macOS 15: problems with crates requiring compilation of C sources

[mgrojo]

I've recently got a Mac (macOS 15.7, chip Apple M2) and one of the first things I tried was building some crates 😄

I've encountered many problems, all of them related to compilation of C sources. One of the problems was already seen on the PR of coap_spark https://github.com/alire-project/alire-index/actions/runs/19686448504/job/56539104182?pr=1684

AWS fails with this:

   [C]            process-wrappers.c
   [C]            libc-wrappers.c
   [C]            xxhash.c
In file included from /Users/mgr/.local/share/alire/builds/gnatcoll_25.0.0_d7d84483/065a11a9774015be473fb7ad1ab10cae64e2eddf52cd4fb818b290b0e67fc43b/core/src/os/unix/process-wrappers.c:26:
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:83:8: error: unknown type name 'FILE'
   83 | extern FILE *__stdinp;
      |        ^~~~
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:81:1: note: 'FILE' is defined in header '<stdio.h>'; this is probably fixable by adding '#include <stdio.h>'
   80 | #include <sys/_types/_seek_set.h>
  +++ |+#include <stdio.h>
   81 | 
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:84:8: error: unknown type name 'FILE'
   84 | extern FILE *__stdoutp;
      |        ^~~~

[...]

/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:403:21: note: 'FILE' is defined in header '<stdio.h>'; this is probably fixable by adding '#include <stdio.h>'
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:410:1: error: unknown type name 'FILE'
  410 | FILE    *funopen(const void *,
      | ^~~~
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:410:1: note: 'FILE' is defined in header '<stdio.h>'; this is probably fixable by adding '#include <stdio.h>'
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:413:18: error: unknown type name 'fpos_t'
  413 |                  fpos_t (* _Nullable)(void *, fpos_t, int),
      |                  ^~~~~~
/Users/mgr/.local/share/alire/toolchains/gnat_native_14.1.3_63c4df79/lib/gcc/aarch64-apple-darwin23.5.0/14.1.0/include-fixed/stdio.h:413:18: note: 'fpos_t' is defined in header '<stdio.h>'; this is probably fixable by adding '#include <stdio.h>'

   compilation of libc-wrappers.c failed
   compilation of process-wrappers.c failed

gprbuild: *** compilation phase failed
error: Command ["gprbuild", "-s", "-j0", "-p", "-P", "/Users/mgr/src/alire/aws_25.2.0_bb26af84/aws.gpr"] exited with code 4

warn: aws=25.2.0 successfully retrieved but its build failed.
Dependencies were solved as follows:                      

   +📦 gnat     14.1.3 (new,gnat_native,binary)
   +   gnatcoll 25.0.0 (new)
   +   libgpr   25.0.0 (new,indirect)
   +📦 make     4.4.1  (new,system package)
   +📦 openssl  3.6.0  (new,system package)
   +   xmlada   25.0.0 (new)
error: Build ended with errors

And gtkada with this error:

ⓘ Deploying gtkada=25.0.1...                                             
       -=O=-              #             #              #                #                                                                                                                                                                                       
ⓘ Running post-fetch actions for gtkada=25.0.1...                        
checking build system type... arm-apple-darwin24.6.0
checking host system type... arm-apple-darwin24.6.0
checking target system type... arm-apple-darwin24.6.0
checking for pkg-config... /opt/homebrew/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... configure: error: in `/Users/mgr/src/alire/gtkada_25.0.1_d3787772':
configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details
warn: Execution failed for action: Post_Fetch run: bash -c PATH=${DISTRIB_ROOT}/mingw64/bin:${PATH} ./configure (from ${CRATE_ROOT}/.)
warn: Exit code: 1
warn: Action output not captured, check it above.

warn: gtkada=25.0.1 successfully retrieved but its build failed.
Dependencies were solved as follows:                         

   +📦 libgtk3    3.24.51 (new,system package)
   +📦 make       4.4.1   (new,system package)
   +📦 pkg_config 2.5.1   (new,system package)
error: Build ended with errors

The problem is that GCC is overly sensitive to exact SDK version used to build it

I first tried changing SDKROOT to the various values available in /Library/Developer/CommandLineTools/SDKs/ without success.

I then tried changing the default toolchain to gnat_native=13.2.2, gnat_native=14.2.1 and finally gnat_native=15.1.2, which finally worked. So with this macOS version, the only valid GNAT when compiling C sources seems to be GNAT 15.

Does someone know of a bester solution?