Issue with assert in file generated by translate-c (regression - zig 0.17+870-ish)

yinameah · June 20, 2026, 1:07pm

I started having this issue while building SDL3 for dvui :

.zig-cache/o/5a5aeab7c329fb1a07420d083f7f609d/sdl3-c.zig:3857:49: error: null pointer casted to type '*sdl3-c.union_SDL_Event'
    if (!(@sizeOf(SDL_Event) == @sizeOf(@TypeOf(@as([*c]SDL_Event, null).*.padding)))) @compileError("static assertion failed \"sizeof(SDL_Event) == sizeof((SDL_
static_cast(SDL_Event *, NULL))->padding)\"");

This check seems to be a direct translation of this line :

github.com/Yinameah/SDL

include/SDL3/SDL_events.h

2b45a2ba7


      
                 So... we'll add padding to force the size to be the same for both.
          
                 On architectures where pointers are 16 bytes, this needs rounding up to
                 the next multiple of 16, 64, and on architectures where pointers are
                 even larger the size of SDL_UserEvent will dominate as being 3 pointers.
              */
              Uint8 padding[128];
          } SDL_Event;
          
          /* Make sure we haven't broken binary compatibility */
          SDL_COMPILE_TIME_ASSERT(SDL_Event, sizeof(SDL_Event) == sizeof((SDL_static_cast(SDL_Event *, NULL))->padding));
          
          
          /* Function prototypes */
          
          /**
           * Pump the event loop, gathering events from the input devices.
           *
           * This function updates the event queue and internal input device state.
           *
           * SDL_PumpEvents() gathers all the pending input information from devices and

I’m not sure what is the exact commit introducing this but it was still working fine with 0.17.0-dev.864+3deb86baf and started to show up for me in 0.17.0-dev.889+e6be5cfe3

Note that it seems the check was already translated with the working (dev.864) compiler but the compileError was not triggered.

Anybody familiar with this stuff ?

Justus2308 · June 20, 2026, 1:38pm

this was a temporary regression and has been fixed on master:
https://codeberg.org/ziglang/zig/pulls/35851

yinameah · June 20, 2026, 2:18pm

Wonderful. Thanks. Bad timing on my side. Should have waited a couple of extra days