[PATCH] gdb: fix command lookup in execute_command ()

[Jan Vrany <jan.vrany@labware.com>]

Hi,

> I've spotted gdb.base/define.exp failing today, and bisection stopped in this particular
> patch.

> target testsuite
> one
> hello
> (gdb) FAIL: gdb.base/define.exp: target testsuite with hooks

My fault, I did not consider the case of hooks on subcommands
(I was not even conciously aware this is possible).

The below patch should fix this case - with it on my system
gdb.base/define.exp passes.

Alternatively I may just revert the commit until better solution
is found.

-- >8 --
Subject: [PATCH] gdb: fix command lookup in execute_command ()

Commit b5661ff2 ("gdb: fix possible use-after-free when
executing commands") used lookup_cmd_exact () to lookup
command again after its execution to avoid possible
use-after-free error.

However this change broke test gdb.base/define.exp which
defines a post-hook for subcommand ("target testsuite").
In this case,  lookup_cmd_exact () returned NULL because
there's no command 'testsuite' in top-level commands.

This commit fixes this case by looking up the command again
using the original command line via lookup_cmd ().
---
 gdb/top.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/gdb/top.c b/gdb/top.c
index 742997808bd..caa08d98cec 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -655,11 +655,6 @@ execute_command (const char *p, int from_tty)
 	    }
 	}
 
-      /* Remember name of the command.  This is needed later when
-	 executing command post-hooks to handle the case when command
-	 is redefined or removed during it's execution.  See below.  */
-      std::string c_name (c->name);
-
       /* If this command has been pre-hooked, run the hook first.  */
       execute_cmd_pre_hook (c);
 
@@ -702,7 +697,8 @@ execute_command (const char *p, int from_tty)
 	 We need to lookup the command again since during its execution,
 	 a command may redefine itself.  In this case, C pointer
 	 becomes invalid so we need to look it up again.  */
-      c = lookup_cmd_exact (c_name.c_str (), cmdlist);
+      const char *cmd2 = cmd_start;
+      c = lookup_cmd (&cmd2, cmdlist, "", nullptr, 1, 1);
       if (c != nullptr)
 	execute_cmd_post_hook (c);
 
-- 
2.35.1