fix geometry_batcher copy semantics and add move operations

clone() allocated fresh vert/radius_list buffers without freeing the
ones already owned, so assigning over a live batcher leaked both.  It
also never copied buffer_offset, and the copy constructor called it
with no member initialization at all -- so every copy-constructed
batcher carried an uninitialized buffer_offset.  Free the existing
buffers in clone(), copy buffer_offset, and delegate the copy
constructor to the default constructor so clone() sees initialized
members (which is also what makes its new frees safe on that path).

Also add noexcept move operations, which the user-declared copy
operations had suppressed, so by-value handling can transfer the
buffers instead of deep-copying them.

None of these defects were reachable from current callers (the static
batch maps mutate entries in place); this closes the latent hazards.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Goober5000

code/graphics/grbatch.cpp

@@ -13,6 +13,8 @@
 #include "graphics/grbatch.h"
 #include "render/3d.h"
 
+#include <utility>
+
 geometry_batcher::~geometry_batcher()
 {
 	if (vert != NULL) {
@@ -124,6 +126,15 @@ void geometry_batcher::clone(const geometry_batcher &geo)
 	n_to_render = geo.n_to_render;
 	n_allocated = geo.n_allocated;
 	use_radius = geo.use_radius;
+	buffer_offset = geo.buffer_offset;
+
+	// free any buffers we already own, so that assignment doesn't leak them
+	if (vert != nullptr) {
+		vm_free(vert);
+	}
+	if (radius_list != nullptr) {
+		vm_free(radius_list);
+	}
 
 	if (n_allocated > 0) {
 		vert = (vertex *) vm_malloc( sizeof(vertex) * n_allocated );
@@ -146,6 +157,37 @@ geometry_batcher& geometry_batcher::operator=(const geometry_batcher &geo)
 	return *this;
 }
 
+geometry_batcher::geometry_batcher(geometry_batcher &&other) noexcept
+	: n_to_render(std::exchange(other.n_to_render, 0)),
+	  n_allocated(std::exchange(other.n_allocated, 0)),
+	  vert(std::exchange(other.vert, nullptr)),
+	  use_radius(std::exchange(other.use_radius, true)),
+	  radius_list(std::exchange(other.radius_list, nullptr)),
+	  buffer_offset(std::exchange(other.buffer_offset, -1))
+{
+}
+
+geometry_batcher& geometry_batcher::operator=(geometry_batcher &&other) noexcept
+{
+	if (this != &other) {
+		if (vert != nullptr) {
+			vm_free(vert);
+		}
+		if (radius_list != nullptr) {
+			vm_free(radius_list);
+		}
+
+		n_to_render = std::exchange(other.n_to_render, 0);
+		n_allocated = std::exchange(other.n_allocated, 0);
+		vert = std::exchange(other.vert, nullptr);
+		use_radius = std::exchange(other.use_radius, true);
+		radius_list = std::exchange(other.radius_list, nullptr);
+		buffer_offset = std::exchange(other.buffer_offset, -1);
+	}
+
+	return *this;
+}
+
 /*
 0----1
 |\   |

code/graphics/grbatch.h

@@ -32,8 +32,12 @@ class geometry_batcher
 	geometry_batcher(): n_to_render(0), n_allocated(0), vert(NULL), use_radius(true), radius_list(NULL), buffer_offset(-1) {}
 	~geometry_batcher();
 
-    geometry_batcher(const geometry_batcher &geo) { clone(geo); }
-    geometry_batcher& operator=(const geometry_batcher &geo);
+	// delegate to the default constructor so that clone() sees initialized members
+	geometry_batcher(const geometry_batcher &geo) : geometry_batcher() { clone(geo); }
+	geometry_batcher& operator=(const geometry_batcher &geo);
+
+	geometry_batcher(geometry_batcher &&other) noexcept;
+	geometry_batcher& operator=(geometry_batcher &&other) noexcept;
 
 	// initial memory space needed
 	// NOTE: This MUST be called BEFORE calling any of the draw_*() functions!!