Cannot build SDL Ada Bindings on OSX Sonoma because of error: missing binary operator before token "("

I am trying to write a small game using ADA (via Alire and gnat_native toolchain) and SDL2 on my OSX Sonoma 14.4.1.

For Ada I am using Alire and from what I can see I have latest gnat native version (according to https://alire.ada.dev/crates/gnat_native):

> alr --version
alr 2.0.1

> alr toolchain
CRATE VERSION STATUS NOTES
gprbuild 22.0.1 Default
gnat_native 13.2.2 Default

I added the SDL bindings to my project with the following command alr with sdlada but when I try building it with alr build on my Mac I get the following error:

> alr build
ⓘ Running pre-build actions for sdlada=2.5.20...                               
mkdir -p gen/src/
ⓘ Building tictactoe=0.1.0-dev/tictactoe.gpr...
Compile
   [C]            version_ttf.c
   [C]            version_images.c
   [C]            version.c
In file included from /usr/local/include/SDL2/SDL_platform.h:76,
                 from /usr/local/include/SDL2/SDL_config.h:33,
                 from /usr/local/include/SDL2/SDL_stdinc.h:31,
                 from /usr/local/include/SDL2/SDL_main.h:25,
                 from /usr/local/include/SDL2/SDL.h:32,
                 from /Users/stefano/.local/share/alire/builds/sdlada_2.5.20_cd53c280/42d3242441b923cdce0d399fdf8d3b6b1a75d0874241c5467499cc92113894c2/src/version.c:4:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/TargetConditionals.h:140:50: error: missing binary operator before token "("
  140 | #if !defined(__has_extension) || !__has_extension(define_target_os_macros)
      |                                                  ^
In file included from /usr/local/include/SDL2/SDL_platform.h:76,
                 from /usr/local/include/SDL2/SDL_config.h:33,
                 from /usr/local/include/SDL2/SDL_stdinc.h:31,
                 from /usr/local/include/SDL2/SDL_main.h:25,
                 from /usr/local/include/SDL2/SDL.h:32,
                 from /usr/local/include/SDL2/SDL_image.h:32,
                 from /Users/stefano/.local/share/alire/builds/sdlada_2.5.20_cd53c280/42d3242441b923cdce0d399fdf8d3b6b1a75d0874241c5467499cc92113894c2/src/image/version_images.c:4:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/TargetConditionals.h:140:50: error: missing binary operator before token "("
  140 | #if !defined(__has_extension) || !__has_extension(define_target_os_macros)
      |                                                  ^
In file included from /usr/local/include/SDL2/SDL_platform.h:76,
                 from /usr/local/include/SDL2/SDL_config.h:33,
                 from /usr/local/include/SDL2/SDL_stdinc.h:31,
                 from /usr/local/include/SDL2/SDL_main.h:25,
                 from /usr/local/include/SDL2/SDL.h:32,
                 from /usr/local/include/SDL2/SDL_ttf.h:39,
                 from /Users/stefano/.local/share/alire/builds/sdlada_2.5.20_cd53c280/42d3242441b923cdce0d399fdf8d3b6b1a75d0874241c5467499cc92113894c2/src/ttf/version_ttf.c:4:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/TargetConditionals.h:140:50: error: missing binary operator before token "("
  140 | #if !defined(__has_extension) || !__has_extension(define_target_os_macros)
      |                                                  ^

   compilation of version.c failed
   compilation of version_images.c failed
   compilation of version_ttf.c failed

gprbuild: *** compilation phase failed

Which seems to be an error raised in the OSX SDK libraries themselves.

I think this SDL installation works because I have been using it a different project written in C++ (C++20) and compiled via CMake/Clang.

Taking inspiration from this post https://github.com/orgs/Homebrew/discussions/5195 it seems that the issue is because the pre-processor that is being used (which I am not sure how to find out which one is it) does not support __has_extension which is a C++17 feature.

Is there any way that I can instruct Alire/toolchain/gnat_native to use a different C++ compiler supporting this? Or force the compiler used by alr build to use the C++17 standard? Or is there a way to use a different tool-chain that can support this (possibly via Alire)? Or a way to just let the SDL ADA bindings to the static or dynamic compiled I already have installed on my machine (via home-brew)?

Solution

That was my question on the Homebrew site! I thought it looked familiar!

The following file locations are Alire 2.0-specific, earlier Alire versions are organised differently.

Under ~.local/share/alire, you’ll find 3 directories:

toolchains contains .. toolchain releases.
releases contains downloaded releases of crates.
builds contains cached builds of crates using specific tools.

Now you have an (unsuccessful) build, the last will have been populated, so to proceed from there,

navigate to the latest sdlada; I have sdlada_2.5.20_cd53c280.
Inside this there’s at least one long hash, corresponding to the tool used. I only have one; cd into it (if there’s more than one, you could use the latest, I suppose).
edit build/gnat/sdlada.gpr like this:

@@ -36,6 +36,7 @@ library project SDLAda is
    for Library_Kind use "static";
 
    package Compiler is
+      for Driver ("C") use "clang";
       Common_Switches := ("-ffunction-sections", "-fdata-sections");
       C_Switches      := ();
       Ada_Switches    := ("-gnat2012", "-gnata", "-gnato", "-gnatwa",

This is very much a workround! The proper resolution needs to be done at source. Would you like to post an issue on sdlada’s Github repo, or shall I do it?