Re: "show remote foo-packet" regression (Re: [PATCH v2 1/3] gdb: Make global feature array a per-remote target array)

Andrew Burgess via Gdb-patches
2022-04-21T10:25:29Z

Pedro Alves <pedro@palves.net> writes:

> On 2022-04-18 20:01, Pedro Alves wrote:
>>
>> (gdb) show remote X-packet
>> Support for the 'p' packet on newly created remote targets is "disabled".
>>
>> and of course:
>>
>> (gdb) set remote X-packet disabled
>> "on", "off" or "auto" expected.
>>
>>
>> Also, BTW, err, why do we talk about the 'p' packet if the command is about
>> the X packet? That's busted. Seems like a preexisting issue in current master.
>
> I bisected this, and found out it was a regression introduced by this commit:
>
> 8579fd136a614985bd27f20539c7bb7c5a51287d is the first bad commit
> commit 8579fd136a614985bd27f20539c7bb7c5a51287d
> Author: Andrew Burgess <aburgess@redhat.com>
> Date: Mon Nov 8 14:58:46 2021 +0000
>
> gdb/gdbsupport: make xstrprintf and xstrvprintf return a unique_ptr
>
> The motivation is to reduce the number of places where unmanaged
> pointers are returned from allocation type routines. All of the
> callers are updated.
>
> There should be no user visible changes after this commit.
>
>
> This commit is present in the GDB 12 branch and not in GDB 11, so it's a regression there.

Sorry for the regression. I took a look at the code and I honestly have
no idea why I thought the code in the above commit would work :-/

Below is a patch that should fix this issue. I probably should write a
test to go along with it, but thought I'd share this for feedback first.

Let me know what you think,

Thanks,
Andrew

---

commit c4be5cb70bc9b67f7d465eb14a62a0692ed6ad94
Author: Andrew Burgess <aburgess@redhat.com>
Date: Thu Apr 21 11:16:18 2022 +0100

gdb: fix 'remote show FOO-packet' aliases

The following behaviour was observed in GDB:

(gdb) show remote X-packet
Support for the `p' packet is auto-detected, currently unknown.

Note the message mentions the 'p' packet. This is a regression since
this commit:

commit 8579fd136a614985bd27f20539c7bb7c5a51287d
Date: Mon Nov 8 14:58:46 2021 +0000

gdb/gdbsupport: make xstrprintf and xstrvprintf return a unique_ptr

Before this commit the behaviour was:

(gdb) show remote X-packet
Support for the `X' packet is auto-detected, currently unknown.

The problem was caused by a failed attempt to ensure that some
allocated strings were deleted when GDB exits. The code in the above
commit attempted to make use of 'static' to solve this problem,
however, the solution was just wrong.

In this new commit I instead allocate a static vector into which all
the allocated strings are stored, this ensures the strings are
released when GDB exits (which makes output from tools like valgrind
cleaner), but each string within the vector can be unique, which fixes
the regression.

diff --git a/gdb/remote.c b/gdb/remote.c
index 75d6bf3919d..562cc586f2b 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1968,15 +1968,17 @@ add_packet_config_cmd (struct packet_config *config, const char *name,
/* set/show remote NAME-packet {auto,on,off} -- legacy. */
if (legacy)
{
- /* It's not clear who should take ownership of this string, so, for
- now, make it static, and give copies to each of the add_alias_cmd
- calls below. */
- static gdb::unique_xmalloc_ptr<char> legacy_name
+ /* It's not clear who should take ownership of the LEGACY_NAME string
+ created below, so, for now, place the string into a static vector
+ which ensures the strings is released when GDB exits. */
+ static std::vector<gdb::unique_xmalloc_ptr<char>> legacy_names;
+ gdb::unique_xmalloc_ptr<char> legacy_name
= xstrprintf ("%s-packet", name);
add_alias_cmd (legacy_name.get (), cmds.set, class_obscure, 0,
&remote_set_cmdlist);
add_alias_cmd (legacy_name.get (), cmds.show, class_obscure, 0,
&remote_show_cmdlist);
+ legacy_names.emplace_back (std::move (legacy_name));
}
}