DMD currently outputs debug info differently depending on the switch you
pass it. Currently it works as follows:
-g Act as D, using D extensions
-gc Act as C, no D extensions
This leads to an odd situation for debugging (here I focus on
linux/other platforms that use DWARF, as my knowledge of debugging on
windows is rather limited). Let's assume you're using a patched version
of gdb or a sufficiently recent version from cvs/git.
Option 1: Compile with -g.
You fire up gdb with your crashing app. Oh look, gdb fails due to the D
extensions to DWARF which aren't supported yet (unless the hypothetical
app doesn't use dynamic arrays at all... what sort of app are you
writing? :D).
Option 2: Compile with -gc.
You fire up gdb with your crashing app. Gdb recognises all your files
end with .d and overrides the language setting, and gives you demangling
and a nice debugging environment. However C doesn't support things like
references, so all your classes appear as MyClass* rather than MyClass,
same goes for all your functions with ref args (See bug #4149, this
isn't the case yet, needs a small patch which I intend to write after
this post).
Of course neither of these options are ideal, so I'm wondering what the
correct way to proceed is. We have several options (in no particular order):
* Add more -g* options
Eww. Doing this we could enable acting like D without D extensions, or
acting like C++, or any number of other methods to get around the
problems. On the other hand, there's more options to confuse the user,
and they'll all be wondering why they have to compile with -gturnip
rather than -g to get working debug info.
* Remove the D extensions
We could remove the D extensions completely and stay within the spec.
DWARF 4 is in drafting now, we could request the few features get added
to the standard, then add in support when it's out. GCC is outputting
some DWARF4 already by default as of 4.5, so users aren't going to
complain about their ancient versions of gdb or other debuggers working.
I think this is the best option, and would volunteer to poke the
necessary people to get what we want in there.
* Patch GDB
This needs someone who's familiar enough with gdb to write a patch, and
it'll add ugliness to the source code from what I've seen of gdb's
internals... I'm not sure such a patch would get included, even if it is
possible to write one (I've just asked some gdb dev's, I'm awaiting a
reply).
* Change/replace the -gc option
Like the first option, but rather than adding a new -g* option, we
replace -gc to use a language that supports more features, and go from
there.
What I'm looking for is a consensus of some sort of what we think is the
best way forward for the debugging situation in D. Do you have any
better ideas than what I've suggested, or which of them do you think is
the best way for us to proceed?
Thanks for your input,
Robert
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