From 14deef997cf461b40cfd3e340e98622421035022 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Carl=20=C3=85stholm?= 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 ac06d7d04d..88ade53624 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) {