On Mon, Sep 10, 2018 at 04:40:58PM +0100, Jason Merrill wrote:
     On Mon, Sep 10, 2018 at 3:42 PM, John Darrington
     <john@darrington.wattle.id.au> wrote:
     > On Mon, Sep 10, 2018 at 03:36:26PM +0100, Jason Merrill wrote:
     >      On Mon, Aug 27, 2018 at 8:20 PM, John Darrington
     >      <john@darrington.wattle.id.au> wrote:
     >      >         * include/dwarf2.h (enum dwarf_unit_type) [DE_EH_PE_udata3]: New member.
     >
     >
     >      What's the rationale?  Do you have a separate patch that uses this new macro?
     >
     > Yes.   I there is an upcoming patch for GDB.  See
     > https://sourceware.org/ml/gdb-patches/2018-08/msg00731.html
     
     This looks like support for reading fixed 3-byte values from the
     exception handling unwind information.  Do you expect this information
     to ever need to store 3-byte values? 

Yes,  I've already come across that (which is why I created the patch).
Without this patch, GDB will barf.  See the attached backtrace.

     The offsets in the unwind info
     don't need to correspond exactly to target word sizes,

So far as I can tell, the dwarf-unwinder assumes that they do.  Chaning
it would require a rewrite.  I doubt the GDB team would be happy with
that.

     and if you use
     an assembler that supports it (such as GNU as), the table will use
     variable-length encoding anyway.

I must admit I don't understand what you are saying here.  I was using
GNU as.  To what table are you refering?
     

J'