Embedded: pass -nostdlib for Embedded Wasm
#1534
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Currently when linking with `swiftc` for `-unknown-none-` triples, it attempts to link `swiftrt.o` runtime file, which is currently not needed and is not present for these triples. We should avoid linking it in these cases.
Embedded Wasm binaries don't have compatible compiler-rt or C stdlib available, turn it off by default.
MaxDesiatov
added
bug
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@kubamracek @rauhul it's unclear to me if we want to pass |
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It makes some sense to make -nostdlib as default for Embedded + WebAssembly targets.
But the problems here are:
- Embedded feature and
-nostdlibare orthogonal concepts and Embedded application are not prohibited from linking libc and compiler-rt. - There is no way to tell clang linker driver to re-enable stdlib link.
So at least, we should have an option not to add -nostdlib even with Embedded + WebAssemby targets. Or given that Embedded is for expert feature, we can ask developers to add -Xclang-linker -nostdlib for their driver invocations.
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I guess the correct file you intended to modify is Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift. GenericUnixToolchain is not used for wasm targets.
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WebAssemblyToolchain is not used for Embedded Swift targets either, it's currently only picked up for WASI. I'm inclined to rename that one to WASIToolchain maybe?
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Sorry I was wrong. A bit off-topic, but I think we might need to use WebAssemblyToolchain for all platforms using wasm-ld including Embedded WebAssembly targets because wasm-ld has quite different options set than other unix linkers. (e.g. wasm-ld doesn't have --start-group, all wasm targets needs --global-base, etc)
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@swift-ci test |
Embedded targets may need `-nostdlib` passed to `clang` linker driver in certain situations, see #1534 for more details. Currently, `swiftc` doesn't recognize `-nostdlib` at all, while `-Xlinker -nostdlib` passed to a `swiftc` link job from the build system will be passed verbatim to the linker and not recognized by the linker driver. We should support this flag in `swiftc` to fix this.
Depends on #1533.
Embedded Wasm binaries don't have compatible compiler-rt or C stdlib available, turn it off by default. Otherwise this makes trivial Embedded Wasm projects fail at link time.