[Dwarf-Discuss] how to find local variable stored in register

Michael Eager eager@eagercon.com
Wed Feb 6 01:52:43 GMT 2008

Jim Blandy wrote:
> On Feb 5, 2008 2:43 PM, Daniel Jacobowitz <drow at false.org> wrote:
>> I think 16.1% of executable size is huge.  .debug_frame is normally,
>> what, 2-3% of executable size?
> A lot of people at Mozilla didn't know that the GNU toolchain
> supported C preprocessor macro debugging information; they've started
> using it now.  Because DWARF doesn't allow different CUs' macro
> information to share strings, .debug_macinfo ends up being 12x the
> size of .text.  I told them, "It's a bit bulky; you might want to
> check your build tree sizes." Nobody cares.  They love it.
> Different organizations have different concerns.  I think it's a
> mistake for GCC to assume that a GiB is precious; it's not so for many
> real-world organizations.

You may be correct, but size reduction has been the single most
common justification for changes to the DWARF standard.  Just
a few months ago you were advocating a change (which was adopted)
to replace the DW_AT_high_pc value with an LEB offset, saving a
couple bytes in each subprogram DIE.  I believe that you found a 3%
reduction in the size of the reloc table and a similarly modest
size savings in the .dwarf_debug section.

Michael Eager	 eager at eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077

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