gh-128156: Guard use of ffi_type_complex_double on macOS system libffi

[encukou]

formattable.fmt{C,E,F} now have a runtime guard (if USING_APPLE_OS_LIBFFI).
The list of type codes (previously SIMPLE_TYPE_CHARS) is now generated at runtime.

• Issue: Use of ffi_type_complex_double is unguarded #128156

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📚 Documentation preview 📚: https://cpython-previews--128680.org.readthedocs.build/

[skirpichev]

Looks good, but we need some feedback from MacOS experts.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @encukou for commit e8b0992 🤖

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[ned-deily]

cc: @ronaldoussoren @python/macos-team

[ned-deily]

LGTM. I verified that with the PR we could now build and install cpython on the current macOS 15.2 using MACOSX_DEPLOYMENT_TARGET=10.14 and then also install and execute the same binaries on a macOS 10.14.x system. As expected, on 15.2 the three complex types were available and on 10.14, they were not. And test_ctypes ran without errors on both systems. Nice work, @encukou !

[encukou]

Thank you for the thorough review!

[picnixz]

Not sure if it's my system or not but I'm unable to compile :(

Infileincludedfrom ./Modules/_ctypes/callproc.c:87:0: ./Modules/_ctypes/ctypes.h:12:72: error: missingbinaryoperatorbeforetoken"("# ifUSING_APPLE_OS_LIBFFI&& defined(__has_builtin) &&__has_builtin(__builtin_available) 

Other uses of __has_builtin are guarded by #if defined(__APPLE__):

#if defined(__APPLE__) && defined(__has_builtin) 

I'm using OpenSUSE and gcc 7.5

[picnixz]

I think we should do the following:

diff --git a/Modules/_ctypes/ctypes.h b/Modules/_ctypes/ctypes.h index 1330754a7e0..dc079f2441b 100644 --- a/Modules/_ctypes/ctypes.h+++ b/Modules/_ctypes/ctypes.h@@ -9,8 +9,12 @@ // For Apple's libffi, this must be determined at runtime (see gh-128156). #if defined(Py_HAVE_C_COMPLEX) && defined(Py_FFI_SUPPORT_C_COMPLEX) # include "../_complex.h" // complex -# if USING_APPLE_OS_LIBFFI && defined(__has_builtin) && __has_builtin(__builtin_available)-# define Py_FFI_COMPLEX_AVAILABLE __builtin_available(macOS 10.15, *)+# ifdef __has_builtin+# if USING_APPLE_OS_LIBFFI && __has_builtin(__builtin_available)+# define Py_FFI_COMPLEX_AVAILABLE __builtin_available(macOS 10.15, *)+# else+# define Py_FFI_COMPLEX_AVAILABLE 1+# endif # else # define Py_FFI_COMPLEX_AVAILABLE 1 # endif

This is also what's recommended by https://gcc.gnu.org/onlinedocs/cpp/_005f_005fhas_005fbuiltin.html.

cc @encukou@zanieb@ned-deily

[encukou]

Isn't `#if defined(__has_builtin)` equivalent to `#ifdef __has_builtin`?

[picnixz]

Yes, but somehow this doesn't work so I don't know :( (I'll check tomorrow again but the current code doesn't compile on my side)

[encukou]

I'd be interested to know what compiler, OS and configure settings you're using.

[picnixz]

I'm using gcc 7.5.0, my OS is openSUSE 15.5 and I used ./configure --with-pydebug. I can recheck tomorrow (I temporarily fixed this by defining __has_builtin).

[picnixz]

See #129141 for the relevant issue.