From: Martin Galvan <martin.galvan@tallertechnologies.com>
To: Pedro Alves <palves@redhat.com>
Cc: gdb-patches <gdb-patches@sourceware.org>
Subject: Re: [PATCH v2] Fix gdb crash when trying to print the address of a synthetic pointer.
Date: Sun, 28 Jun 2015 05:06:00 -0000 [thread overview]
Message-ID: <CAOKbPbbg-VV77=3KKYu=fYZPQonSWNesRyJjq_34rXq9R7SyqQ@mail.gmail.com> (raw)
In-Reply-To: <558A90D7.30505@redhat.com>
On Wed, Jun 24, 2015 at 8:13 AM, Pedro Alves <palves@redhat.com> wrote:
> On 06/20/2015 04:25 AM, Martin Galvan wrote:
>> Yes, 'function' ends up inlined. If we try to set a breakpoint at a
>> line inside 'function', the breakpoint will be set at an address we'll
>> never hit, thus we need to advance using 'step' and 'next' instead.
>
> Then it sounds like you were putting a breakpoint at a line that was
> optimized out. If you put the breakpoint at the same line that you
> "step" and "next" to, then it should work, I think. You'll still
> need a "step" to go from real stack frame to inline frame, as GDB always
> presents you the stack frame on breakpoint hits.
That's what I tried at the beginning. However, if I set the breakpoint
at the line I step to, using "continue" will either take me to an
address after the one I want to stop at, or just finish the program.
> Hmm, that looks too long to me and still escaping out a detail
> that isn't really that interesting to the user. I was just thinking:
>
> if (is reference)
> "Attempt to take address of a synthetic reference."
> else
> "Attempt to take address of a synthetic pointer."
The case on which the variable is an actual synthetic pointer (as
opposed to a synthetic reference) doesn't seem to reach value_addr;
instead it prints the "Can't take address of foo which isn't an
lvalue" message from address_of_variable.
If you think it's ok, I'll print "Attempt to take address of a
synthetic reference" at value_addr, and move the check inside the
TYPE_CODE_REF path.
>> I haven't been able to test this so far because the test requires an
>> x86-like target, which I don't have at hand. I'll keep you posted,
>> though.
>
> Do you have an x86-64 box? If so, you can just run the test with:
>
> make check RUNTESTFLAGS="--target_board=unix/-m32 gdb.dwarf2/implptr.exp"
That worked alright. Is this documented somewhere?
>> Assuming gdb crashes there too, couldn't I just add a "print &j" test
>> there and discard the synthetic-pointer-reference.exp test altogether?
>
> Actually from your description, I assume it _doesn't_ crash, because it's
> not a reference. But it's not tested presently, so who know. I think it's
> worth it to have both pointers and references covered.
You're right, it doesn't crash. I'll still add a test to implptr.exp
to catch the "Can't take address of foo which isn't an lvalue"
message, though.
About not using printf inside synthetic-pointer-reference.cc, is there
any way to make sure gcc won't optimize 'arg' out completely other
than that? Declaring it as volatile doesn't seem to work.
next prev parent reply other threads:[~2015-06-28 5:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-14 4:49 Martin Galvan
2015-06-15 11:17 ` Pedro Alves
2015-06-20 3:25 ` Martin Galvan
2015-06-24 11:13 ` Pedro Alves
2015-06-28 5:06 ` Martin Galvan [this message]
2015-06-30 10:46 ` Pedro Alves
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