From a220e7c42271fa88d9ff92427c65894408d31e0e Mon Sep 17 00:00:00 2001
From: Derek Schuff <[EMAIL REDACTED]>
Date: Thu, 1 May 2025 23:19:50 +0000
Subject: [PATCH] Port #12581 to SDL2
This fixes undefined behavior resulting from adding offsets to nullptr.
---
src/render/opengles2/SDL_render_gles2.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
index f5f221c46b607..e8b6f206e3cab 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -975,8 +975,8 @@ static int SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, co
}
if (texture) {
- SDL_Vertex *verts = (SDL_Vertex *)(((Uint8 *)vertices) + cmd->data.draw.first);
- data->glVertexAttribPointer(GLES2_ATTRIBUTE_TEXCOORD, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *)&verts->tex_coord);
+ uintptr_t base = (uintptr_t)vertices + cmd->data.draw.first; // address of first vertex, or base offset when using VBOs.
+ data->glVertexAttribPointer(GLES2_ATTRIBUTE_TEXCOORD, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *)(base + offsetof(SDL_Vertex, tex_coord)));
}
if (GLES2_SelectProgram(data, imgsrc, texture ? texture->w : 0, texture ? texture->h : 0) < 0) {
@@ -1009,9 +1009,9 @@ static int SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, co
/* all drawing commands use this */
{
- SDL_VertexSolid *verts = (SDL_VertexSolid *)(((Uint8 *)vertices) + cmd->data.draw.first);
- data->glVertexAttribPointer(GLES2_ATTRIBUTE_POSITION, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *)&verts->position);
- data->glVertexAttribPointer(GLES2_ATTRIBUTE_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE /* Normalized */, stride, (const GLvoid *)&verts->color);
+ uintptr_t base = (uintptr_t)vertices + cmd->data.draw.first; // address of first vertex, or base offset when using VBOs.
+ data->glVertexAttribPointer(GLES2_ATTRIBUTE_POSITION, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *)(base + offsetof(SDL_VertexSolid, position)));
+ data->glVertexAttribPointer(GLES2_ATTRIBUTE_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE /* Normalized */, stride, (const GLvoid *)(base + offsetof(SDL_VertexSolid, color)));
}
return 0;
@@ -1200,7 +1200,8 @@ static int GLES2_RunCommandQueue(SDL_Renderer *renderer, SDL_RenderCommand *cmd,
if (data->current_vertex_buffer >= SDL_arraysize(data->vertex_buffers)) {
data->current_vertex_buffer = 0;
}
- vertices = NULL; /* attrib pointers will be offsets into the VBO. */
+ // attrib pointers will be offsets into the VBO.
+ vertices = (void *)(uintptr_t)0; // must be the exact value 0, not NULL (the representation of NULL is not guaranteed to be 0).
#endif
while (cmd) {