Compilation of SDL3 with importC failes (missing __builtin's)

[MikeShah]

Description

I've tried building the C based Simple Directmedia Layer (SDL) library (https://libsdl.org/) for version 3.2.0 using importC. It almost works, but is missing a few of the built-in functions otherwise for compiling the library.

These appear to be the built-ins: https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html

Short term suggested action are to add the built-ins to the importc.h or wherever otherwise appropriate. Users can otherwise do #define __builtin_mul_overflow(a,b,ret) 0 to otherwise get the importC compiler to work (The application appears to work, but the behavior would be broken for overflows).

Longer term suggested action, would be to use SDL3 as a test-suite for importC. Generally SDL3 is used by lots of game/multimedia developers, so if we can make the setup process as simple as including the header, that would be a big win for D for game developers.

Setup

Provided below is a test application and the command line I have used

• Tested on Ubuntu Linux 24.04
• Compiler: DMD64 D Compiler v2.111.0
• dmd app.d -L-lSDL3 -P-I/home/mike/Downloads/SDL3/include/SDL3/ sdl.c

---

Sample application

Sample application for testing purposes

// @file: app.d
import std.stdio;
import sdl;

void main(){
  // Flags for subsystems we want to initialize
	SDL_InitFlags flags = SDL_INIT_VIDEO | SDL_INIT_EVENTS;

  // Initialize SDL
	if(SDL_Init(flags)){
		writeln("SDL was initialized");
	}else{
		writeln("Failed to initialize subsystems");
    return;
	}

  // Create our window
  SDL_Window* window = SDL_CreateWindow("DSDL3 window w/ manual binding - no dub packages",
                                        320,240,0);

  // 3 second delay (3000 ms)
  SDL_Delay(3000);

  // Destroy window
  SDL_DestroyWindow(window);

	writeln("Shutting down initialized subsystems");
	SDL_Quit();
}

/// @file: sdl.c
//#define __builtin_mul_overflow(a,b,ret) 0
//#define __builtin_add_overflow(a,b,ret) 0
//#define __builtin_clz(x) 0
#include <SDL.h>

[felixf4xu]

For the first 2 builtin functions, SDL3 uses them but with some compiler switch like SDL_HAS_BUILTIN:

#if SDL_HAS_BUILTIN(__builtin_mul_overflow)
/* This needs to be wrapped in an inline rather than being a direct #define,
 * because __builtin_mul_overflow() is type-generic, but we want to be
 * consistent about interpreting a and b as size_t. */
SDL_FORCE_INLINE bool SDL_size_mul_check_overflow_builtin(size_t a, size_t b, size_t *ret)
{
    return (__builtin_mul_overflow(a, b, ret) == 0);
}
#define SDL_size_mul_check_overflow(a, b, ret) SDL_size_mul_check_overflow_builtin(a, b, ret)
#endif

and

#ifdef __has_builtin
#define SDL_HAS_BUILTIN(x) __has_builtin(x)
#else
#define SDL_HAS_BUILTIN(x) 0
#endif

So if __has_builtin is not defined, it will not be an issue.

Checked with the commit history,

__has_builtin is undefined by commit 23e2b3c94378848f80b4936c3f471c4ba844f9cc, but the undefining code is removed (so it's defined again) in commit b8b51f0db26367a732687e3c1b674f31ec19f2ff. So reverting commit of b8b51f0db26367a732687e3c1b674f31ec19f2ff might be a solution to the issue

(only the first 2 functions, the issue of the 3rd function is not fixed by that).

[thewilsonator]

cc @ibuclaw