Trouble getting 8-bit palette output working with SDL 2.0 - sdl

Question

Here's my code, using SDL 2.0.4 on OSX 10.11.4:
SDL_Surface *output_surface = SDL_CreateRGBSurface(0, width, height, 8, 0, 0, 0, 0);
SDL_Texture *output_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STREAMING, width, height);
SDL_Color c[256];
// Setting each color to red as a test.
for(u8 i = 255; i--;) {
c[i].r = 255;
c[i].g = 0;
c[i].b = 0;
}
SDL_SetPaletteColors(output_surface->format->palette, c, 0, 256);
Then later...
SDL_Rect r = {
.x = 0,
.y = 0,
.w = width,
.h = height
};
// Doesn't fill with red.
SDL_FillRect(output_surface, &r, 4);
SDL_UpdateTexture(output_texture, NULL, output_surface->pixels, output_surface->pitch);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, output_texture, NULL, NULL);
SDL_RenderPresent(renderer);
What I would expect to see is the full window all red but I'm getting something entirely different. Changing the color number passed to SDL_FillRect shows that I'm getting a grayscale palette (0 is black, 255 is white) even though SDL_SetPaletteColors doesn't return an error and i've looped through output_surface->format->palette->colors to verify the palette's been changed.
What am I missing here?
edit: I was asked to post an entire program. Here it is:
int main(int argc, const char *argv[]) {
SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
SDL_Surface *output_surface = NULL;
SDL_Texture *output_texture = NULL;
int width = 640;
int height = 480;
if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER) < 0) return 0;
window = SDL_CreateWindow("Sample", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, 0);
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_ACCELERATED);
output_surface = SDL_CreateRGBSurface(0, width, height, 8, 0, 0, 0, 0);
output_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STREAMING, width, height);
SDL_Color c[256];
for(u8 i = 255; i--;) {
c[i].r = 255;
c[i].g = 0;
c[i].b = 0;
c[i].a = 255;
}
SDL_SetPaletteColors(output_surface->format->palette, c, 0, 255);
SDL_Rect r = {
.x = 0,
.y = 0,
.w = width,
.h = height
};
bool running = true;
while(running) {
SDL_Event event;
while(SDL_PollEvent(&event)) {
switch(event.type){
case SDL_KEYDOWN:
running = false;
break;
}
}
SDL_FillRect(output_surface, &r, 124);
SDL_UpdateTexture(output_texture, NULL, output_surface->pixels, output_surface->pitch);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, output_texture, NULL, NULL);
SDL_RenderPresent(renderer);
}
SDL_FreeSurface(output_surface);
SDL_DestroyTexture(output_texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
Passing 0 to SDL_FillRect is black, 255 is white, and any number in-between is a shade of grey.

Answer 1

Alright, found the solution.
Remove this line:
output_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STREAMING, width, height);
And instead add this line somewhere after the call to SDL_SetPaletteColors or after you change the surfaces' pixels (like in the game loop):
output_texture = SDL_CreateTextureFromSurface(renderer, output_surface);