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Re: [RFA/dwarf] save nested Ada subprograms as global symbol
- From: Daniel Jacobowitz <drow at false dot org>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Tue, 29 Jan 2008 12:16:10 -0500
- Subject: Re: [RFA/dwarf] save nested Ada subprograms as global symbol
- References: <20071227073938.GC10767@adacore.com>
On Wed, Dec 26, 2007 at 11:39:38PM -0800, Joel Brobecker wrote:
> The problem is trying to break on First:
>
> % gdb hello
> (gdb) break first
> Function "first" not defined.
> Make breakpoint pending on future shared library load? (y or [n]) n
>
> What we'd like to be able to do is:
>
> (gdb) b first
> Breakpoint 1 at 0x804954a: file hello.adb, line 6.
> (gdb) run
> Starting program: /home/no-backup/brobecke/ada-fsf/nested/hello
>
> Breakpoint 1, hello.first () at hello.adb:6
> 6 end First;
>
> To achieve this, we modified dwarf2read to store all Ada subprograms
> in the global scope, even the ones that are not "external". Another
> approach that was considered was to modify the Ada lookup routines
> to extend the search to non-global/static scopes, but I'm concerned
> about performance.
>
> In practice, even though these routines are indeed local to our
> procedure in the Ada program, we want to be flexible with the user
> in the debugger, and treat these procedures as global, so that the
> user can break inside them without specifying the scope or having
> to be in the scope where the function is defined.
Sorry, I really don't like this idea. What if you have a hello.first
and a goodbye.first? They're not related, so a breakpoint on "first"
landing in both spots would be strange.
A related example in C++ would be:
namespace A {
void first () { }
void second () { first (); }
}
int main()
{
A::second ();
}
GDB will not honor "break first" when stopped in main. But in second,
when the listed source line says "first ();", "break first" will work.
David Carlton did a lot of work to make this happen; the hook it uses
is cp_lookup_symbol_nonlocal. In practice, it seems to be the
behavior users expect.
--
Daniel Jacobowitz
CodeSourcery