From 520162f36a0ff188b5b3db89d095c0660ad562f2 Mon Sep 17 00:00:00 2001
From: Jonas Kulla <Nyocurio@gmail.com>
Date: Thu, 9 Oct 2014 19:02:29 +0200
Subject: [PATCH] Use safe way to get at a vector's data pointer

&std::vector<C>[0] is not guaranteed to not throw if the
vector is empty. Better safe than sorry.
---
 binding-mruby/mrb-ext/rwmem.cpp |  2 +-
 src/global-ibo.h                |  2 +-
 src/quadarray.h                 |  4 ++--
 src/tileatlasvx.cpp             |  2 +-
 src/tilemap.cpp                 |  6 +++---
 src/tilemapvx.cpp               |  4 ++--
 src/util.h                      | 13 +++++++++++++
 src/windowvx.cpp                |  6 +++---
 8 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/binding-mruby/mrb-ext/rwmem.cpp b/binding-mruby/mrb-ext/rwmem.cpp
index 7245ffd..1c83061 100644
--- a/binding-mruby/mrb-ext/rwmem.cpp
+++ b/binding-mruby/mrb-ext/rwmem.cpp
@@ -101,7 +101,7 @@ int RWMemGetData(SDL_RWops *ops, void *buffer)
 	ByteVec *v = getRWPrivate(ops);
 
 	if (buffer)
-		memcpy(buffer, &(*v)[0], v->size());
+		memcpy(buffer, dataPtr(*v), v->size());
 
 	return v->size();
 }
diff --git a/src/global-ibo.h b/src/global-ibo.h
index 77ff555..c8beaf3 100644
--- a/src/global-ibo.h
+++ b/src/global-ibo.h
@@ -67,7 +67,7 @@ struct GlobalIBO
 		}
 
 		IBO::bind(ibo);
-		IBO::uploadData(buffer.size() * sizeof(index_t), &buffer[0]);
+		IBO::uploadData(buffer.size() * sizeof(index_t), dataPtr(buffer));
 		IBO::unbind();
 	}
 };
diff --git a/src/quadarray.h b/src/quadarray.h
index f4037ed..8751739 100644
--- a/src/quadarray.h
+++ b/src/quadarray.h
@@ -86,7 +86,7 @@ struct QuadArray
 		{
 			/* New data exceeds already allocated size.
 			 * Reallocate VBO. */
-			VBO::uploadData(size, &vertices[0], GL_DYNAMIC_DRAW);
+			VBO::uploadData(size, dataPtr(vertices), GL_DYNAMIC_DRAW);
 			vboSize = size;
 
 			shState->ensureQuadIBO(quadCount);
@@ -94,7 +94,7 @@ struct QuadArray
 		else
 		{
 			/* New data fits in allocated size */
-			VBO::uploadSubData(0, size, &vertices[0]);
+			VBO::uploadSubData(0, size, dataPtr(vertices));
 		}
 
 		VBO::unbind();
diff --git a/src/tileatlasvx.cpp b/src/tileatlasvx.cpp
index 7a5f48c..5af8060 100644
--- a/src/tileatlasvx.cpp
+++ b/src/tileatlasvx.cpp
@@ -265,7 +265,7 @@ createShadowSet()
 
 	/* Fill rects with half opacity black */
 	uint32_t color = (0x80808080 & am);
-	SDL_FillRects(surf, &rects[0], rects.size(), color);
+	SDL_FillRects(surf, dataPtr(rects), rects.size(), color);
 
 	return surf;
 }
diff --git a/src/tilemap.cpp b/src/tilemap.cpp
index 9878275..ac50c70 100644
--- a/src/tilemap.cpp
+++ b/src/tilemap.cpp
@@ -766,7 +766,7 @@ struct TilemapPrivate
 		VBO::bind(tiles.vbo);
 		VBO::allocEmpty(quadDataSize(quadCount));
 
-		VBO::uploadSubData(0, quadDataSize(groundQuadCount), &groundVert[0]);
+		VBO::uploadSubData(0, quadDataSize(groundQuadCount), dataPtr(groundVert));
 
 		for (size_t i = 0; i < zlayersMax; ++i)
 		{
@@ -774,7 +774,7 @@ struct TilemapPrivate
 				continue;
 
 			VBO::uploadSubData(quadDataSize(zlayerBases[i]),
-			                   quadDataSize(zlayerSize(i)), &zlayerVert[i][0]);
+			                   quadDataSize(zlayerSize(i)), dataPtr(zlayerVert[i]));
 		}
 
 		VBO::unbind();
@@ -855,7 +855,7 @@ struct TilemapPrivate
 			return;
 
 		VBO::bind(flash.vbo);
-		VBO::uploadData(sizeof(CVertex) * vertices.size(), &vertices[0]);
+		VBO::uploadData(sizeof(CVertex) * vertices.size(), dataPtr(vertices));
 		VBO::unbind();
 
 		/* Ensure global IBO size */
diff --git a/src/tilemapvx.cpp b/src/tilemapvx.cpp
index bbd925d..d45e82d 100644
--- a/src/tilemapvx.cpp
+++ b/src/tilemapvx.cpp
@@ -236,8 +236,8 @@ struct TilemapVXPrivate : public ViewportElement, TileAtlasVX::Reader
 			allocQuads = totalQuads;
 		}
 
-		VBO::uploadSubData(0, quadBytes(groundQuads), &groundVert[0]);
-		VBO::uploadSubData(quadBytes(groundQuads), quadBytes(aboveQuads), &aboveVert[0]);
+		VBO::uploadSubData(0, quadBytes(groundQuads), dataPtr(groundVert));
+		VBO::uploadSubData(quadBytes(groundQuads), quadBytes(aboveQuads), dataPtr(aboveVert));
 
 		VBO::unbind();
 
diff --git a/src/util.h b/src/util.h
index 8009a26..2a48ef4 100644
--- a/src/util.h
+++ b/src/util.h
@@ -25,6 +25,7 @@
 #include <stdio.h>
 #include <string>
 #include <algorithm>
+#include <vector>
 
 static inline int
 wrapRange(int value, int min, int max)
@@ -101,6 +102,18 @@ inline bool contains(const C &c, const V &v)
 	return std::find(c.begin(), c.end(), v) != c.end();
 }
 
+template<typename C>
+inline const C *dataPtr(const std::vector<C> &v)
+{
+	return v.empty() ? (C*)0 : &v[0];
+}
+
+template<typename C>
+inline C *dataPtr(std::vector<C> &v)
+{
+	return v.empty() ? (C*)0 : &v[0];
+}
+
 #define ARRAY_SIZE(obj) (sizeof(obj) / sizeof((obj)[0]))
 
 #define elementsN(obj) const size_t obj##N = ARRAY_SIZE(obj)
diff --git a/src/windowvx.cpp b/src/windowvx.cpp
index cc6d193..0b01a6e 100644
--- a/src/windowvx.cpp
+++ b/src/windowvx.cpp
@@ -374,7 +374,7 @@ struct WindowVXPrivate
 
 		base.vert.resize(count);
 
-		Vertex *vert = &base.vert.vertices[0];
+		Vertex *vert = dataPtr(base.vert.vertices);
 		size_t i = 0;
 
 		/* Stretched background */
@@ -518,7 +518,7 @@ struct WindowVXPrivate
 		};
 
 		size_t i = 0;
-		Vertex *vert = &ctrlVert.vertices[0];
+		Vertex *vert = dataPtr(ctrlVert.vertices);
 
 		if (!nullOrDisposed(contents) && arrowsVisible)
 		{
@@ -600,7 +600,7 @@ struct WindowVXPrivate
 			quads += 1;
 
 		cursorVert.resize(quads);
-		Vertex *vert = &cursorVert.vertices[0];
+		Vertex *vert = dataPtr(cursorVert.vertices);
 		size_t i = 0;
 
 		i += Quad::setTexPosRect(&vert[i*4], src.corners.tl, cornerPos.tl);