stage2: add --sysroot link option #9202
Conversation
| if (cross_target.isNativeOs() and (system_libs.items.len != 0 or want_native_include_dirs)) { | ||
| if (sysroot == null and cross_target.isNativeOs() and | ||
| (system_libs.items.len != 0 or want_native_include_dirs)) | ||
| { |
There was a problem hiding this comment.
@kubkon am I correct that skipping this logic makes sense if an explicit sysroot is provided?
Also, I've just realized that I should add support for this new flag in src/link/MachO.zig as well, or at least a error instead of silent failure. Does zig ld support this feature yet?
There was a problem hiding this comment.
You should and zig ld supports syslibroot.
There was a problem hiding this comment.
Also, I believe you're correct here. If the user explicitly specifies the sysroot, we should just take it rather than infer it automatically.
There was a problem hiding this comment.
We do have a concept of syslibroot in the linking stage as a flag, but with clang this usually is passed using -Wl,-syslibroot, and I'm not sure how sysroot should be remapped to it. Anyway, we use it with zig ld like so:
Line 724 in d1f99ea
There was a problem hiding this comment.
Are the semantics of syslibroot the same as that of --sysroot for lld? lld and gnu ld understand --sysroot to be the root directory in which to look for both shared object and include files.
There's also -isysroot which only sets the root directory in which to look for include files, overriding --sysroot for them. I don't have a use-case for exposing a Zig flag to do that so I've left it off for now.
There was a problem hiding this comment.
I think that's also true for Apple's ld64:
❯ clang --sysroot $(xcrun --show-sdk-path) hello.cpp -lc++ -v
Apple clang version 12.0.5 (clang-1205.0.22.9)
Target: arm64-apple-darwin20.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple arm64-apple-macosx11.0.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -Werror=implicit-function-declaration -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name hello.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=non-leaf -fno-strict-return -fno-rounding-math -munwind-tables -target-sdk-version=11.3 -fvisibility-inlines-hidden-static-local-var -target-cpu apple-a12 -target-feature +v8.3a -target-feature +fp-armv8 -target-feature +neon -target-feature +crc -target-feature +crypto -target-feature +fullfp16 -target-feature +ras -target-feature +lse -target-feature +rdm -target-feature +rcpc -target-feature +zcm -target-feature +zcz -target-feature +sha2 -target-feature +aes -target-abi darwinpcs -fallow-half-arguments-and-returns -debugger-tuning=lldb -target-linker-version 650.9 -v -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.5 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -stdlib=libc++ -internal-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1 -internal-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/local/include -internal-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.5/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Wno-reorder-init-list -Wno-implicit-int-float-conversion -Wno-c99-designator -Wno-final-dtor-non-final-class -Wno-extra-semi-stmt -Wno-misleading-indentation -Wno-quoted-include-in-framework-header -Wno-implicit-fallthrough -Wno-enum-enum-conversion -Wno-enum-float-conversion -Wno-elaborated-enum-base -fdeprecated-macro -fdebug-compilation-dir /Users/kubkon/dev/zig/examples -ferror-limit 19 -stack-protector 1 -fstack-check -mdarwin-stkchk-strong-link -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fmax-type-align=16 -fcommon -fcolor-diagnostics -clang-vendor-feature=+disableNonDependentMemberExprInCurrentInstantiation -fno-odr-hash-protocols -mllvm -disable-aligned-alloc-awareness=1 -o /var/folders/ym/hxsqmxds3mqbxxrk4l3jl31h0000gn/T/hello-5c1855.o -x c++ hello.cpp
clang -cc1 version 12.0.5 (clang-1205.0.22.9) default target arm64-apple-darwin20.6.0
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.5/include
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)
End of search list.
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -lto_library /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch arm64 -platform_version macos 11.0.0 11.3 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -o a.out /var/folders/ym/hxsqmxds3mqbxxrk4l3jl31h0000gn/T/hello-5c1855.o -lc++ -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.5/lib/darwin/libclang_rt.osx.a
As you can see, -syslibroot was set to the sysroot value which is exactly what we want here as well.
|
@ifreund do you need any assistance with this PR? Turns out we need this to support linking frameworks when cross-compiling to macOS. |
@kubkon I just got busy with other things, though I would certainly appreciate another round of review wrt the darwin side of things. I opted to replace "syslibroot" with "sysroot" in non darwin-specific code as this matches the zig command line option and matches the term I expect more users to be familiar with from using C compilers. Glad that this will solve problems for cross compiling to macOS as well! |
src/Compilation.zig
Outdated
| const sysroot = blk: { | ||
| if (options.sysroot) |sysroot| { | ||
| break :blk sysroot; | ||
| } else if (build_options.have_llvm and comptime std.Target.current.isDarwin() and |
There was a problem hiding this comment.
You'll need to either split the check into two so that build_options.have_llvm and comptime std.Target.current.isDarwin() is evaluated in compile-time, or remove the comptime altogether. use_lld and options.target.isDarwin() are only runtime-known.
There was a problem hiding this comment.
Ah I see. On looking at this again I realize that as an unintended side-effect of my changes the system linker hack will not work if --sysroot is passed. I'll look for a way to fix both of these things without duplicating logic.
There was a problem hiding this comment.
Actually, given that we are close to removing system linker hack altogether, I'm fine with not having it on with explicit --sysroot. Thoughts? @andrewrk care to weigh in?
There was a problem hiding this comment.
There is actually one major feature that's still missing, creation of dylibs, but apart from that, zig ld is more than capable.
There was a problem hiding this comment.
I've force-pushed again and revised this code to make the system linker hack compatible with --sysroot and hopefully fix the compile error.
This feature is necessary for cross-compiling code that dynamically links system libraries, at least with the current feature set of lld.
This feature is necessary for cross-compiling code that dynamically
links system libraries, at least with the current feature set of lld.
Example usage to integrate with void linux's xbps-src cross compilation and packaging tool: void-linux/void-packages#29288