[binutils-gdb] remote: Return NULL extra_info/name if they are empty

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a933405894161c8b15f675c48d077b7f7d6aabf2

commit a933405894161c8b15f675c48d077b7f7d6aabf2
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Mon Dec 11 21:05:30 2017 -0500

    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:
---
 gdb/ChangeLog |  6 ++++++
 gdb/remote.c  | 10 ++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 78fd713..6416c12 100644
--- 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 fe27713..852fdef 100644
--- 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;
     }