[gentoo-alt] {Spam?} Why is ld-wrapper forcing -macosx_version_min?

[Michael Weiser]

Hi,

does anyone remember, why the prefix ld wrapper from
toolchain-prefix-wrapper-0.3.1723 forces the -macosx_version_min onto
the ld command line?

It breaks cross-compilation for e.g. armv6 using our shiny new
binutils-apple-6.1 and a multitarget clang:

michael@osx1010:~ # which clang
/Users/michael/nobak/gentoo/usr/bin/clang
michael@osx1010:~ # clang -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk -arch armv7 -o t t.c
ld: building for MacOSX, but linking against dylib built for iOS Simulator file '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk/usr/lib/libSystem.dylib' for architecture armv7
x86_64-apple-darwin14-clang-3.5.1: error: linker command failed with exit code 1 (use -v to see invocation)

Xcode clang accepts the same command line nicely and produces arm
output:

michael@osx1010:~ # which clang
/usr/bin/clang
michael@osx1010:~ # clang -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk -arch armv7 -o t t.c
michael@osx1010:~ # file t
t: Mach-O executable arm

After removing the parameter override from the ld wrapper using the
attached patch and changed ebuild, all is well:

michael@osx1010:~ # which clang
/Users/michael/nobak/gentoo/usr/bin/clang
michael@osx1010:~ # clang -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk -arch armv7 -o t t.c
michael@osx1010:~ # file t
t: Mach-O arm_v7 executable

Also, I do think the override is not neccessary (at least any more)
because the way ld64 is configured by binutils-apple now it will pick up
its default deployment target from the ebuild environment. And that's
explicitly set by all the prefix darwin profiles. 

michael@osx1010:~ # ld -v
@(#)PROGRAM:ld  PROJECT:ld64-241.9 (Gentoo binutils-apple-6.1)
configured to support archs: i386 x86_64 x86_64h armv6 armv7 armv7s armv7m arm64
[...]
ld: warning: -arch not specified
ld: warning: -macosx_version_min not specified, assuming 10.9
ld: no object files specified for inferred architecture x86_64

Relevant code from ld64's Option.cpp:

switch ( type ) {
         case CPU_TYPE_I386:
         case CPU_TYPE_X86_64:
                 if ( (fMacVersionMin == ld::macVersionUnset) && (fIOSVersionMin == ld::iOSVersionUnset) && (fOutputKind != Options::kObjectFile) ) {
         #ifdef DEFAULT_MACOSX_MIN_VERSION
                         warning("-macosx_version_min not specified, assuming " DEFAULT_MACOSX_MIN_VERSION);
                         setMacOSXVersionMin(DEFAULT_MACOSX_MIN_VERSION);
         #else
                         warning("-macosx_version_min not specified, assuming 10.6");
                         fMacVersionMin = ld::mac10_6;
         #endif          
                 }
                 break;

So what do we think? Can we drop the option override from the ld
wrapper?
-- 
Micha