72d5a7b3db654409c5ed9
> > > > and the current state is here:
> > > >   https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=bl
> > > > ob;f
> > > > =gdb/common/enum-flags.h;hb=HEAD
> > > > 
> > > > I'll try this out with GCC; hopefully it works with C++98.
> > > 
> > > It should -- it was written/added while GDB still required C++98.
> > 
> > Thanks.
> > 
> > > Note I have a WIP series here:
> > > 
> > >  https://github.com/palves/gdb/commits/palves/cxx11-enum-flags
> > > 
> > > that fixes a few things, and adds a bunch of unit tests.  In
> > > the process, it uses C++11 constructs (hence the branch's name),
> > > but I think that can be reverted to still work with C++98.
> > > 
> > > I had seen some noises recently about GCC maybe considering
> > > requiring C++11.  Is that reasonable to expect in this cycle?
> > > (GDB requires GCC 4.8 or later, FWIW.)
> > 
> > I'm expecting that GCC 9 will still require C++98.
> 
> OK.
> 
> > 
> > > Getting that branch into master had fallen lower on my TODO,
> > > but if there's interest, I can try to finish it off soon, so we
> > > can share a better baseline.  (I posted it once, but found
> > > some issues which I fixed since but never managed to repost.)
> > 
> > Interestingly, it looks like gdb is using Google Test for
> > selftests;
> > gcc is using a hand-rolled API that is similar, but has numerous
> > differences (e.g. explicit calling of test functions, rather than
> > implicit test discovery).  So that's another area of drift between
> > the projects.
> 
> Nope, the unit tests framework is hand rolled too.  See
> gdb/selftest.h/c.
> It can be invoked with gdb's "maint selftest" command.
> You can see the list of tests with "maint info selftests", and
> you can pass a filter to "maint selftest" too.

Aha.  Thanks.  Looks like gdb and gcc each have different hand-rolled
selftest APIs:
* gdb's selftest.h/c has manual test registration; test failures are
handled via exceptions
* gcc's selftest.h/c has no test registration (test functions are
called explicitly); test failures are handled via "abort"

I'm not suggesting we try to unify these APIs at this time.

> > > > 
> > > > Presumably it would be good to share this header between GCC
> > > > and
> > > > GDB;
> > > > CCing Pedro; Pedro: hi!  Does this sound sane?
> > > > (for reference, the GCC patch we're discussing here is:
> > > >   https://gcc.gnu.org/ml/gcc-patches/2018-05/msg01685.html )
> > > 
> > > Sure!
> > 
> > Alternatively, if GCC needs to stay at C++98 and GDB moves on to
> > C++11,
> > then we can at least take advantage of this tested and FSF-assigned
> > C++98 code (better than writing it from scratch).
> 
> Agreed, but I'll try to see about making the fixes in the branch
> C++98 compatible.

Thanks.

> > 
> > I ran into one issue with the header, e.g. with:
> > 
> >   /* Dump flags type.  */
> >   DEF_ENUM_FLAGS_TYPE(enum dump_flag, dump_flags_t);
> > 
> > This doesn't work:
> >   TDF_SLIM | flags
> > but this does:
> >   flags | TDF_SLIM
> > where TDF_SLIM is one of the values of "enum dump_flag".
> 
> ISTR that that's fixed in the branch.

Interesting; I'll have a look.

> > BTW, I spotted this trivial issue in a comment in enum-flags.h
> > whilst
> > trying it out for gcc:
> > 
> > 
> > 
> > The DEF_ENUM_FLAGS_TYPE macro should be used with a trailing
> > semicolon, but the example in the comment lacks one.
> > 
> > 	* enum-flags.h: Add trailing semicolon to example in comment.
> 
> Thanks.  I've merged it.

Thanks.

[...snip...]

Dave


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