Re: [patch] Add printing of .gdb_index section to readelf

[Mark Wielaard <mjw at redhat dot com>]

Hi Roland,

> I'm dubious about this. The .gdb_index format is not
> standardized even in the GNU sense.

How does GNU standardization work BTW?
Is there some GNU tools list?

> It's entirely gdb's private business. Unless and until
> it becomes a standard thing that an elfutils tool could generate
> itself by well-specified rules not involving language-specific
> knowledge, I think this belongs in its own gdb-specific tool.

I don't think it involves any language-specific knowledge. And
although the documentation is somewhat hidden (see the comment
in the patch where to find it). I could write this just by going
from the documentation.

On the one hand I agree, it is a somewhat odd section. And I
was actually going to suggest that it gets generated as something
separate. Currently it takes up about ~10% of the .debug files.

On the other hand, it is kind of standard now, and is part of
the standard elf sections even we already recognize in ebl.
Which means tools like eu-strip for example already handle it
specially. And since it does take up so much space in the
standard separate debuginfo files it makes sense to want to
inspect it. It is also properly versioned, so we can recognize
whether or not we can parse it. And seeing it is so big, we
really should look into either making it work with other
tools, or look at what it provides gdb, so we can improve
the standard indexes to make other tools also benefit.

What about a compromise? We don't print is by default
with -w/--dump-debug, but only when explicitly requested?

diff --git a/src/readelf.c b/src/readelf.c
index 7250bb3..f4b427e 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -189,11 +189,12 @@ static enum section_e
   section_macinfo = 256,       /* .debug_macinfo  */
   section_ranges = 512,        /* .debug_ranges  */
   section_exception = 1024,    /* .eh_frame & al.  */
-  section_gdb_index = 2048,    /* .gdb_index  */
+  section_gdb_index = 2048,    /* .gdb_index, like a .debug section,
+                                  but not printed by default.  */
   section_all = (section_abbrev | section_aranges | section_frame
                 | section_info | section_line | section_loc
                 | section_pubnames | section_str | section_macinfo
-                | section_ranges | section_exception | section_gdb_index)
+                | section_ranges | section_exception)
 } print_debug_sections, implicit_debug_sections;
 
 /* Select hex dumping of sections.  */


Thanks,

Mark