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emscripten: Fix undefined behavior in opengles2 renderer #12581

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Merged
merged 1 commit into from
Mar 19, 2025
Merged

emscripten: Fix undefined behavior in opengles2 renderer #12581

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13 changes: 7 additions & 6 deletions src/render/opengles2/SDL_render_gles2.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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) {
Expand Down
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