3 files changed, 165 insertions, 0 deletions
diff --git a/gdb/common/byte-vector.h b/gdb/common/byte-vector.h
new file mode 100644
index 0000000..c17b14d
--- /dev/null
+++ b/gdb/common/byte-vector.h
@@ -0,0 +1,62 @@
+/* Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef COMMON_BYTE_VECTOR_H
+#define COMMON_BYTE_VECTOR_H
+
+#include "common/def-vector.h"
+
+namespace gdb {
+
+/* byte_vector is a gdb_byte std::vector with a custom allocator that
+   unlike std::vector<gdb_byte> does not zero-initialize new elements
+   by default when the vector is created/resized.  This is what you
+   usually want when working with byte buffers, since if you're
+   creating or growing a buffer you'll most surely want to fill it in
+   with data, in which case zero-initialization would be a
+   pessimization.  For example:
+
+     gdb::byte_vector buf (some_large_size);
+     fill_with_data (buf.data (), buf.size ());
+
+   On the odd case you do need zero initialization, then you can still
+   call the overloads that specify an explicit value, like:
+
+     gdb::byte_vector buf (some_initial_size, 0);
+     buf.resize (a_bigger_size, 0);
+
+   (Or use std::vector<gdb_byte> instead.)
+
+   Note that unlike std::vector<gdb_byte>, function local
+   gdb::byte_vector objects constructed with an initial size like:
+
+     gdb::byte_vector buf (some_size);
+     fill_with_data (buf.data (), buf.size ());
+
+   usually compile down to the exact same as:
+
+     std::unique_ptr<byte[]> buf (new gdb_byte[some_size]);
+     fill_with_data (buf.get (), some_size);
+
+   with the former having the advantage of being a bit more readable,
+   and providing the whole std::vector API, if you end up needing it.
+*/
+using byte_vector = gdb::def_vector<gdb_byte>;
+
+} /* namespace gdb */
+
+#endif /* COMMON_DEF_VECTOR_H */
diff --git a/gdb/common/def-vector.h b/gdb/common/def-vector.h
new file mode 100644
index 0000000..ab9331f
--- /dev/null
+++ b/gdb/common/def-vector.h
@@ -0,0 +1,36 @@
+/* Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef COMMON_DEF_VECTOR_H
+#define COMMON_DEF_VECTOR_H
+
+#include <vector>
+#include "common/default-init-alloc.h"
+
+namespace gdb {
+
+/* A vector that uses an allocator that default constructs using
+   default-initialization rather than value-initialization.  The idea
+   is to use this when you don't want zero-initialization of elements
+   of vectors of trivial types.  E.g., byte buffers.  */
+
+template<typename T> using def_vector
+  = std::vector<T, gdb::default_init_allocator<T>>;
+
+} /* namespace gdb */
+
+#endif /* COMMON_DEF_VECTOR_H */
diff --git a/gdb/common/default-init-alloc.h b/gdb/common/default-init-alloc.h
new file mode 100644
index 0000000..4fb852f
--- /dev/null
+++ b/gdb/common/default-init-alloc.h
@@ -0,0 +1,67 @@
+/* Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef COMMON_DEFAULT_INIT_ALLOC_H
+#define COMMON_DEFAULT_INIT_ALLOC_H
+
+namespace gdb {
+
+/* An allocator that default constructs using default-initialization
+   rather than value-initialization.  The idea is to use this when you
+   don't want to default construct elements of containers of trivial
+   types using zero-initialization.  */
+
+/* Mostly as implementation convenience, this is implemented as an
+   adapter that given an allocator A, overrides 'A::construct()'.  'A'
+   defaults to std::allocator<T>.  */
+
+template<typename T, typename A = std::allocator<T>>
+class default_init_allocator : public A
+{
+public:
+  /* Pull in A's ctors.  */
+  using A::A;
+
+  /* Override rebind.  */
+  template<typename U>
+  struct rebind
+  {
+    /* A couple helpers just to make it a bit more readable.  */
+    typedef std::allocator_traits<A> traits_;
+    typedef typename traits_::template rebind_alloc<U> alloc_;
+
+    /* This is what we're after.  */
+    typedef default_init_allocator<U, alloc_> other;
+  };
+
+  /* Make the base allocator's construct method(s) visible.  */
+  using A::construct;
+
+  /* .. and provide an override/overload for the case of default
+     construction (i.e., no arguments).  This is where we construct
+     with default-init.  */
+  template <typename U>
+  void construct (U *ptr)
+    noexcept (std::is_nothrow_default_constructible<U>::value)
+  {
+    ::new ((void *) ptr) U; /* default-init */
+  }
+};
+
+} /* namespace gdb */
+
+#endif /* COMMON_DEFAULT_INIT_ALLOC_H */