gc-sections and DWARF ranges

[Daniel Jacobowitz]

I found a test today where GDB fails to find symbol info.  It's not
GDB's fault, though: there's an input .o file which has eleven entries
in .debug_ranges, and then there's only nine by the end of the link.
The tenth was for a GC'd section.  The eleventh, by bad luck, happens
to be main.

Cary fixed a specific case of this problem in GCC by emitting fewer ranges:

  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42454

That doesn't solve the general problem if there's actual garbage
collection.

Is there any provision in GNU ld for this that I'm not seeing?  We
ought to remove discarded entries with knowledge of the .debug_ranges
output; I don't see how we can get this right otherwise.

I can make a good argument that every debug section with references to
the discarded section must have special processing, or we are
generating broken debug output - GDB's workaround for functions at
address 0 is another case.  That one can be solved by use of section
groups, but the compile unit's .debug_ranges has to be a single entity.

-- 
Daniel Jacobowitz
CodeSourcery