From 14deef997cf461b40cfd3e340e98622421035022 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carl=20=C3=85stholm?= <[EMAIL REDACTED]>
Date: Wed, 19 Mar 2025 01:29:22 +0100
Subject: [PATCH] emscripten: Fix undefined behavior in opengles2 renderer
---
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 ac06d7d04d3a0..88ade536240a4 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -1022,8 +1022,8 @@ static bool SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, c
}
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)));
}
SDL_Colorspace colorspace = texture ? texture->colorspace : SDL_COLORSPACE_SRGB;
@@ -1057,9 +1057,9 @@ static bool SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, c
// 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_FLOAT, 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_FLOAT, GL_TRUE /* Normalized */, stride, (const GLvoid *)(base + offsetof(SDL_VertexSolid, color)));
}
return true;
@@ -1375,7 +1375,8 @@ static bool 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) {