libstdc++: shrink-to-fit in std::basic_stacktrace::current(skip, max)

If a large stacktrace is reduced to a max depth that is less than half
the capacity it will now be reallocated to remove the unused capacity.

libstdc++-v3/ChangeLog:

	* include/std/stacktrace (basic_stacktrace::current): Reallocate
	a smaller container if the unused capacity is larger than the
	used size.

diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index 382d900a822fe09f1c52c1a59d5b5364e9b686d3..98ce92311501515f2cf799ae2dd48a055882aaf3 100644 (file)
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -289,7 +289,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            if (__err < 0)
              __ret._M_clear();
            else if (__ret.size() > __max_depth)
-             __ret._M_impl._M_resize(__max_depth, __ret._M_alloc);
+             {
+               __ret._M_impl._M_resize(__max_depth, __ret._M_alloc);
+
+               if (__ret._M_impl._M_capacity / 2 >= __max_depth)
+                 {
+                   // shrink to fit
+                   _Impl __tmp = __ret._M_impl._M_clone(__ret._M_alloc);
+                   if (__tmp._M_capacity)
+                     {
+                       __ret._M_clear();
+                       __ret._M_impl = __tmp;
+                     }
+                 }
+             }
          }
        return __ret;
       }