[PATCH] Use string_file::release in some places

[Tom Tromey via Gdb-patches <gdb-patches@sourceware.org>]

I found a few spots like:

    string_file f;
    std::string x = f.string ();

However, string_file::string returns a 'const std::string &'...  so it
seems to me that this must be copying the string (? I find it hard to
reason about this in C++).

This patch changes these spots to use release() instead, which moves
the string.
---
 gdb/breakpoint.c | 2 +-
 gdb/top.c        | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index d807ae3c9b5..f9b20a7d62d 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -7581,7 +7581,7 @@ bp_location::to_string () const
   string_file stb;
   ui_out_redirect_pop redir (current_uiout, &stb);
   print_breakpoint_location (this->owner, this);
-  return stb.string ();
+  return stb.release ();
 }
 
 /* Decrement reference count.  If the reference count reaches 0,
diff --git a/gdb/top.c b/gdb/top.c
index 2322e55f1db..cbe14b01046 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -647,12 +647,12 @@ execute_fn_to_string (std::string &res, std::function<void(void)> fn,
   catch (...)
     {
       /* Finally.  */
-      res = std::move (str_file.string ());
+      res = str_file.release ();
       throw;
     }
 
   /* And finally.  */
-  res = std::move (str_file.string ());
+  res = str_file.release ();
 }
 
 /* See gdbcmd.h.  */
-- 
2.40.1