SDL2_Image: Weird cross compile error on macOS arm64 building for x86_64

[DominusExult]

When I'm cross compiling for x86_64 on an Apple Silicon macOS I'm getting these errors:

In file included from /opt/x86_64/include/SDL2/SDL_cpuinfo.h:119:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/17/include/immintrin.h:14:2: error: "This header is only meant to be used on x86 and x64 architecture"
   14 | #error "This header is only meant to be used on x86 and x64 architecture"
      |  ^
In file included from /Users/Dominus/Code/Uni/SDL2_image-2.8.8/src/IMG_bmp.c:33:
In file included from /Users/Dominus/Code/Uni/SDL2_image-2.8.8/include/SDL_image.h:32:
In file included from /opt/x86_64/include/SDL2/SDL.h:37:
In file included from /opt/x86_64/include/SDL2/SDL_cpuinfo.h:119:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/17/include/immintrin.h:17:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/17/include/x86gprintrin.h:14:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/17/include/hresetintrin.h:42:27: error: invalid input constraint 'a' in asm

and more and more.
This is puzzling me as I normally do not have problems cross compiling libraries and it happens both by using autotools and cmake.

Autotools environment:

OPT=' -O2 -m64 '
SDK=' -isysroot /opt/SDKs/MacOSX14.5.sdk -mmacosx-version-min=10.12'
export MACOSX_DEPLOYMENT_TARGET=10.12
export PATH=/opt/x86_64/bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin
export CC="/usr/bin/clang -arch x86_64"
export CXX="/usr/bin/clang++ -arch x86_64"
export CPPFLAGS='-I/opt/x86_64/include '$SDK
export CFLAGS='-I/opt/x86_64/include '$SDK' '$OPT
export CXXFLAGS='-I/opt/x86_64/include '$SDK' '$OPT
export LDFLAGS='-L/opt/x86_64/lib '$SDK' '$OPT

Cmake toolchain file:

SET(CMAKE_FIND_ROOT_PATH "/opt/x86_64; /opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_SYSROOT "/opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_DEPLOYMENT_TARGET "10.11" CACHE STRING "Minimum OS X deployment version")
SET(CMAKE_C_FLAGS "-arch x86_64")
SET(CMAKE_CXX_FLAGS "-arch x86_64")
SET(CMAKE_INSTALL_PREFIX "/opt/x86_64" CACHE PATH "" FORCE)

Any idea what I'm doing wrong?

[madebr]

What is the failing compile command? (Use the CMake Unix Makefiles or Ninja generator to show a relatively clean verbose build log)

When cross building, you might want to add --build= and --host= gnu triplets to the configure script.
I'd also set CMAKE_SYSTEM_NAME in the toolchain file.

[sezero]

Possibly related: libsdl-org/SDL_mixer#648

[madebr]

Can you also set CMAKE_OSX_ARCHITECTURES in your toolchain file?

[DominusExult]

Possibly related: libsdl-org/SDL_mixer#648

The fix in that issue helped with this issue.

Setting CMAKE_OSX_ARCHITECTURES did help without editing SDL_cpuinfo.h.

On autotools another issue crept up:
ld: warning: ignoring file 'src/.libs/libSDL2_image_la-IMG_ImageIO.o': found architecture 'arm64', required architecture 'x86_64'
Disabling imageio (./configure --disable-imageio) made the build run through.

With Cmake this worked without having to disable imageio

[sezero]

OK, cmake side is good with the corrected toolchain file.

Let's forget about editing SDL_cpuinfo.h:

To clarify: Does autotools build succeed with --disable-imageio without editing SDL_cpuinfo.h?

If it does, try exporting OBJCFLAGS='-I/opt/x86_64/include '$SDK' '$OPT : does it then succeed
wit imageio enabled?

[DominusExult]

With --disable-imageio it builds without a problem (unpatched SDL_cpuinfo.h).

Exporting OBJCFLAGS='-I/opt/x86_64/include '$SDK' '$OPT and not setting --disable-imageio fixes the SDL_cpuinfo.h.
But linking fails again as src/.libs/libSDL2_image_la-IMG_ImageIO.o builds with arch arm64 again (the other *.o files are correctly built as x86_64).

[sezero]

Exporting OBJCFLAGS='-I/opt/x86_64/include '$SDK' '$OPT and not setting --disable-imageio fixes the SDL_cpuinfo.h. But linking fails again as src/.libs/libSDL2_image_la-IMG_ImageIO.o builds with arch arm64 again (the other *.o files are correctly built as x86_64).

Hmph. I guess I missed that OBJC variable should be exported similarly.
E.g. like OBJC="/usr/bin/clang -arch x86_64"
Can you please test again with that? (With SDL_cpuinfo.h not patched and imageio not disabled, of course.)

[DominusExult]

yup, that was the culprit. So I guess user error after all :)

Got to remember to set OBJC as well with the arch, just never stumbled over this before.

[sezero]

OK, great. But remember that several optimization flags may be lost by exporting CFLAGS in autotools, so cmake should be the choice in this macOS case.

However, not sure, but patching SDL_cpuinfo.h might not be a bad idea: What happens if CMAKE_OSX_ARCHITECTURES is set to multiple arches? (That is possible, yes?) And how does cmake's header presence check behave in such a case?

[DominusExult]

However, not sure, but patching SDL_cpuinfo.h might not be a bad idea: What happens if CMAKE_OSX_ARCHITECTURES is set to multiple arches? (That is possible, yes?) And how does cmake's header presence check behave in such a case?

Actually part of the Cmake error at first was that CMAKE_OSX_ARCHITECTURES is set to multiple arches on Apple Silicon. I really struggled with this as I'm not able to set this to one arch in the toolchain, only in the cmake command. I guess that might be a Cmake 4 bug.

[sezero]

@madebr to rescue for those

[madebr]

You can't do set(CMAKE_OSX_ARCHITECTURES "x86_64") in your CMake toolchain? That's weird. What are the actual compile commands and what archs is it trying to build?

What's the behavior of this CMake toolchain file?

set(CMAKE_SYSTEM_NAME "macOS")
set(CMAKE_OSX_ARCHITECTURES "x86_64")
SET(CMAKE_FIND_ROOT_PATH "/opt/x86_64; /opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_SYSROOT "/opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_DEPLOYMENT_TARGET "10.11" CACHE STRING "Minimum OS X deployment version")
SET(CMAKE_INSTALL_PREFIX "/opt/x86_64" CACHE PATH "" FORCE)

Can you share a compile command?

When configuring with -DCMAKE_OSX_ARCHITECTUERS="x86_64;arm64", what are the compile commands then?

[DominusExult]

macos is not a recognized system name and setting CMAKE_OSX_ARCHITECTURES created an empty value in the CMAKE_OSX_ARCHITECTURES:STRING=� line in Cmakecache.txt.
so half working settings are

SET(CMAKE_SYSTEM_NAME "darwin")
SET(CMAKE_OSX_ARCHITECTURES "x86_64" CACHE STRING "")

SET(CMAKE_OSX_ARCHITECTURES "x86_64" CACHE STRING "") without system_name produces this error:

CMake Error at /Applications/CMake.app/Contents/share/cmake-4.0/Modules/CMakeDetermineCompilerABI.cmake:138 (message):
  The C compiler targets architectures:

    "x86_64;arm64"

  but CMAKE_OSX_ARCHITECTURES is

    "x86_64"

Call Stack (most recent call first):
  /Applications/CMake.app/Contents/share/cmake-4.0/Modules/CMakeTestCCompiler.cmake:26 (CMAKE_DETERMINE_COMPILER_ABI)
  CMakeLists.txt:18 (project)

Adding SET(CMAKE_SYSTEM_NAME "darwin") makes Cmake work, and sets CMAKE_OSX_ARCHITECTURES:STRING=x86_64� line in Cmakecache.txt.

But then it mysteriously starts building both arches again, resulting in the cpuinfo error.
And it's very strange, I cannot make it work again without changing SDL_cpuinfo.h and then I get linking errors (of course as it is tries to link the arm64 with my x86_64 SDL2 in /opt/x86_64.
I really don't know why that worked earlier.

Edit: Now I'm really puzzled. I've been using this toolchain to build individual arches for a long time with Cmake, though the last x86_64 build was some months ago. arm64 still builds single but when I try x86_64 it always wants to build multiple arches regardless of which Cmake project I try. And it's not tied to the Cmake version, happens with Cmake 3.31.1 and 4.0.0

[DominusExult]

I'm pretty stupid (or rather doing to many things at once and thus careless. Case solved.

I still had the lingering OBJC="/usr/bin/clang -arch arm64 which set CMAKE_C_COMPILER_ARG1:INTERNAL=-arch arm64 and thus I ran into the multiarches conflicting each other.

So my working toolchain is

SET(CMAKE_OSX_ARCHITECTURES "x86_64" CACHE INTERNAL "")
SET(CMAKE_FIND_ROOT_PATH "/opt/x86_64; /opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_SYSROOT "/opt/SDKs/MacOSX14.5.sdk")
SET(CMAKE_OSX_DEPLOYMENT_TARGET "10.11" CACHE STRING "Minimum OS X deployment version")
SET(CMAKE_C_FLAGS "-arch x86_64")
SET(CMAKE_CXX_FLAGS "-arch x86_64")
SET(CMAKE_INSTALL_PREFIX "/opt/x86_64" CACHE PATH "" FORCE)

This works without changing SDL_cpuinfo.h. However as @sezero suspected, once multiarches are configured SDL_cpuinfo.h breaks.

[sezero]

OK, so CMAKE_OSX_ARCHITECTURES="arm64;x86_64" obviously fails through
SDL_cpuinfo.h, therefore patching is necessary: Patch replicated below for
convenience, and I guess needed in both SDL2 and SDL3. (CC: @slouken )

One question is (as I had already asked above), how does (our) cmake header
presence detection behave with CMAKE_OSX_ARCHITECTURES="arm64;x86_64" ?
(CC: @madebr )

diff --git a/include/SDL_cpuinfo.h b/include/SDL_cpuinfo.h
index e4d7464..7ee75b6 100644
--- a/include/SDL_cpuinfo.h
+++ b/include/SDL_cpuinfo.h
@@ -115,7 +115,8 @@ _m_prefetch(void *__P)
 #include <lasxintrin.h>
 #define __LASX__
 #endif
-#if defined(HAVE_IMMINTRIN_H) && !defined(SDL_DISABLE_IMMINTRIN_H)
+#if defined(HAVE_IMMINTRIN_H) && !defined(SDL_DISABLE_IMMINTRIN_H) && \
+   (defined(__x86_64__) || defined(_M_X64) || defined(__i386__) || defined(_M_IX86))
 #include <immintrin.h>
 #else
 #if defined(__MMX__) && !defined(SDL_DISABLE_MMINTRIN_H)