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Re: bfd Mach-O DWARF debugging support

Hi Albert,

On 8 Apr 2012, at 11:07, Albert Zeyer wrote:

It seems that the binary references to `.o` files.

Yes and I believe that we have partial support already in gdb, but maybe not elsewhere in binutils (Tristan would know better).


That is also where
`dsymutil` is collecting its debug info from.

.. the reason for dsymutil's existence is that when you do "gcc foo.c - g -o foo" the intermediate object files are temporary - deleted at the end of the compile - so that they cannot be found later for debug etc.

dsymutil intercepts them before they are removed and copies the debug info.

if you build every source with "-c" and then link separately this problem might not arise (providing you keep the .o files where they were built).

if you are doing a single file with a c/l like about - one thing you can try is to add "-save-temps" so that the intermediate object is saved.

(or dsymutil, of course)

however, AFAIR, Apple's gcc automatically invokes dsymutil when "-g*" is on the c/l for Darwin >= 9 (osx 10.5) or if -g-dwarf* is explicitly stated.

FSF GCC also does the same (and for a wider range of languages).

Apples GDB and other Apple tools read this referenced debug info.
Maybe libbfd should too?

I am sure that there are (possibly large) gaps in our support.
It would be very nice if we had complete support for this -- patches welcome!
(darwin has only a small group of volunteers, the more the merrier!)



On Fri, Apr 6, 2012 at 5:13 AM, Albert Zeyer <> wrote:

I was wondering about the current state of the Mach-O DWARF debugging
support. I saw some patches recently which implemented
`bfd_mach_o_find_nearest_line` (that is mostly what I am interested

I have a binary which was build via `gcc -gdwarf-2` (Apples GCC).

I tried binutils-2.22.52 but it doesn't really work for me. I tried to
debug it a bit. Some things I can say so far:

* `objdump -g` doesn't output anything regarding debugging info.
* In bfd/dwarf2.c, in find_line(), _bfd_dwarf2_slurp_debug_info returns false.
* In _bfd_dwarf2_slurp_debug_info(), find_debug_info returns false.
* `objdump -h` doesn't list any debug section.

When I use `dsymutil` to generate a dSYM from my binary,
`bfd_mach_o_find_nearest_line` works.

Can somebody give some hints wether it should work or about the current state?


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