Re: RFC: C/C++ preprocessor macro support for GDB

[Jim Blandy <jimb@redhat.com>]

For what it's worth:

Compiling GDB with -gdwarf-2 -g3 yields an executable with a 14Mb
.debug_macinfo section.  However, most of that is repetition; there is
actually only 247k of unique text in there.

The Dwarf 2 reader currently wants to pull the entire contents of
every .debug_mumble section it can find into memory.  So debugging
that GDB will increase the superior GDB's memory consumption by 14Mb.

However, the format-independent data structures that GDB builds from
that Dwarf 2 data use bcaches to store all the strings.  The bcaches
keep only one copy of any given string, and everyone just points at
those copies.  So those structures are well-behaved; all of GDB's
macro information would only occupy 247k + overhead in that form.