wasm-linker: implement -fno-entry and correctly pass --shared and --pie when given
#17815
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Luukdegram
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andrewrk
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Nov 2, 2023
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Vexu
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Nov 2, 2023
andrewrk
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Nov 3, 2023
This adds support for the `-fno-entry` and `-fentry` flags respectively, for
zig build-{exe/lib} and the build system. For `zig cc` we use the `--no-entry`
flag to be compatible with clang and existing tooling.
In `start.zig` we now make the main function optional when the target is
WebAssembly, as to allow for the build-exe command in combination with
`-fno-entry`.
When the execution model is set, and is set to 'reactor', we now verify
when an entry name is given it matches what is expected. When no entry
point is given, we set it to `_initialize` by default. This means the user
will also be met with an error when they use the reactor model, but did
not provide the correct function.
When linking a WebAssembly binary using wasm-ld, we will now correctly pass --shared when building a dynamic library and --pie when `-fpic` is given. This is a breaking change and users who currently build dynamic libraries for WebAssembly but wish to have an executable without a main, should use build-exe instead while supplying `-fno-entry`. We also verify the user does not supply --export-memory when -dynamic is enabled. By default we set this flag now to 'false' when `-dynamic` is used to ensure we do not enable it as it's enabled by default for regular WebAssembly binaries.
This updates all linker tests to include `no_entry` as well as changes all tests to executable so they do not need to be updated later when the in-house WebAssembly linker supports dynamic libraries.
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Thanks for the feedback both Vexu and Andrew. I've pushed some changes which I think handles all cases now. Happy to hear if there are any other improvements to make. |
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Great work! |
peterhellberg
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Nov 7, 2023
Related to the breaking changes in ziglang/zig#17815
scheibo
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Nov 8, 2023
needing to explicitly list exports feels like a regression?
Pyrolistical
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Feb 27, 2024
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As discussed in #16949 (comment) this changes the invocation when building for the WebAssembly target. Users who previously used
-dynamicin combination withbuild-libwill now be required to usebuild-exein combination with-fno-entry. This is the same behavior as found in other compilers such as Clang and Rust.-fno-entrywill tell the linker there's no entry point available and therefore the built binary can be used, for instance, in a browser where no entry point is expected.This change also now correctly passes the
--sharedand--pielinker flags to wasm-ld when enabled in the frontend. e.g. when the user used the combination ofbuild-lib -dynamicorbuild-exe -fPIE.Closes #16937
Closes #16938
Closes #11045