remote: Return NULL extra_info/name if they are empty

Commit

  remote: C++ify thread_item and threads_listing_context
  21fe1c752e254167d953fa8c846280f63a3a5290

broke the test gdb.threads/names.exp.  The problem is that since we now
use an std::string to hold the extra_info, an empty string is returned
by target_extra_thread_info to print_thread_info_1 when the remote stub
didn't send any extra info, instead of NULL before.  Because of that,
print_thread_info_1 prints the extra info between parentheses, which
results in some spurious empty parentheses.

  Expected: * 1    Thread 22752.22752 "main" all_threads_ready () at ...
  Actual  : * 1    Thread 22752.22752 "main" () all_threads_ready () a ...

Since the bug was introduced by a behavior change in the remote target,
I chose to fix it on the remote target side by making it return NULL
when the extra string is empty.  This will avoid possibly changing the
behavior of the common code and affecting other targets.

The name field has the same problem.  If a remote stub returns no thread
names, remote_thread_name will return an empty string instead of NULL,
so print_thread_info_1 will show empty quotes ("") instead of nothing.

gdb/ChangeLog:

	PR gdb/22556
	* remote.c (remote_thread_name): Return NULL if name is empty.
	(remote_threads_extra_info): Return NULL if extra info is empty.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 78fd713f91fef42f1d75e300cf774c049e974efa..6416c12a4947528d7f0d732aa7c8d10f9443d0a0 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-11  Simon Marchi  <simon.marchi@ericsson.com>
+
+       PR gdb/22556
+       * remote.c (remote_thread_name): Return NULL if name is empty.
+       (remote_threads_extra_info): Return NULL if extra info is empty.
+
 2017-12-11  Pedro Alves  <palves@redhat.com>
 
        * defs.h (elf_sym_fns_lazy_psyms, elf_sym_fns_gdb_index)

diff --git a/gdb/remote.c b/gdb/remote.c
index fe2771316cbc63c23302c71d96c01ebb65b95ce5..852fdef4903d6a4c83ff05bed9347d2e9ac86ad2 100644 (file)
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -2268,7 +2268,10 @@ static const char *
 remote_thread_name (struct target_ops *ops, struct thread_info *info)
 {
   if (info->priv != NULL)
-    return get_remote_thread_info (info)->name.c_str ();
+    {
+      const std::string &name = get_remote_thread_info (info)->name;
+      return !name.empty () ? name.c_str () : NULL;
+    }
 
   return NULL;
 }
@@ -3319,7 +3322,10 @@ remote_threads_extra_info (struct target_ops *self, struct thread_info *tp)
       struct thread_info *info = find_thread_ptid (tp->ptid);
 
       if (info != NULL && info->priv != NULL)
-       return get_remote_thread_info (info)->extra.c_str ();
+       {
+         const std::string &extra = get_remote_thread_info (info)->extra;
+         return !extra.empty () ? extra.c_str () : NULL;
+       }
       else
        return NULL;
     }